Saving Seed: Will the seed produce plants similar to the plant it was collected from?
It can be very rewarding to harvest and save seed of ornamental and vegetable plants. But why is it that sometimes when we plant the seed we saved, the results do not seem to be very like the plant we collected the seed from?
To answer that question, it helps to know a little more about both the plant we collected the seed from, as well as the likely source of the pollen that fertilized the flower to form the seed.
When a seed is formed by a plant, it is the result of pollen fertilizing an egg (ovule). Whether the resulting seed “comes true,” that is, produces plants identical to the plant that it was harvested from, depends on whether it is outcrossed, inbred, or hybrid. These three options determine whether the two sets of genes (one from the pollen and one from the ovule) are likely to be identical or very different.
In inbred plants, the eggs are fertilized with pollen from the same plant. (Another term for this that you may have heard is self-pollination). The progeny will each have two identical (or nearly so) sets of genes, exact copies of their parents, and very similar to each other. Most peas and beans are inbred. Since seed from self-pollinated plants will produce plants very like the plant it was produced on, these kinds of plants are ideal for seed saving.
Outcrossed plants require pollen from a different plant to fertilize the egg (also called cross-pollination). Some outcrossing species have the female and male parts in separate flowers (corn or squash) or even separate plants (asparagus). Others have both parts in the same flower, but the egg will accept pollen only from another flower or plant. Apples are an example of this – that is why a separate pollinator tree is needed to obtain fruit. The two sets of genes in the offspring of outcrossed plants tend to have a lot of variation, so that the outcome of crossing is less predictable, somewhat like the variation between siblings in a human family. Seed from outcrossed plants will not necessarily come true; thus you should not save seed from these plants if you want to be certain that the plants will be exactly the same as their parents. However, if you have grown only one variety (and your neighbors have grown the same variety or are far enough away to avoid wind- or insect- cross pollination), you can still expect fairly consistent results from that seed.
Hybrids result from crossing two different inbred lines. All of the first generation of plants from this cross will contain the exact same two sets of genes (one from each line) and thus will be identical to each other. This first generation is what you buy in a seed packet marked “Hybrid” or “F1”. However, the next generation (the plants that will grow from seed produced from plants grown from “F1” seed) will contain a random mixture of genes, resulting in plants that may have a whole range of desirable and undesirable characteristics. Thus you should not save seed from F1 or hybrid plants if you want to be certain that the plants grown from that seed will be the same as their parents.
How can you tell whether a plant is outcrossed, inbred, or hybrid? First of all, look for the words “hybrid” or “F1” on seed packets. Any plant that has separate male and female flowers is most likely outbred. Plants with closed flowers, such as peas and beans, are usually inbred. Sometimes it will not be obvious whether the plant is inbred or outbred. Following is a list of plants that either mostly outcrossed or inbred.
There’s a Pepper Inside My Pepper!
We received an intriguing surprise the other night while prepping dinner. We cut open an unassuming bell pepper (Capsicum annuum) only to find a small, yet perfectly formed pepper inside! It seemed to be attached to the placenta along with the seeds. This was the first time we had ever encountered this, but a quick internet search revealed it isn’t necessarily a rare phenomenon. What was going on with this fruit that caused it to form another fruit within?
The quick answer is parthenocarpy or the formation of fruit without fertilization. Indeed, when we cut into this smaller pepper, there were no seeds inside. Some have taken to calling this phenomenon “internal proliferation,” but the question remained of what caused it to occur in the first place? It can be intentionally induced to produce seedless varieties of various fruits, however, given the “parent” pepper had plenty of seeds, this pepper within a pepper didn’t seem too intentional.
Another internet search revealed that this is an undesirable trait in the pepper trade. Pepper growers will actively select against plants that produce these internal proliferations. However, I have found it difficult to track down any real concrete explanations as to why it happens. Some have suggested that damage to the ovules or other external stressors such as temperature swings can occasionally induce them. Despite the validity of these hypotheses, few have actually bothered to collect and analyze any data.
I did find at least one paper that discussed something called “aberrant ovules” in peppers and their photographs certainly showed internal growths that looked a lot like what we observed in our pepper. These aberrant ovules ranged in appearance from what are essentially mini peppers to mutant blobs of colorful ovary tissue. The only sound conclusions I really took away from their work was that there does seem to be some evidence that genes are involved. They outlined an experiment in which some genetic lineages of peppers were significantly more likely to produce fruits with aberrant ovules than others. That being said, they did not venture much in the way of a trigger for inducing them. That was about as far as I got before I had to attend to other things in life like enjoying the meal we were making.
Regardless of the cause, it was an interesting and unexpected experience to open up this pepper only to find another pepper inside. We ended up eating the little fruit too, and it was just as yummy as the pepper that housed it!
The Carnivorous Plant Guild Welcomes a New Member
It is a rare but special day when we can add a new plant to the relatively small list of carnivorous plants. It is even more exciting when that plant has been “hiding” in plain sight all this time. Meet the western false asphodel (Triantha occidentalis), a lovely monocot native to nutrient-poor wetlands in western North America.
Triantha occidentalis may seem like an odd carnivorous plant. At first glance, it doesn’t have much in the way of carnivorous adaptations; there are not pitfall traps, no sticky leaves, no snap traps, and no bladders anywhere on the plant. However, if you were to examine this species during its flowering season, you would notice that a lot of small insects seem to get stuck to its flowering stem.
Indeed, the ability of this species to trap insects has been known for quite some time. Even old herbarium collections of T. occidentalis are chock full of insect remains stuck to the scape. Magnify the flowering stem and you will see that it is covered in sticky hairs or trichomes that look a lot like miniature versions of those covering the leaves of more obvious carnivores like sundews (Drosera spp.). Observations such as these led scientists to investigate whether this wonderful little wetland monocot actually benefits from trapping all those arthropods.
Via a series of experiments using isotopes of nitrogen, scientists have revealed that T. occidentalis really does obtain a nutritional boost from the insects it traps. This isn’t a passive process on the part of the plant either. It was also discovered that the plant also secrets the digestive enzyme phosphatase, which helps break down the trapped insects. When the team examined what was going on within the tissues of the plant, they found even more evidence of its carnivorous nature.
Look closely and you can see sticky glands and trapped insects just below the flowers! Photo by Michael Kauffmann (www.backcountrypress.com)
It turns out that 64% of the nitrogen within the plant is obtained via insect digestion, which is comparable to that of other known carnivorous plants such as the aforementioned sundews. Interestingly, it appears that the insect nitrogen the plant obtains is first stored in the flowering stem and fruits but is then transported down into the roots and rhizome underground to be utilized in the following growing season. Why exactly the plant does this requires further investigations. Perhaps by using its flowering stems to obtain nutrients that are in short supply in its wetland habitat, the plant is able to better offset the cost of flowering each year.
By far the most remarkable aspect of this discovery is where carnivory occurs on the plant. With few exceptions, the vast majority of carnivorous plants keep their feeding organs away from their flowers. The leading hypothesis on this suggests that separating feeding and reproduction in space (and sometimes time) helps carnivorous plants avoid catching and digesting their pollinators. However, T. occidentalis does the opposite. It produces all of its sticky hairs very close to its blooming flowers.
Large floral visitors like butterflies appear to be the main pollinators and are too large to get stuck, whereas smaller insects like midges do. Photo by Michael Kauffmann (www.backcountrypress.com)
The key to this apparent morphological contradiction may lie in the stickiness of those hairs. It has been observed that the vast majority of insects trapped on the flowering stems of T. occidentalis are mostly midges and other small insects that don’t function as pollinators for the plant. It is possible that the larger bees and butterflies that could function as true pollinators are simply too large and strong to be trapped. Again, more research is needed to say for sure.
All in all, T. occidentalis represents a unique carnivorous plant whose true nature required solid natural history knowledge and observation to reveal. The fact that we are just learning about its carnivorous habit after all this time suggests that many more potentially carnivorous plants may also be “hiding” in plain sight (I’m looking at you, Silene), waiting for curious minds to collect the necessary data. This is also an exciting discovery from a taxonomic perspective as well. Up until now, all of the known carnivorous monocots hail from the order Poales. Therefore, T. occidentalis represents the first non-Poalean carnivorous monocot! For all these reasons and more, I am excited about future research on this plant and others like it.
An Endemic Spurge in Florida
A pistillate cyathium of a Telephus spurge.
Endemism fascinates me. Why some organisms occur in certain restrict areas geographically and nowhere else is such a fun topic to ponder. On a recent trip to the Florida Panhandle, I was lucky enough to encounter a wonderful little plant endemic to pine flatwoods located at the very tip of the Apalachicola region. It is a type of spurge known as Telephus spurge (Euphorbia telephioides) whose natural history is captivating to say the least.
The Telephus spurge is a denizen of dry, sandy soils. Its fleshy leaves and deep, tuberous taproot not only allow it to handle drought via the storage of water and nutrients, its root system also allows it to live a long time. Though it is hard to say how long individuals can actually live, lifetimes measured in decades are well within the realm of possibility. Like many members of the spurge family (Euphorbiaceae), the Telephus spurge is also well defended by toxic, milky sap.
A staminate cyathium of a Telephus spurge.
The inflorescence of the Telephus spurge is defined as a cyathium. Plants can produce multiple cyathia per plant, and for the Telephus spurge, these can contain only male, only female, or both reproductive structures. Sex of individual Telephus spurge is an interesting topic unto itself and very important when it comes to conservation (more on that in a bit). Individual Telephus spurge can be fluid in their sexual expression from one year to the next. Individuals that produced only male cyathia one year can go on to produce only female or bisexual cyathia in subsequent years. No one can say for sure what triggers these changes among individuals, but disturbance and energy reserves likely play a considerable role.
One of the most important aspects of Telephus spurge ecology is fire. Without regular fires, the entire habitat of the Telephus spurge would gradually close in with woody shrubs and trees and disappear. Even though most of the top parts of these plants are killed by fires, their large tuberous root system allows them to readily regrow what was lost. That is not to say that individuals regularly regrow after fires. In fact, plants have been known to disappear for years at a time following top killing events, only to resprout at some point in the future when favorable conditions return.
Telephus spurge fruits are quite pretty!
At this point, it should be obvious that for this species to persist, its habitat needs to be maintain via fire. Management for this species is very important given its narrow distribution and sporadic occurrence on the landscape. However, there are still many hurdles in the way of effective Telephus spurge conservation. For starters, though it once likely enjoyed a more contiguous distribution throughout the Apalachicola region, habitat destruction from logging, ditching, and development have highly fragmented its populations into tiny clusters. The smaller these clusters become, the more vulnerable they are to extirpation.
Another factor complicating the conservation of this species is its aforementioned sexual fluidity. Because we still don’t know what triggers a change in sexual expression among individuals from one year to the next, populations can fluctuate greatly in terms of their reproductive capacity. For instance, if a population comprised of many individuals with bisexual cyathia one year suddenly switches to producing mostly male cyathia the following year, seed production can decrease greatly. Until we know more about the reproductive ecology of this species, maintaining populations with regular fire while limiting the amount of logging and development is the best chance we have at ensuring this extremely rare spurge has a future on this planet.
The one upside to this story is that, where properly managed, Telephus spurge can reach high abundances. With a little bit of effort, these populations are relatively easy to map and seed can be collected and maintained to preserve valuable genetic material. Still, without proper management and land conservation/restoration efforts, the future of this tiny spurge and many of its botanical neighbors hangs in the balance. Support your local land conservancy today, because stories like this are far more common than you think!
Pitcher Plant Moths and their Pitcher Plant Homes
Discussions about pitcher plants usually revolve around the fact that they trap and eat insects and other animals. However, there are a handful of organisms out there that turn the table on pitcher plants, reminding us that these botanical carnivores can become food themselves. Spend any amount of time surveying pitcher plant populations in southeastern North America and you are likely to encounter at least one such species of pitcher plant eater.
There are three species of pitcher plant moths in the genus Exyra and all of them would not exist if it were not for pitcher plants in the genus Sarracenia. Whereas E. ridingsii and E. semicrocea are largely restricted to southeastern portions of North America, E. fax can be found as far north as Newfoundland. These three species also vary in their dietary specificity. As you can probably ascertain from its distribution, E. fax is a purple pitcher plant (S. purpurea) but will also feed on the southern pitcher plant (S. rosea) in the southern portions of its range. Exyra ridingsii is also a dietary specialist, feeding only on the pitchers of the yellow pitcher plant (Sarracenia flava). Alternatively, E. semicrocea is a generalist and can be found feeding on a variety of Sarracenia species.
An Exyra caterpillar busy feeding on a Sarracenia flava pitcher.
Both caterpillars and adult moths are physically adapted to living within the slippery interior of the pitcher walls. Microscopic analyses of their feet have revealed specialized morphological adaptations that allow them to cling to the waxy walls of the pitcher. The caterpillars may also benefit from their ability to spin silken lines. Interestingly, the moths are only ever found perched upright in the pitchers. Even when they mate (which also occurs within the pitcher), they do so at a 90 degree angle so that neither partner is facing downward. It is thought that they must remain mostly upright in order for their feet to properly cling to the waxy wall.
Regardless of which pitcher plant they are eating, these three moths all behave similarly throughout their lifecycle. The caterpillars are hatched within a pitcher. Immediately they begin feeding on the wall of the pitcher. They will only eat the interior cells of the pitcher wall, leaving a thin layer of tissue on the outside wall. This makes the pitcher look as if it is covered in translucent, brown windows. At some point in their development, the caterpillars will also spin a layer of silk over the mouth of the pitcher. This protects them from predators like lynx spiders and cuts off the pitchers ability to capture prey (more on this in a bit).
As the caterpillars grow, they will occasionally move to new pitchers. At larger sizes, their feeding damage can be quite extensive, damaging the walls of the pitcher to the point that it loses its structural integrity and folds over. This can also serve to protect the caterpillar from predators while similarly reducing the ability of the plant to capture food. After their fifth larval instar, the caterpillars will move to a new, usually undamaged pitcher. In many instances, they will crawl to the bottom and chew a small hole in the side, draining the pitcher of its digestive fluids. They will then pupate just above the drainage hole.
Signs of Exyra feeding damage.
After a period of time that varies between species, adult moths will emerge. The adults are adorable little critters dressed in shades of yellow and black. They are also very secretive and do not leave the pitchers until nightfall. Even then, they only do so to mate and lay eggs in new pitchers. After mating, the female will lay her eggs just below the mouth of a new pitcher and the cycle begins anew. Amazingly, it has been found that the only other stimulus besides the urge to mate that can coax the moths to leave their pitchers is smoke. This is especially true for the southern species as the bogs in which they live are subject to frequent fires. If they were to remain in the pitchers, it is likely that entire populations would be incinerated.
As terrifying as this sounds for the moths, fire is essential to their lifecycle. The pitcher plant bogs of southeastern North America could not persist without fire. When fires are suppressed, these bogs inevitably fill in with more aggressive vegetation such as swamp titi (Cyrilla racemiflora) or any of the myriad invasive species that grow in this region. As bogs become choked with woody shrubs and trees, pitcher plants and other bog species are choked out to the point that they can completely disappear. Fire in these habitats brings more life than it does death.
A population of Sarracenia flava var. rubricorpora showing signs of a thriving Exyra moth population in the form of damaged and bent over pitchers.
Given that the pitchers of pitcher plants function as both photosynthetic organs and a means to obtain nutrients like nitrogen and phosphorus, it stands to reason that damage from pitcher plant moths could harm the plants over the long term. Indeed, high densities of pitcher plant moths can exact quite a toll on pitcher plant individuals. Evidence from multiple sites has shown that heavily damaged pitcher plants can shrink in size over time, indicating loss of energy reserves. In support of this, some have also found that highly damaged pitcher plants go on to produce more pitchers, which indicates that such individuals are prioritizing more nutrient capture. In ecosystems already defined by nutrient scarcity, the effects of herbivory on these carnivorous plants are likely more severe than they are for plants growing in nutrient-rich environments. However, it should be noted that it is a rare case in which pitcher plant moths exact such a toll on plants as to completely kill the pitcher plants they rely on for survival.
That being said, there is plenty of room for concern over the future of both pitcher plants and moths. Only 3% of the bogs that once existed in southeastern North America remain today. Habitat loss means fewer populations of plants and thus less habitat for the moths (and myriad other lifeforms) that rely on them. For these reasons and more, habitat protection and restoration must be made a high priority moving into the future. Please consider supporting a land conservation/restoration organization in your area!
My Unforgettable Encounter with a Fevertree
When someone asks you if you would like to see a wild fever tree, you have to say yes. As a denizen of cold climates defined by months of freezing temperatures, I will never miss an opportunity to encounter any species in its native habitat that cannot survive frosts. This was the scenario I found myself in last week as friend and habitat restoration specialist for the Atlanta Botanical Garden, Jeff Talbert, was showing us around a wonderful chunk of Florida scrubland he has been managing over the last few years.
He drove our small group over to an area that, up until a year or two ago, was completely choked with swamp titi (Cyrilla racemiflora). Like many habitats throughout southeastern North America, this patch of Florida scrub is dependent on regular fires to maintain ecological function. Without it, aggressive shrubs like titi completely take over, choking out much of the amazing biodiversity that makes this region unique. Jeff and his team have been very busy restoring fire to this ecosystem and the results have been impressive to say the least.
We walked off the two-track, down into a wet depression and were greeted by an impressive population of spoon-leaf sundews (Drosera intermedia), which is a good sign that water quality on the site is improving. After a few minutes of sundew admiration, Jeff motioned for us to look upward towards the surrounding tree line. That’s when we saw it. Growing up out of the small seep that was feeding this wet depression was a spindly tree with bright pink splotches decorating its canopy. This was to be my first encounter with a fevertree (Pinckneya bracteata).
A few of us were willing to get our feet wet and were rewarded with a close look at the growth habit of this incredible tree. Clustered at the end of its spindly branches are dark green, ovate leaves that give the tree a tropical appearance. Erupting from the middle of some of those leafy branches were the inflorescences. These are what produce the pink splotches I could see in the canopy of larger individuals. They remind me a lot of a poinsettia and at first, I thought this tree might be a member of the genus Euphorbia. Indeed, the pink coloration comes from a handful of rather large, leaf-like sepals attached to the base of each inflorescence.
Upon seeing the flowers, I instantly knew this was not a member of Euphorbiaceae. Each flower was long and tubular ending in five reflexed lobes. They are colorful structures in and of themselves, adorned with splashes of pink and yellow. After a bit of scrutiny, our group was finally able to place this within its true taxonomic lineage, the coffee family (Rubiaceae).
Within the coffee family, fevertree is closely related to the genus Cinchona. Like Cinchona, the fevertree produces quinine and other alkaloids that are effective in treating malaria. Fevertree has been used for millennia to do just that, hence the common name. It also seems fitting that fevertrees tend to grow in wetland habitats where mosquitos can be abundant. However, this is by no means an obligate wetland species. Those who have grown fevertree frequently succeed in establishing plants in dry, upland habitats as well. Perhaps highly disturbed wetlands are some of the few places where this spindly tree can avoid intense competition from other forms of vegetation.
Fevertrees do need regular disturbance to persist. They are not a large, robust tree by any means and can easily get outcompeted by more aggressive vegetation. However, this species does have a trick that enables individuals to persist when disturbances don’t come frequent enough. Fevertree is highly clonal. Instead of producing a single trunk, it sends out numerous stems in all directions in search of a gap in the canopy. This clonal habit allows it to eek out an existence in the gaps between its more robust neighbors until disturbances return and clear things out.
This clonal habit is also very important when it comes to reproduction. Fevertree requires a decent amount of sunlight to successfully flower and set seed. By using its clonal stems to find light gaps, it can at least guarantee some level of reproduction until fires, floods, or some other form of canopy clearing disturbance frees up enough space for it to prosper and its seeds to germinate. However, its clonal habit can also hurt its reproductive capacity over the long term if recruitment of new individuals does not occur.
Fevertree is considered self-incompatible. In other words, its flowers cannot be pollinated via pollen from a genetically identical individual. As more and more clonal shoots are produced, the tree effectively increases the chances that its own pollen will end up on its own flowers. This is yet another important reason why regular disturbance favors fevertree reproduction. Fevertree seeds need light and bare ground to germinate, which is usually provided as fires and other disturbances clear the canopy and open up bare ground. Only then can enough unrelated individuals establish to ensure plenty of successful pollination opportunities.
With its long, tubular flowers and bright pink sepals, fevertrees don’t seem to have any trouble attracting pollinators, which mainly consist of ruby-throated hummingbirds and bumblebees. Only these organisms have what it takes to successfully access the pollen and nectar rewards of this plant and travel the distances necessary to ensure pollen ends up on unrelated individuals. The seeds that result from pollination are winged and can travel a decent distance with a decent wind. With any luck, a few seeds will end up in another disturbance-cleared wet area and usher in the next generation of fevertrees.
I am so happy that restoration activities at this site are making more suitable habitat for this unique tree. Looking around, we saw many more small individuals starting to emerge where there was once a dense canopy of titi. Hopefully with ongoing management, this population will continue to grow and spread, securing the a future for this species in a region with an ever-growing human presence. If you ever find the opportunity to see one of these trees in person, do yourself a favor and take it!
Bearcorn: A Mysterious Parasite from Eastern North America
Bearcorn (Conopholis americana) is one of those plants that really challenges mainstream assumptions of what a plant should look like. It produces no leaves, no chlorophyll, and all you ever see of it are its strange reproductive structures. One can easily be forgiven for thinking they had encountered some type of fungus.
Bearcorn is an obligate parasite on oak trees. It simply can’t exist without access to oak roots. From what I have been able to gather, the preferred hosts of bearcorn are the red oaks (section Lobatae). That is not to say the exceptions have not been documented. At least one author claims to have found bearcorn attached to the roots of a white oak (Quercus alba) and even earlier work suggests that American chestnut (Castanea dentata) may have served as an occasional host as well. Regardless, if you want to find bearcorn in the woods, you would do well to search out red oaks first.
According to those who have run germination trials, bearcorn seeds must be in close proximity to oak roots in order to germinate. Some sources say that direct contact is needed whereas others claim that seeds have to be close enough to detect root presence. It is likely that some sort of chemical cue is what initiates the process and this makes sense. For a plant that relies completely on another plant for its water and nutritional needs, it doesn’t make much sense for bearcorn seeds to germinate anywhere but near oak roots.
Upon germinating, the tiny seedling needs to act fast before its meager energy reserves are exhausted. If lucky, the growing seedling will come into contact with an oak root and begin developing a strange organ referred to as the nodule or tubercle. Thus begins its parasitic lifestyle. The tubercle continues to grow throughout the life of the plant, developing into an amorphous, woody blob that continues to envelope more and more oak roots. Its within the tubercle that all of the parasitism takes place.
Cells within the bearcorn tubercle penetrate into the vascular tissues of the oak root, stealing all the water and nutrients the plant will ever need. Over time, the bearcorn tubercle coaxes the roots of the oak to fan outward like the crown of a tiny tree. In doing so, bearcorn is effectively increasing the amount of surface area available to make more parasitic connections. Apparently this all comes at great cost to the oak roots. Over time, oak root size within the tubercle greatly diminishes until some completely perish. Considering the size of some bearcorn populations, one could expect the oak host to fight back.
Indeed, it would appear that oaks are not helpless against bearcorn infestations. Examination of the cells within bearcorn tubercles revealed that as the parasite grows, the oak will begin flooding the infected cells with tannin-rich compounds. Apparently this serves to slow the flow of water and nutrients into the tubercle. There is even evidence that some of those tannins are transferred into the bearcorn tubercle, leading some to suggest that the oak is literally poisoning its bearcorn parasites, albeit slowly.
There is a strong possibility that such oak defenses lend to the relatively short lifespan of bearcorn plants. In at least one study I read, no bearcorn individuals over 13 years of age were found and the average age is estimate to be about 10 years. Perhaps just over a decade is about all a bearcorn can hope for once the its oak host begins to fight back. Good thing bearcorn populations can be surprisingly fecund.
Bearcorn plants reach reproductive maturity at after about 3 years of growth. They flower in the spring and that is when they are at their most obvious. Numerous thick, finger-like stems emerge from the ground covered in whirls of cream-colored, tubular flowers. Though a dense population of flowering bearcorn may look like a bonanza for pollinators, they don’t seem to attract a lot of attention. From what I was able to find, bumblebees are pretty much the only insects to visit the flowers, and even then, visitation rates are low. Apparently bearcorn flowers do not produce any detectable scent nor are they full of nectar. I guess the only real reward is a meager helping of pollen.
Photo by Joshua Mayer licensed under CC BY-SA 2.0
No matter, bearcorn has a nice reproductive trick to ensure plenty of seeds are produced each year – it selfs. The anatomy of the flowers is such that, at maturity, the anthers are in direct contact with the stigma. Even if nothing visits a bloom, it will still go on to clone itself year after year. Once fertilized, each flower gives way to a large fruit chock full of seed. This is where the corn part of the name bearcorn comes from. A stem thick with fruits does resemble a strange, albeit juicy ear of corn sitting on the forest floor. The bear part of the name likely has to do with the fact that bear readily consume bearcorn fruits, stem and all. Working in the southern Appalachian Mountains, I can’t tell you how many times I came across bear scat absolutely loaded with bearcorn fruits and seeds. It’s not just bear either, deer are also very interested in bearcorn fruits.
Lucky for bearcorn, its seeds pass through the guts of these animals unharmed. Hopefully, with a bit of luck, at least one of these animals will make a deposit in an oak-rich region of the forest. With even more luck, some of those seeds might even find themselves nestled in near an oak root to begin the process anew.
A North American Lily-of-the-Valley?
The flora of the southern Appalachian Mountains will never cease to amaze me. Every time I visit this region of the world, I am blown away by the sheer number of plant species that grow on and around these ancient peaks. On a recent trip to western North Carolina, I stumbled across a small group of plants that somehow looked both familiar and strange at the same time. It turns out that I had crossed paths with a species that, up to that point, I thought was just a rumor.
Growing up, lily-of-the-valley was a very common sight. It seemed that everyone I knew was growing a dense patch of these wonderfully fragrant, spring bloomers. Indeed, lily-of-the-valley is an extremely popular garden plant that has found a place in many a cool, temperate garden around the world. It is known to science as Convallaria majalis and is native throughout Eurasia. Its popularity in the garden has seen that range expand in a big way. In fact, Eurasian lily-of-the-valley’s habit for aggressive clonal spread has made it into an invasive species in many locations.
Perhaps this is why I (as well as many others) never paid much attention to the genus. For some time, only C. majalis was considered to be valid. All other plants were written off as individuals or populations that had managed to escape from cultivation. Certainly, this isn’t too far off the mark in many cases as the remains of old homesteads are often outlived by robust populations of garden plants that once decorated their foundation. As such, plants like C. majalis are all too readily overlooked when encountered in places that don’t necessarily represent a present-day garden bed. Indeed, as recently as the 1980’s and 90’s, botanical authorities dismissed all populations of Convallaria outside of Eurasia as early garden escapees no matter how different they looked or how isolated they grew.
That is not to say that familiarity with a garden plant can’t lead to new insights. Indeed, the fact that I am so overly-familiar with gardens full of C. majalis was the main reason why my recent encounter in southern Appalachia conjured feelings of familiarity and novelty at the same time. I was hiking with friends near around 4,000 ft (
1,200 m) in elevation when we crested a small ridge. Tucked in among the rocks were a small group of monocots that, at first glance, looked like C. majalis. However, the more I looked at them, the more something felt off.
These plants were surprisingly tall and lanky. Their leaves were not nearly as broad either. Upon closer inspection, I realized a few were in bloom. Whereas the small white flowers on each inflorescence were carbon copies of those of the more familiar C. majalis, the entire inflorescence was very short. I am used to lily-of-the-valley flowers presented up above the leaves but those on the plants in front of me topped out well below leaf level. This odd combination of characters jogged a memory of a conversation I had in passing years ago. I forget who I was talking to and most of what was said, but something in the back of my mind remembered something about a native lily-of-the-valley. We took some pictures and kept hiking but I was excited to get back and see what my botanical key had to say.
Upon consulting Weakley’s Flora of the Southeastern United States, I found that what we had seen and photographed were not a rumor but an actual species! The plants keyed out to Convallaria pseudomajalis or American lily-of-the-valley. I was beside myself that I could have been so unaware of such a wonderful species. I got on the internet and tried to find out more, but that is where I hit some major road blocks. It turns out, there isn’t much readily available on this plant.
A large part of the issue stems from the fact that, as mentioned above, many had written this species off as nothing more than escaped representatives of C. majalis. Even among those who did pay enough attention to consider C. pseudomajalis a distinct species, there seems to be plenty of confusion over what to call it. Some sources list it as C. montana, however, this name is now considered illegitimate. Others call it C. majuscula whereas other sources list it under C. pseudomajalis. There is no denying that such taxonomic confusion makes tracking down resources on this plant a difficult task. Add that to the fact that outside of taxonomy and field botany, seemingly no one has done any ecological work on the plant and you find yourself in the same seat as me – excited but confused.
What little information I could track down does make me feel very confident that C. pseudomajalis is indeed a true species and not an escaped version of C. majalis. For starters, with even the slightest bit of scrutiny, there is no denying these plants are morphologically distinct. Also, the habitats in which C. pseudomajalis is found are quite isolated, even for a garden escape. For starters, C. pseudomajalis can only be found in the southern Appalachian Mountains growing at elevations between
4,900 feet (1,000 – 1,500 m) along rocky ridges. These sorts of places don’t jump out as sites of old homesteads. Also, C. pseudomajalis populations hardly ever reach the density one sees with C. majalis in most instances. Coupled with the isolated nature of C. pseudomajalis populations, it would take a lot more convincing for me to fall into the “escaped from cultivation” camp.
Taken together, I feel pretty confident in saying I finally got to meet North America’s native lily-of-the-valley. It was a very exciting find that occurred in a very beautiful part of the world and I am happy to know this plant exists. Perhaps one day, some intrepid scientist will turn their focus onto C. pseudomajalis and be able to provide us with deeper insights into its biology, ecology, and status in this ever-changing world.
When Trillium Flowers Go Green
The first time I encountered a white trillium (Trillium grandiflorum) with green stripes on its flowers, I thought I had found a new variant. I excitedly took a bunch of pictures and, upon returning home, shared them among friends. It didn’t take long for someone far more informed than me to point out that this was not a new variant of this beloved plant. What I had found was signs of an infection.
The green stripes on the petals are the result of a very specific bacterial infection. The bacteria responsible belongs to a group of bacterial parasites collectively referred to as phytoplasmas. Phytoplasmas are not unique to trillium. In fact, these bacteria can be found around the world and infect many different kinds of plants from coconuts to sugarcane. Indeed, most of the research on phytoplasmas is motivated by their impacts on agriculture. Despite the damage they can cause, their natural history is absolutely fascinating.
Phytoplasmas are obligate parasites. They can only live long-term inside the phloem of their preferred host plants. Once inside the plant, phytoplasmas begin tinkering with cell expression, causing an array of different symptoms that (to the best of my knowledge) depend on their botanical host. In the case of trillium, phytoplasma infection causes a change in the flower petals. By altering gene expression, petal cells becoming increasingly leaf-like, resulting in the green striping I had observed. That isn’t all the phytoplasma does either. Infections usually result in complete sterilization of the flower. I have even heard some reports that the infected plants are also weakened to the point that they eventually die.
Why the phytoplasma do this has to do with their bizarre life cycle. Now, to be fair, much of what I have been able to gather on the subject comes from research done on other plant species. Still, there are enough commonalities among phytoplasma infections that I strongly suspect they apply to the trillium system as well. Nevertheless, take what I am saying here with a grain of salt.
As mentioned, phytoplasma can only exist long-term within the phloem of their plant host. They don’t produce any sort of fruiting bodies, nor are they transferred by air or contact with tissues. This creates a bit of an issue when it comes to finding new hosts, especially if infection inevitably results in the death of the plant. This is the point in which a vector must enter the picture.
The vector in question in many cases are sap-feeding insects like leafhoppers. Leafhoppers use their needle-like proboscis to pierce the phloem and suck out sap. It’s this feed behavior that phytoplasma capitalize on to complete their lifecycle. Moreover, the phytoplasma don’t do so passively. Just as the phytoplasma alter the gene expression in the petal cells, they can also alter the expression of genes involved in plant defenses.
Research on infected Arabidopsis plants has shown that phytoplasma cause the plant to decrease production of a hormone called jasmonate. This is fascinating because jasmonate is involved in defending plants against herbivory. It was found that when plants produced less jesmonate, leafhoppers were 30%-60% more likely to lay eggs on those plants. Essentially, the phytoplasma are reducing the plants’ defenses in such a way that there is a greater chance that they will be fed on by a greater number of sap-suckers.
As leafhoppers feed on the sap of infected plants, they inevitably suck up plenty of phytoplasma in the process. Through a complex series of events, the ingested phytoplasma eventually make their way into the salivary glands of the leafhopper. Then, as the leafhopper moves from plant to plant, piercing the phloem to feed, it inevitably transfers some of the phytoplasma in its saliva into a new host, thus completing the lifecycle of these plant parasites.
To bring it back to those green stripes on the trillium flowers, I suspect that by altering the petal cells to look more like leaves, the phytoplasma may be “encouraging” leafhoppers to concentrate their feeding on infected tissues. However, this is purely speculation on my part. The lack of data outside the agricultural realm represents an important scientific void that needs filling.
Roadside Seeding and Bluebonnet Genetics
Photo by Adam Baker licensed under CC BY-NC 2.0
The mass blooming of bluebonnets (Lupinus texensis) is truly one of southern North America’s most stunning natural spectacles. Celebrated across its native range, the bluebonnet has greatly benefited from supplemental planting by humans. Indeed, in states like Texas, hundreds of miles of roadsides are seeded with bluebonnets every year and the end result can be spectacular. The popularity of mass seeding of this wonderful species has led some to ask how the practice may be affecting the genetic diversity of the species throughout its range.
Before we get into population genetics, it is worth getting to know this plant a bit better. Bluebonnets are a type of winter annual lupine endemic to southern Texas and northern Mexico. Their highly camouflaged seeds usually begin to germinate late in the fall after enough weathering has weakened the hard seed coat the protects the embryo. Seedlings remain small throughout fall and winter, rarely growing more than a few tiny, palmate leaves. Once spring arrives, growth accelerates.
Within a few short weeks, most individuals will have already pushed up a spike chock full of their characteristic blue and white flowers. Their main pollinators are bumblebees such as the American bumblebee (Bombus pensylvanicus). Once pollinated, plants don’t waste any time producing seeds. Bluebonnets utilize an explosive seed dispersal mechanism, which can be pretty fun to witness in person. As the pods mature, they gradually dry out, creating a lot of tension. Eventually, the tension within the pod becomes so great that the whole structure gives in and explodes, launching seeds as far as 13 feet (4 m) away from the parent plant where they will wait until fall returns.
Although 13 feet may sound like a decent distance for a plant the size of a bluebonnet to launch its seeds, it pales in comparison to many other forms of seed dispersal. As such, one would expect bluebonnets within any given population to be more closely related to one another than they would be to bluebonnets growing in other, more distant populations. It is this assumption that led scientists to ask how intentional seeding of bluebonnets may be affecting the genetics of these plants. Before we jump into their findings, I first want to make one thing very clear.
I am in no way disparaging intentional seeding of native plants, especially not by municipalities! I think the practice of seeding with native plants is vital to any environmental management practice we humans undertake. That being said, it is important that we try to understand how any of our actions may be impacting any aspect of biodiversity. Now, onto the research.
By sampling the DNA of both natural and intentionally planted populations across a wide swath of bluebonnet’s endemic range, scientists revealed an intriguing picture of their genetic structure. Simply put, there is surprisingly little. Where they expected to find genetic differences among populations, they instead found a lot of uniformity. It is almost as if populations were mixing their genetic material across the range of the species.
There are a few possible explanations that could explain this pattern. For one, it is possible that estimates of seed dispersal in this species are vastly underestimated. Perhaps seed dispersal events regularly exceed previous estimates of around 13 feet. Along a similar line of reasoning, it is also possible that bluebonnets don’t rely solely on ballistics to get their seeds out into the environment. If birds or mammals occasionally move seeds long distances, this could eventually lead to genetic mixing among different populations. However, such possibilities are unlikely given the nature of bluebonnet seeds and the fact that animals are far more likely to act as seed predators for bluebonnets than seed dispersers.
Scientists have also put forth the possibility that bluebonnets in both natural and cultivate populations simply haven’t been isolated long enough for genetic differences to emerge among populations. However, this does not explain why there is so few genetic differences among widely separated natural populations.
The most likely reason why bluebonnets are so alike genetically is intentional planting. Though plenty of effort is put into ensuring that bluebonnet plantings are done using seeds sourced within 124 miles (200 km) from the planting site, we simply can’t rule out the idea that genes from individuals sourced from cultivation are not completely swamping the gene pools of wild populations as they are sowed along roadsides and into other planting projects.
To be fair, though these findings are compelling, we can’t necessarily jump to any conclusions as to whether such genetic swamping is a net negative or net positive for bluebonnets across their range. The scientists involved with the study do mention that swamping of fractured wild bluebonnet populations with genes of cultivated individuals could prove beneficial for the species, especially as the impact of human development continues to increase. It is possible that cultivated individuals that are selected because they perform well in human-dominated environments are introducing genes into wild populations that may allow them to cope with the increased human disturbances.
The alternative argument to that point is that we are swamping wild populations with potentially deleterious alleles at a faster rate than natural selection can purge them from the population. If this is the case, we may see a gradual decline in some populations that grow more and more out of sync with their local environment.
Though it is far too early to draw any hard fast conclusions about the impacts of genetic swamping, the genetic patterns that have been uncovered among bluebonnets are important to document. Now that we know that genetic diversity is low across populations, we can begin to dive deeper into both the mechanisms that created said patterns and their impacts on various populations. Once again, this is not an argument against intentional seeding and planting of native plants. Instead, it is a nice reminder that even the best intentions can have vast and unintended consequences that we need to study in more detail.
The American Smoketree
Photo by Andrew Ward licensed under CC BY-NC 2.0
I am a sucker for smoketrees (Cotinus spp.). These members of the cashew family (Anacardiaceae) are a common sight around my town and really put on a dazzling show from late spring through fall. When I finally got around to putting a name to these trees, I was a little bit bummed to realize that all of the specimens in town are representatives of the Eurasian species, Cotinus coggygria, but it didn’t take me long to find out that North America has it’s own fascinating representative of the genus.
The American smoketree (Cotinus obovatus) is not terribly common in the wild or cultivation. Today, it exhibits a suffuse distribution through parts of southern North America, with disjunct populations occurring along the Ozark Plateau of Arkansas and Missouri, the Arkansas River in eastern Oklahoma, the Cumberland Plateau in northeastern Alabama, Tennessee, and Georgia, and the Edwards Plateau in west-central Texas. The major habitat feature that unites these populations is soil. All of them are said to grow on rocky, calcareous soils prone to drought.
Photo by Megan Hansen licensed under CC BY-SA 2.0
It is an interesting distribution to say the least. I haven’t found too much in the way of an explanation for why the American smoketree is limited to calcareous soils in the wild. Apparently it is fairly adaptable to different soil types in cultivation. Perhaps competition with other species limits this tree to harsh conditions. It isn’t a big species by most standards. The American smoketree generally produces multiple stems and only occasionally reaches heights of 30 feet (9 meters) or more in most circumstances. One phrase that gets repeated with some frequency is that the American smoketree likely represents a relictual species.
Though hard to prove without ample fossil evidence, it seems many experts believe that American smoketrees (and the genus Cotinus in general) were far more common and widespread in the past than they are today. Indeed, the fossil remains of a species named Cotinus cretaceus (sometimes C. cretacea) were found in Alaska and date back to the late Cretaceous. Given that the American smoketree’s closest living relatives are found throughout parts of Europe and Asia, such evidence suggests that this genus spread into North America during a period when land bridges connected the two continents and has since been reduced to scattered populations of this single North American species.
Photo by Andrey Zharkikh licensed under CC BY 2.0
European colonization of North America did not help the American smoketree either. American smoketree sap can be processed into a yellow dye, which was highly coveted during the American Civil War. Its rot-resistant wood was also widely used for fence posts. At least one source I found indicated that the tree was cut to near extirpation in many areas for these reasons. Luckily today, with harvesting pressures largely a thing of the past, the American smoketree has rebounded enough that it is currently considered a species of least concern.
The American smoketree has also benefited from some minor popularity in cultivation. Like its Eurasian cousins, the appeal of this species comes from its colorful foliage, wonderfully flaky bark, and billowy inflorescences. Its egg-shaped leaves emerge in spring and are silky and pink. As spring gives way to summer, the leaves gradually turn a pleasing shade of blueish-green. Come fall, the leaves paint the landscape in bright red until they are shed. Late spring is generally the blooming time for American smoketree.
Photo by peganum licensed under CC BY-SA 2.0
Its tiny, inconspicuous flowers are borne on large, branching panicles. Each panicle is covered in tiny hairs that apparently continue to grow well after the flowers have been pollinated. This is where the name smoketree comes from. From afar, a tree covered in panicles looks as if it is billowing dense clouds of smoke from its canopy. The whole spectacle is stunning to say the least and I just wish this species was more popular than its cousins.
All in all, the American smoketree is a truly interesting species. From its fractured distribution and curious history to its status as an obscure native tree in cultivation, there are a lot of reasons to love this species. Though related to plants like poison ivy (Toxicodendron spp.), smoketrees only rarely cause dermatitis in particularly susceptible individuals. I hope I get the chance to see an American smoketree in the wild some day.
The Future of New Zealand’s Shrubby Tororaro Lies in Cultivation
Photo by Jon Sullivan licensed under CC BY-NC 2.0
I was watching a gardening show hosted by one of my favorite gardeners, Carol Klein, when she introduced viewers to a beautiful, divaricating shrub whose branching structure looked like a dense tracery of orange twigs. She referred to the shrub as a wiggy wig and remarked on its beauty and form before moving on to another wonderful plant. I was taken aback by the structure of the shrub and had to learn more. Certainly its form had to be the result of delicate pruning and selective breeding. Imagine my surprise when I found its growth habit was inherent to this wonderful and rare species.
The wiggy wig or shrubby tororaro is known to science as Muehlenbeckia astonii. It is a member of the buckwheat family (Polygonaceae) endemic to grey scrub habitats of eastern New Zealand. Though this species is widely cultivated for its unique appearance, the shrubby tororaro is not faring well in the wild. For reasons I will cover in a bit, this unique shrub is considered endangered. To understand some of these threats as well as what it will take to bring it back from the brink, we must first take a closer look at its ecology.
Photo by WJV&DB licensed under CC BY-SA 3.0
As mentioned, the shrubby tororaro is endemic to grey scrub habitats of eastern New Zealand. It is a long lived species, with individuals living upwards of 80 years inder the right conditions. Because its habitat is rather dry, the shrubby tororaro grows a deep taproot that allows it to access water deep within the soil. That is not to say that it doesn’t have to worry about drought. Indeed, the shrubby tororaro also has a deciduous habit, dropping most if not all of its tiny, heart-shaped leaves when conditions become too dry. During the wetter winter months, its divaricating twigs become bathed in tiny, cream colored flowers that are very reminiscent of the buckwheat family. From a reproductive standpoint, its flowers are quite interesting.
The shrubby tororaro is gynodioecious, which means individual shrubs produce either only female flowers or what is referred to as ‘inconstant male flowers.’ Essentially what this means is that certain individuals will produce some perfect flowers that have functional male and female parts. This reproductive strategy is thought to increase the chances of cross pollination among unrelated individuals when populations are large enough. Following successful pollination, the remaining tepals begin to swell and surround the hard nut at the center, forming a lovely translucent fruit-like structure that entices dispersal by birds. As interesting and effective as this reproductive strategy can be in healthy populations, the shrubby tororaro’s gynodioecious habit starts to break down as its numbers decrease in the wild.
Photo by Jon Sullivan licensed under CC BY-NC 2.0
As New Zealand was colonized, lowland habitats like the grey scrub were among the first to be converted to agriculture and that trend has not stopped. What grey scrub habitat remains today is highly degraded by intense grazing and invasive species. Habitat loss has been disastrous for the shrubby tororaro and its neighbors. Though this shrub was likely never common, today only a few widely scattered populations remain and most of these are located on private property, which make regular monitoring and protection difficult.
Observations made within remnant populations indicate that very little reproduction occurs anymore. Either populations are comprised of entirely female individuals or the few inconstant males that are produced are too widely spaced for pollination to occur. Even when a crop of viable seeds are produced, seedlings rarely find the proper conditions needed to germinate and grow. Invasive grasses and other plants shade them out and invasive insects and rodents consume the few that manage to make it to the seedling stage. Without intervention, this species will likely go extinct in the wild in the coming decades.
Photo by John Pons licensed under CC BY-SA 4.0
Luckily, conservation measures are well underway and they involve cultivation by scientists and gardeners alike. There is a reason this shrub has become very popular among gardeners – it is relatively easy to grow and propagate. From hardwood cuttings taken in winter, the shrubby tororaro will readily root and grow into a clone of the parent plant. Not only has this aided in spreading the plant among gardeners, it has also allowed conservationists to preserve and bolster much of the genetic diversity within remaining wild populations. By cloning, growing, and distributing individuals among various living collections, conservationists have at least safeguarded many of the remaining individuals.
Moreover, cultivation on this scale means dwindling wild populations can be supplemented with unrelated individuals that produce both kinds of flowers. By increasing the numbers within each population, conservationists are also decreasing the distances between female and inconstant male individuals, which means more chances for pollination and seed production. Though by no means out of the proverbial woods yet, the shrubby tororaro’s future in the wild is looking a bit brighter.
This is good news for biodiversity of the region as well. After all, the shrubby tororaro does not exist in a vacuum. Numerous other organisms rely on this shrub for their survival. Birds feed heavily on its fruits and disperse its seeds while the larvae of at least a handful of moths feed on its foliage. In fact, the larvae of a few moths utilize the shrubby tororaro as their sole food source. Without it, these moths would perish as well. Of course, those larvae also serve as food for birds and lizards. Needless to say, saving the shrubby tororaro benefits far more than just the plant itself. Certainly more work is needed to restore shrubby tororaro habitat but in the meantime, cultivation is ensuring this species will persist into the future.
The Ceropegias Welcome a New Member
Photos by David Styles
The genus Ceropegia is home to some of my favorite plants. Not only are they distant cousins of the milkweeds (Asclepias spp.), they sport some of the most interesting floral morphologies whose beauty is only exceeded by their fascinating pollination syndromes. Recently, Ceropegia expert and friend of the podcast Dr. Annemarie Heiduk brought to my attention the recent description of a species named in her honor.
Ceropegia heidukiae hails from KwaZulu-Natal, South Africa, and, at current, is believed to be endemic to a habitat type called the Northern Zululand Mistbelt Grassland. Morphologically, it has been described as an erect perennial herb. Unlike many of its cousins, C. heidukiae does not vine. Instead, it grows a slender stem with opposite, ovate leaves that just barely reaches above the surrounding grasses. By far the most striking feature of this plant are its flowers.
Photos by David Styles.
Ceropegia heidukiae produces elaborate trap flowers at the tips of its slender stems during the month of December (summer in the Southern Hemisphere). Each flower is comprised a greenish-gold, striped tube made of fused petals and topped with a purple, star-like structure with fine hairs. These flowers were the key indication that this species was previously unknown to science. Additionally, a sweet, acidic scent was detected during the relatively short blooming period.
Their beauty aside, the anatomy and scent of these flowers hints at what may very well be a complex and specific pollination syndrome. Indeed, scientists like Dr. Heiduk are revealing amazing chemical trickery within the flowers of this incredible genus, including one species that mimics the smell of dying bees. Who knows what kinds of relationships this new species has evolved in its unique habitat. Only plenty of observation and experimentation will tell and I anxiously await future studies.
A view of the Northern Zululand Mistbelt Grassland where Ceropegia heidukiae was found.
Sadly, C. heidukiae lives in one of South Africa’s most threatened habitat types. South Africa’s Biodiversity Act currently classifies the Northern Zululand Mistbelt Grassland as endangered due to factors like timber plantations and unsustainable grazing. Hopefully with the recognition of unique species like C. heidukiae, more attention can be given to sustainable use of the Northern Zululand Mistbelt Grassland such that both the people and the species that rely on it can continue to do so for generations to come.
Photo Credits: David Styles
Native Plants Make Every Day Earth Day
We get so much joy out of watching people take pictures of our gardens as they walk by our apartment.
Spring is here in the Northern Hemisphere which means gardening season is well underway. Having spent all winter thinking about what kinds of native plants we want to add to our gardens, my partner and I are always very excited to start germinating seeds and propagating plants. Though we always place the plants at the center of our focus, we would be lying if we said a big part of our gardening obsession wasn’t aimed at attracting wildlife to our property.
There is no denying that gardening, especially with native plants, is the best way to benefit local wildlife in your neighborhood. It doesn’t take much to succeed either. Our landlords are amazing people that allow us a certain degree of freedom to do what we wish with the yard, but they still want to ensure that we maintain something akin to a “traditional” suburban landscape. As such, most of our gardening efforts must be crammed into borders and other highly manicured areas surrounding the lawn. Even so, we are constantly amazed by how much life our plants attract.
I really wish we had the foresight to document insect diversity before we began planting so we could do a before and after comparison, but hindsight is always 20/20. From bees to mantis flies and a hefty population of fireflies, we spend hours each week pursuing the garden to see what kinds of interesting critters are hanging around the yard. The amount of insect life in our garden hasn’t gone unnoticed either.
Leafhoppers and treehoppers are among our favorite insects to see in our gardens.
I remember one afternoon a couple years back, our neighbor approached us to ask if we had seen any bees visiting our tomato plants. Our reply was a very enthusiastic “YES” followed by a rundown of our best estimates on how many different bee species we encountered each day. He seemed a bit bummed and replied that he had yet to see a single bee on his plants. This was a teaching moment that we needed to address as tactfully as possible.
You see, this neighbor is obsessed with mowing and spraying. Save for a few irises near his front porch and two raised beds chock full of tomatoes, no other plants beside grass are allowed to establish on his property. Though completely anecdotal, I can’t help but feel his lack of plants translates in a big way to his lack of bees. We mentioned that all of those “weeds” in our yard that he is always “jokingly” giving us a hard time about are the reason that we have so many bees. Tomato flowers are great but they aren’t around all the time and bees need other food to survive. They also need places to reproduce, which means leaving bare patches of soil around the property and allowing plenty of garden debris in the form of stems, twigs, and leaves to remain in place well into summer.
I am not sure we convinced him to completely change his ways with that conversation, but it definitely got him thinking. He asked if next time we have some spare plants if we wouldn’t mind donating a few so that he can plant them near his tomato beds. We enthusiastically agreed. Though a minor victory, we celebrated the fact that our garden had served as a mini catalyst for a tiny change in someone else’s life.
A firefly stopping for a sip of nectar on one of our common milkweeds (Asclepias syriaca).
With Earth Day coming up this week, the internet is full of quick tips on how to make your life more eco-friendly. There are endless articles available to those looking for advice on green living and sustainable gift ideas. I would like to argue that there is no greener gift than the gift of native plants. It doesn’t matter which species or why, just make sure you pick plants that are native to your region. By establishing native plants in your garden or even in pots on your patio or balcony, you are making a great step in celebrating Earth Day every day. Plants are truly the gift that keeps on giving and you can sleep better at night knowing that they are doing so much more than simply beautifying a space. They are providing food, shelter, and a place to breed for the countless organisms that allow ecosystems to function.
And, as we experienced with our neighbor, native plants can offer so many wonderful moments of inspiration and learning. As I discuss in my book, “In Defense of Plants: An Exploration into the Wonder of Plants,” realizing that native plants and the communities they comprise set the foundation for all other life on this planet set me on a path of wonder and discovery that I have never left. Plants changed my life for the better and by surrounding ourselves with them at all times, my partner and I know that we are doing our part to change the lives of the many organisms struggling to survive in this human-dominated world. So, if you want to live every day like it’s Earth Day, brighten up your life with a few native plants and enjoy all of the wonder and beauty they provide.
Some Magnolia Flowers Have Built-In Heaters
Magnolia denudata. Photo by 阿橋 HQ licensed under CC BY-SA 2.0
There are a lot of reasons to like magnolias and floral thermogenesis is one of them. That’s right, the flowers of a surprising amount of magnolia species produce their own heat! Although much more work is needed to understand the mechanisms involved in heat generation in these trees, research suggests that it all centers on pollination.
Magnolias have a deep evolutionary history, having arose on this planet some 95+ million years ago. Earth was a very different place back then. For one, familiar insect pollinators like bees had not evolved yet. As such, the basic anatomy of magnolia flowers was in place long before bees could work as a selective pressure in pollination. What were abundant back then were beetles and it is thought that throughout their history, beetles have served as the dominant pollinators for most species. Indeed, even today, beetles dominate the magnolia pollination scene.
Magnolia sprengeri. Photo by Aleš Smrdel licensed under CC BY-NC 2.0
Beetles are generally not visiting flowers for nectar. They are instead after the protein-rich pollen within each anther. It seems that when the anthers are mature, beetles are very willing to spend time munching away within each flower, however, keeping their attention during the female phase of the flower is a bit trickier. Because there are no rewards for visiting a magnolia flower during its female phase, evolution has provided some species with an interesting trick. This is where heat comes in.
Though it varies from species to species, thermogenic magnolias produce combinations of scented oils that various beetles species find irresistible. That is, if they can pick up the odor against the backdrop of all the other enticing scents a forest has to offer. By observing floral development in species like Magnolia sprengeri, researchers have found that as the flowers heat up, the scented oils produced by the flower begin to volatilize. In doing so, the scent is dispersed over a much greater area than it would be without heat.
Magnolia tamaulipana. Photo by James Gaither licensed under CC BY-NC-ND 2.0
Unlike some other thermogenic plants, heat production in magnolia flowers doesn’t appear to be constant. Instead, flowers experience periodic bursts of heat that can see them reaching temperatures as high as 5°C warmer than ambient temperatures. These peaks in heat production just to happen to coincide with the receptivity of male and female organs. Also, only half of the process is considered an “honest signal” to beetles. During the male phase, the beetles will find plenty of pollen to eat. However, during the female phase, the scent belies the fact that beetles will find no reward at all. This has led to the conclusion that the non-rewarding female phase of the magnolia flower is essentially mimicking the rewarding male phase in order to ensure some cross pollination without wasting any energy on additional rewards.
The timing of heat production also changes depending on the species of beetle and their feeding habits. For species like the aforementioned M. sprengeri, which is pollinated by beetles that are active during the day, heat and scent production only occur when the sun is up. Alternatively, for species like M. tamaulipana whose beetle pollinators are nocturnal, heat and scent production only occur at night. Researchers also think that seasonal climate plays a role as well, suggesting that heat itself may be its own form of pollinator reward in some species. Many of the thermogenic magnolias bloom in the early spring when temperatures are relatively low. It is likely that, aside from pollen, beetles may also be seeking a warm spot to rest.
Personally, I was surprised to learn just how many different magnolias are capable of producing heat in their flowers. When I first learned of this phenomenon, I thought it was unique to M. sprengeri but I was wrong. We still have a lot to learn about this process but research like this just goes to show you that even familiar genera can hold many surprises for those curious enough to seek them out.
Meet the Golden Lotus Banana
While perusing the internet the other day, I scrolled past an image of what looked like the physical manifestation of the sun emoji on my phone. The bright yellow flash was so striking that it caused me to pause and scroll back to the source. I was pleasantly surprised to see that the sun-like object belonged to something botanical. I was even more surprised to find out that it was produced by a unique cousin of the banana called the golden lotus banana (Musella lasiocarpa).
The golden lotus banana is an oddball in many ways. For starters, it has a confusing taxonomic history. For many years, this odd plant has bounced back and forth between what was originally the only two genera in the banana family (Musaceae). Indeed, it has many outward characteristics that could firmly land it in either the genus Musa or the genus Ensete. Still, this plant is strange enough that numerous taxonomists have taken their own stab at narrowing down its correct placement. It wasn’t until DNA analyses revealed it to be so distinct from either of these genera that it warranted its own unique taxonomic placement. Thus, the monotypic genus Musella was born.
The plant itself is well known and widely cultivated throughout its home range in the Yunnan province of China. In fact, the golden lotus banana is so widely cultivated in this region as food for both humans and cattle alike, that experts couldn’t quite figure out if there were any wild populations left. It wasn’t until relatively recently that some wild populations were found. Sadly, these populations are under threat of being completely extirpated as much of the conifer-oak forests it calls home have been highly fragmented and degraded due to human activities. At least its popularity in cultivation means this species is not likely to go completely extinct any time soon.
The golden lotus banana is rather interesting in form. When you look for pictures of this species around the web, you are likely to pull up images of a stubby, nearly leafless stalk tipped with the bright yellow bracts that look like the rays of a cartoonish sun. Apparently, plants can lose many of their leaves in cultivation around the time the inflorescence matures, giving the impression that it never had any to begin with. Of course, the plant does produce typical banana-like leaves for most of the year. As mentioned, the amazing inflorescence is borne at the tip of what looks like a small, woody trunk, but in reality is actually the fused petioles of their leaves. All members of the banana family are, after all, overgrown herbs, not trees.
As is typical with this family, the flowers don’t all ripen at once. Instead, they begin at the base and gradually ripen over time, revealing consecutive whirls of tubular flowers surrounded by bright yellow bracts, though a variant population that produces red bracts was recently described as well. Interestingly, the golden lotus banana differs from its banana cousins in that its flowers are not pollinated by bats or birds. Instead, bees and wasps comprise the bulk of floral visitors, at least among cultivated populations. The first flowers to mature are male flowers that produce a small amount of nectar and copious amounts of pollen. Only the flowers near the base of the inflorescence are female and they produce a lot more nectar than the male flowers.
Research has shown that bees are far more likely to visit female over male flowers and their visits to female flowers last much longer. This is likely due to the differences in nectar production, but the end result is that by encouraging bees to spend less time on male flowers and more time on female flowers, each plant greatly increases the chances that pollen of unrelated individuals will end up on the stigma. After pollination, tiny fruits are formed, however, from what I have read they are largely inedible to humans. Once the fruits ripen and seeds are dispersed, the flowering stalk dies back and is replace by a fresh new growth stalk from the underground rhizome.
The next time you find yourself at a botanical garden with a decent tropical plant collection, keep an eye out for the golden lotus banana. Outside of China, this species has gained some popularity among specialist plant growers and you just might be lucky to stumble across one in the process of blooming.
A Closer Look at Hyacinths
Photo by Radu Chibzii licensed under CC BY-SA 2.0
They say that our sense of smell is very closely tied with the formation of memories. It is around this time of year that I am strongly reminded of the power of that link. All I have to do is catch a whiff of a blooming hyacinth and I am immediately transported back to childhood where spring time gatherings with the family were always accompanied by mass quantities of these colorful bulbs. Indeed, the smell of hyacinths in bloom will forever hold a special place in my mind (and heart).
Because it is spring in my neck of the woods and because my partner recently came home with a wonderful potted hyacinth to add some springy joy our apartment, I decided to take a dive into the origins of these plants. Where do they come from and how do they live in the wild? Certainly they didn’t originate in our gardens.
To start with, there are surprisingly few true hyacinths in this world these days. Whereas many more spring flowering bulbs were once considered members, today the genus Hyacinthus is comprised of only three species, H. litwinovii, H. transcaspicus, and the most famous of them all, H. orientalis. All other “hyacinths” are hyacinths in name only. These plants were once considered members of the lily family (Liliaceae) but more recent genetic work places them in the asparagus family (Asparagaceae).
All three species of hyacinth are native to the eastern Mediterranean region, throughout the Middle East, and well into southwestern Asia. As you might imagine, there is a fair amount of geographical variation across populations of these plants. For instance, H. orientalis itself contains many putative subspecies and varieties. However, their long history of human cultivation has seen them introduced and naturalized over a much wider area of the globe. Generally speaking, these plants tend to prefer cool, higher elevation habitats and loose soils.
As many of you already know, hyacinths are bulbous plants. Throughout most of the year, they lie dormant beneath the soil waiting for warming spring weather to signal that it’s growing time. And grow they do! Because their leaves and inflorescence are already developed within the bulb, hyacinths can rapidly emerge, flower, and leaf out once snow thaws and releases water into the soil. And flower they do! Though selective breeding has resulted in myriad floral colors and strong, pleasant odors, the wild species are nonetheless put on quite a display.
The flowers of wild hyacinths are generally fewer in number and can range in color from almost white or light blue to nearly purple. Their wonderful floral scent is not a human-bred characteristic either, though we have certainly capitalized on it in the horticulture trade. In the wild, these scent compounds call in pollinators who are rewarded with tiny amounts of nectar. It is thought that bees are the primary pollinators of hyacinths both in their native and introduced habitats.
Of course, all of their floral beauty comes down to seed production. Upon ripening, each fruit (capsule) opens to reveal numerous seeds, each with a fleshy attachment called an elaiosome. The elaiosome is very attractive to resident ants that quickly go to work collecting seeds and bringing them back to their colony. However, it isn’t the seed itself the ants are interested in, but rather the elaiosome. Once it is removed and consumed, the seed is discarded, usually in a waste chamber within the colony where it is free to germinate far away from potential seed predators.
Once growth and reproduction are over, hyacinths once again retreat back underground into their bulb phase. Amazingly, these plants have a special adaptation to make sure that their bulbs are tucked safely underground, away from freezing winter temperatures. Throughout the growing season, hyacinths produce specialized roots that are able to contract. As they contract, they literally pull the base of the plant deeper into the soil. This is very advantageous for plants that enjoy growing in loose soils that are prone to freezing. Once underground and away from frost and snow, they lie dormant until spring returns.
I don’t know about you but getting to know how common garden plants like hyacinths make a living in the wild only makes me appreciate them more. I hope this brief introduction will have you looking at the hyacinths in your neighborhood in a whole new light.
When the Going Gets Tough, Desert Mistletoes Cooperate
Sure, parasites can be a drain on their host, but for those parasites whose entire life depends on a living host, it doesn’t pay to kill. Such is the case for the desert mistletoe (Phoradendron californicum). These plants simply can’t live without the water and nutrients they receive from their host trees. But what happens when more than one mistletoe infects a single tree? One would think that supporting multiple mistletoes would be a dangerous drain on the host tree. However, recent research based in the Sonoran Desert suggests that desert mistletoe has a trick up its stems that involves a bit of communication with its neighbors.
Desert mistletoe isn’t completely reliant on its host for all of its nutritional needs. Though lacking leaves, the desert mistletoe is fully capable of photosynthesis via its tangled mass of green stems. Most of what desert mistletoes extract from their host consists of water and other nutrients they can’t acquire themselves. However, desert mistletoes rarely operate alone. Thanks to their nutritious berries and the territorial habits of the birds that disperse them, multiple mistletoe individuals often wind up parasitizing the same tree.
Heavy infestations may sound like a death sentence for the host tree, especially in the harsh Sonoran climate. However, by manipulating the mistletoe loads on various trees and observing how mistletoes and their hosts respond, researchers have discovered that mistletoes can apparently sense their neighbors and alter their behavior accordingly.
During dry periods, trees become stressed for both water and nutrients. For mistletoes growing on a stressed tree, it doesn’t make much sense from an evolutionary standpoint to increase their demand on the host during these times. Instead, mistletoes growing on stressed trees actually increased the amount of photosynthesis they perform without increasing the amount of water they extract from their host. By altering their metabolism in this way, the mistletoes do not add any extra burden to their already stressed host tree but nonetheless maintain their own fitness.
Amazingly, the situation got even more interesting when researchers experimentally removed some mistletoes. Somehow, depending on their position on their host tree, some remaining mistletoes can sense that their competitors had been removed. When this happens, they don’t go into overdrive and start exacting a greater share of resources from their host. Instead, the remaining mistletoe appear to sense that they no longer have to compete as much and adjust their water and nutrient uptake in such a way that actually allows their host to benefit as well.
Certainly these findings generate more questions than they answer. First, how do mistletoes sense their neighbors? Given their direct links with the host vascular tissues, they could be sensing signals from other parasites that way. There is also the potential for airborne signal detection as well. Also, do mistletoes behave differently when growing near related individuals versus strangers? What researchers have ultimately uncovered is a fascinating coevolutionary system in desperate need of more attention.
How Fungus Gnats Maintain Jack-in-the-pulpits
There are a variety of ways that the boundaries between species are maintained in nature. Among plants, some of the best studied examples include geographic distances, differences in flowering phenology, and pollinator specificity. The ability of pollinators to maintain species boundaries is of particular interest to scientists as it provides excellent examples of how multiple species can coexist in a given area without hybridizing. I recent study based out of Japan aimed to investigate pollinator specificity among fungus gnats and five species of Jack-in-the-pulpit (Arisaema spp.) and found that pollinator isolation is indeed a very strong force in maintaining species identity among these aroids, especially in the wake of forest disturbance.
Fungus gnats are the bane of many a houseplant grower. However, in nature, they play many important ecological roles. Pollination is one of the most underappreciated of these roles. Though woefully understudied compared to other pollination systems, scientific appreciation and understanding of fungus gnat pollination is growing. Studying such pollination systems is not an easy task. Fungus gnats are small and their behavior can be very difficult to observe in the wild. Luckily, Jack-in-the-pulpits often hold floral visitors captive for a period of time, allowing more opportunities for data collection.
By studying the number and identity of floral visitors among 5 species of Jack-in-the-pulpit native to Japan, researchers were able to paint a very interesting picture of pollinator specificity. It turns out, there is very little overlap among which fungus gnats visit which Jack-in-the-pulpit species. Though researchers did not analyze what exactly attracts a particular species of fungus gnat to a particular species of Jack-in-the-pulpit, evidence from other systems suggests it has something to do with scent.
Like many of their aroid cousins, Jack-in-the-pulpits produce complex scent cues that can mimicking everything from a potential food source to a nice place to mate and lay eggs. Fooled by these scents, pollinators investigate the blooms, picking up and (hopefully) depositing pollen in the process. One of the great benefits of pollinator specificity is that it greatly increases the chances that pollen will end up on a member of the same species, thus reducing the chances of wasted pollen or hybridization.
Still, this is not to say that fungus gnats are solely responsible for maintaining boundaries among these 5 Jack-in-the-pulpit species. Indeed, geography and flowering time also play a role. Under ideal conditions, each of the 5 Jack-in-the-pulpit species they studied tend to grow in different habitats. Some prefer lowland forests whereas others prefer growing at higher elevations. Similarly, each species tends to flower at different times, which means fungus gnats have few other options but to visit those blooms. However, such barriers quickly break down when these habitats are disturbed.
Forest degradation and logging can suddenly force many plant species with different habitat preferences into close proximity with one another. Moreover, some stressed plants will begin to flower at different times, increasing the overlap between blooming periods and potentially allowing more hybridization to occur if their pollinators begin visiting members of other species. This is where the strength of fungus gnat fidelity comes into play. By examining different Jack-in-the-pulpit species flowering in close proximity to one another, the team was able to show that fungus gnats that prefer or even specialize on one species of Jack-in-the-pulpit are not very likely to visit the inflorescence of a different species. Thanks to these preferences, it appears that, thanks to their fungus gnat partners, these Jack-in-the-pulpit species can continue to maintain species boundaries even in the face of disturbance.
All of this is not to say that disturbance can’t still affect species boundaries among these plants. The researchers were quick to note that forest disturbances affect more than just the plants. When a forest is logged or experiences too much pressure from over-abundant herbivores such as deer, the forest floor dries out a lot quicker. Because fungus gnats require high humidity and soil moisture to survive and reproduce, a drying forest can severely impact fungus gnat diversity. If the number of fungus gnat species declines, there is a strong change that these specific plant-pollinator interactions can begin to break down. It is hard to say what affect this could have on these Jack-in-the-pulpit species but a lack of pollinators is rarely a good thing. Certainly more research is needed.
DK Science: Seed Plants
Most plants grow from seeds. These seed plants fall into two groups, angiosperms and gymnosperms. Angiosperms are the flowering plants. Their seeds develop inside a female reproductive part of the flower, called the ovary, which usually ripens into a protective FRUIT. Gymnosperms (conifers, Ginkgo, and cycads) do not have flowers or ovaries. Their seeds mature inside cones. Seeds may be carried away from the parent plant by wind, water, or animals.
Dandelion seeds have feathery parachutes to help them fly far from their parent plant. A dandelion flower is actually made up of many small flowers, called florets. Each develops a single fruit. The fruits form inside the closed-up seed head, after the yellow petals have withered away. When the weather is dry, the seed head opens, revealing a ball of parachutes. The slightest breeze lifts the parachutes into the air.
INSIDE A SEED
A seed is the first stage in the life cycle of a plant. Protected inside the tough seed coat, or testa, is the baby plant, called an embryo. Food, which fuels germination and growth, is either packed around the embryo or stored in special seed leaves, called cotyledons.
SPREADING WITHOUT SEEDS
Seeds are not the only means of reproduction. Some plants create offshoots of themselves ? in the form of bulbs, tubers, corms, or rhizomes ? that can grow into new plants. This type of reproduction is called vegetative reproduction. As only one parent plant is needed, the offspring is a clone of its parent.
A bulb is an underground bud with swollen leaf bases. Its food store allows flowers and leaves to grow quickly. New bulbs develop around the old one.
A tuber is a swollen stem or root with buds on its surface. When conditions are right, the tuber?s food store allows the buds to grow.
A corm is a swollen underground stem that provides energy for a growing bud. After the food in the old corm is used up, a new corm forms above it.
A rhizome is a horizontal stem that grows underground or on the surface. It divides and produces new buds and shoots along its branches.
GERMINATION OF A RUNNER BEAN
Most seeds require damp, warm conditions in order to sprout. During germination, the seed absorbs water and the embryo starts to use its food store. A young root, or radicle, begins to grow downward. Then a young shoot, or plumule, grows upward. This develops into the stem and produces leaves. The first leaves, called seed leaves or cotyledons, fuel the early growth until the plant?s true leaves appear.
A flower?s ovary usually develops into a fruit to protect the seeds and help disperse them. A fruit may be succulent (fleshy) or dry. Fruit is often tasty and colourful to attract fruit-eating animals. Its seeds can pass through an animal unharmed, falling to the ground in droppings. Seeds may also be dispersed on animals? coats, by the wind, or by the fruit bursting open.
The seeds of dry fruits are dispersed in various ways. Peapods are dry fruits that split and shoot out their seeds by force. The hogweed fruit forms a papery wing around the seed, helping it to float on the breeze. The strawberry is a false fruit, but it is covered by tiny dry fruits, each with a seed.
Fleshy, brightly coloured, and often scented, succulent fruits are designed to attract the animals that eat and disperse them. Fleshy fruits such as apricots and cherries have a woody stone or pip that protects the seed. Called drupes, these fruits form from a single ovary. Many drupes, formed from many ovaries, may cluster to form a compound fruit, such as a raspberry.