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In the Industrial Hemp Regulations, industrial hemp includes Cannabis plants and plant parts, of any variety, that contains 0.3% tetrahydrocannabinol (THC) or less in the leaves and flowering heads.
Industrial hemp also includes the derivatives of industrial hemp plants and plant parts. These do not include the flowering parts or the leaves.
Examples of derivatives that are considered industrial hemp include: hemp seed oil (oil derived from seed or grain) and hemp flour.
Industrial hemp does not include:
Non-viable Cannabis seeds, except for their derivatives. While the derivatives of non-viable Cannabis seeds are considered to be industrial hemp, the non-viable seeds themselves are not industrial hemp; Mature Cannabis stalks, when those stalks are stripped of their leaves, flowers, seeds, and branches; Fiber derived from such mature Cannabis stalks. Most activities with non-viable cannabis seeds, with bare mature cannabis stalks (without leaves, flowers, seeds, and branches), and with fiber derived from bare mature cannabis stalks, are not controlled under the CDSA. As such, they do not require authorization.
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How To Prune Your Cannabis Plants
Many plants on Earth benefit from being pruned from time to time. The cannabis plant is certainly one of those plants. Properly pruning cannabis plants can help the plant reach its full potential by increasing the yield and quality of harvests. Improper pruning or too much pruning can be detrimental to a cannabis plant, and in some cases, can even kill the cannabis plant.
What are the major benefits of pruning marijuana plants? When does a cannabis cultivator know that it is time to start pruning your plants? What are the best pruning methods if pruning is appropriate? What are some common pitfalls when it comes to cannabis pruning? We will explore each of those questions in detail below.
Why Prune Cannabis Plants?
The two most important reasons for pruning cannabis plants are to increase airflow and increase light transparency. Some cannabis strains are notorious for producing an abundance of huge fan leaves, while other cannabis strains may not produce as many leaves. Fan leaves typically do not have trichomes on them, whereas sugar leaves are heavily coated with trichomes.
For strains that do not produce a lot of fan leaves, pruning branches and leaves will not be as important. However, for strains that produce a lot of leaf growth, pruning is a must to keep the plant healthy and happy. If a cannabis plant has too many fan leaves, essentially laying on top of each other, airflow is impeded and moisture can be locked inside the inner region of the plant, creating a breeding ground for various plant diseases such as powdery mildew.
Light transparency is really important for a cannabis plant’s growth. Not only do the inner and lower parts of the plant need access to direct light to ensure uniform growth, light can also help cannabis plants fight off disease. Most importantly, light transparency increases the number of buds on a cannabis plant and makes the bud sites more uniform in size.
Sometimes cannabis pruning is needed because of garden space issues. If you grow cannabis in a confined space, leaves can become pressed up against walls, creating the same issues as leaves laying on top of each other. For growers who are trying to be discreet, plants may need to be a certain size so that they don’t draw unwanted attention. In those situations, ongoing pruning may be necessary as the plant grows.
When To Prune Cannabis Plants
Knowing when to prune your plants is very important. Cannabis cultivators should avoid pruning cannabis plants leading up to the flower stage and definitely during the flowering stage. The best time to prune cannabis plants is early in the cultivation process, preferably in the first week or two of the vegetative growth stage.
A cannabis plant starts to produce leaves throughout the vegetative stage, however, it stops producing new leaves once the plant goes into the flower stage. Fan leaves will get larger, however, they will not regenerate. Any leaf that is cut off during the flower stage will not come back, so always keep that in mind. Once it’s gone, it’s gone.
As legendary cultivation expert Kyle Kushman points out, fan leaves are like the solar collectors for the cannabis plant, so cultivators want to be very mindful when removing them. Fan leaves play a big role in collecting sunlight for the photosynthesis process. They also directly contribute to the size and overall health of the cannabis plant. The only time that leaves should be removed in the flower phase is if the leaf is showing signs of disease or pest infestation, or if it’s required due to space limitations.
How To Prune A Cannabis Plant
The best approach to pruning a cannabis plant is a strategy that Kyle Kushman describes as “selective leaf pruning.” The ultimate goal when it comes to pruning is to increase light transparency toward the middle of the cannabis plant and airflow throughout the plant. With that in mind, start the pruning process toward the middle of the plant.
Watch air from a fan or wind go across the plant to identify areas where big clumps of leaves are catching the moving air. If the leaves are moving in a similar fashion to the sail on a boat, then some of the fan leaves probably need to be removed in order to increase airflow to areas that are most susceptible to moisture-related issues.
Also, removing the lowest branches helps fight off pests that might reside in the grow medium being used. The lowest branches typically do not yield desirable cannabis, and removing them helps the plant focus its energy on the upper branches, where the bulk of the quality flowers are produced.
Big fan leaves that are pointing toward the middle of the plant should also be removed to boost light transparency. You want to be mindful of future growth, and ultimately, you want to have branches growing laterally versus horizontally to ensure that as much of the plant as possible is getting direct light. If you combine proper pruning techniques with strategic bracing of branches, the end result is a plant that is wide and packed with buds. Be careful when bracing — branches break, and when they break, they usually die.
Cannabis Pruning Tips & Common Mistakes
It takes time and practice to become a master cannabis plant pruner. Novice cannabis cultivators will likely commit a mistake or two that they will hopefully learn from. The most common mistake of pruning a cannabis plant during the flower phase was already covered, however, there are other common mistakes that should be avoided.
Arguably the most common mistake that newbie cannabis cultivators make is stripping too many of the fan leaves from the plant. Cultivators should not prune more than 1/3 of the fan leaves on a cannabis plant in any given pruning session. Also, pruning sessions should be limited. Ideally, cultivators should only have to do bulk pruning once or twice on a cannabis plant.
Pruning limitations should not be confused with picking off dead leaves here and there. Always remove the leaves that are dead or showing signs of disease and/or pest infestation. If you have already stripped a cannabis plant too aggressively, yet it’s still in the vegetative stage, you can help address the issue by letting the plant remain in the vegetative stage longer than originally planned. Obviously, that is not something that is an option for everyone and it is situation dependent.
Weed biology often informs management decisions. Weed management practices that disrupt the weed’s life cycle by targeting weak points will result in better weed control. The biology of kochia is particularly problematic because of its ability to emerge in early-spring, grow rapidly, and tolerate heat, drought, and saline soil conditions. The spread of kochia, including widespread herbicide-resistant biotypes, is facilitated by obligate outcrossing and tumbleweed physical seed dispersal mechanisms. Small emerging kochia seedlings have leaves that are densely covered in small, fine, white hairs in what is commonly referred to as the button stage. Herbicide applications during button stage are discouraged (as often stated on herbicide label) as leaf hairs can reduce foliar absorption of herbicides by suspending droplets above the leaf cuticle on the leaf hairs.
Around two weeks after seedling emergence, leaf hair density decreases as leaves grow. After the button stage, kochia leaves maintain fine leaf hairs on the bottom of the leaf, while leaf tops are smooth. It is common to see high seedling densities, especially around the location where the parent plant was growing before detaching from the soil when mature. This is often referred to as a “kochia mat.”
Kochia leaves are alternate with simple blades that are highly pubescent and arise on erect, highly branched stems. Kochia flowers are inconspicuous without petals, and on a given flower the stigmas emerge prior to anther development which facilitates cross pollination between plants. Flowers develop in clusters in the axils of upper leaves and in terminal spikes. Seeds are around 1.5 mm long and develop in star shaped fruit that are brown and flattened. Kochia has a shallow taproot which can be easily pulled or hoed out at early growth stages. Once fully matured, an abscission layer near the soil surface allows for whole plants to detach and bounce across the landscape dropping seed in a wind-driven process known as ‘Tumble mechanism’.
Kochia is a summer annual broadleaf weed species native to Eurasia and was introduced to the Americas as an ornamental in the mid to late 1800s by European immigrants. Ornamental kochia escaped cultivation and formed naturalized populations that now occur throughout most of the continent, especially in arid and semiarid environments. The ability to grow in dry, saline soils has led to adaptation and widespread distribution of kochia in the arid west and semi-arid Great Plains.
Kochia growth and architecture is highly influenced by inter and intraspecific competition. When growing with competing vegetation, growth is more erect, single stemmed and taller; when growing in the absence of competing vegetation, it is more bushy and multi-branched with a larger plant diameter. In moderately dense kochia stands that promote erect, taller primary axis growth, plants can get over six feet tall. While in low competition environments high light intensity suppresses apical dominance and lateral growth resulting in plants typically around three feet tall with oval growth forms and a diameter similar to its height.
Where is kochia a problem?
Kochia is common in rangeland, pastures, and crop production systems where it has adapted and thrives in semiarid to arid regions of North America. It is also commonly found along roadsides, ditch banks, railroad tracks, and in other disturbed sites as a ruderal species. Kochia is competitive in cropping systems due to its ability to germinate and emerge early at low soil temperatures, grow rapidly, and tolerate heat, drought, and saline soil conditions. In areas at high risk of saline seep development, dense kochia patches are a common indicator of increasing soil salinity in crop fields. With further herbicide-resistance development, kochia is becoming more problematic in chemical-fallow fields.
What is the emergence pattern of kochia?
Kochia has a wide window of emergence due to the unique ability to germinate at low temperatures as early as January and continue to emerge throughout the summer into July. High seedling emergence in early spring and continued emergence into mid or late-summer means kochia must be managed from early spring through late summer. Kochia seed does not generally exhibit innate dormancy so mature seeds are readily germinable and will germinate rapidly under favorable conditions, prolonging the emergence period.
What is the lifecycle of a kochia plant like?
Kochia can germinate in low temperatures early in the spring with emergence extending into July. Kochia will grow vegetative throughout the spring and summer before flowering; it can produce copious amounts of pollen. In the fall, fully senesced mature kochia plants will detach at the soil surface and tumble across the landscape, dropping seeds with each impact, in a wind-driven process that spreads seeds long distances.
How does kochia spread?
Kochia physically spreads seeds via a tumbling mechanism where the senesced (mature) plant’s stem breaks at the soil surface, which allows the plant to roll across the landscape in the fall dropping seed along the way in a wind-driven process. Studies have shown that kochia tumbleweeds can move up to 3,280 feet (plants were stopped at fence line at this distance), and pollen from kochia can move up to 315 feet, allowing for the rapid physical spread and genetic exchange between individuals.
How many seeds can kochia produce and how long can those seeds survive?
Kochia is a prolific seed producer. Seed production per plant can vary widely depending on stand density and the extent of intra- and interspecific competition. Seed production of field-grown kochia has been shown to range from 2,000 to 30,000 seeds per plant, with an average of around 14,000 seeds per plant. More recent evaluations of seed production from kochia growing in sugarbeets have shown that individual kochia plants can produce over 100,000 seeds per plant. Kochia seed is relatively short lived in the soil with a mean seed bank longevity of 1-2 years. Kochia seedlings typically cannot emerge from greater than two inches deep in the soil.
What other biological weaknesses does kochia have that can be targeted with management techniques?
The weakest points in a kochia plant’s life cycle are the seed and seedling growth stage. The seeds are short-lived and germinate rapidly under favorable conditions in the top two inches of the soil. Management efforts should focus on suppressing weed seed germination and seedling emergence through strategic tillage, preemergence (PRE) herbicides, and competitive crops. The wind-driven tumbleweed dispersal mechanism allows the use of fence lines or physical barriers to minimize the movement of kochia between fields, although an extensive build up of kochia tumbleweeds on fences can occur. Planting a few rows of a stiff stemmed crop like corn or sorghum along field borders of the prevailing winds can help prevent kochia tumbleweeds from dispersing their seeds in the field. An unharvested strip of small grains can be left as a kochia barrier, too, though it is not as effective as corn.
This graph shows documented cases of herbicide-resistant kochia in the US that have been reported to the International Herbicide-Resistant Weed Database, www.weedscience.org. Both resistance to a single herbicide group, as well as resistance to multiple herbicide groups, are displayed. Contact your local extension office for details about resistance in your area and management options.
*Herbicide names listed are representative products that contain specific active ingredients. Last updated on: 8-10-2020
Integrated Weed Management Strategies
Cultural Tactics: Focusing on control of emerged seedlings prior to planting through strategic shallow-tillage (e.g. Undercutter/V-blade) to remove germinated seedlings where acceptable can help manage early emerging kochia. Establishing competitive crops using optimum planting dates, row spacing, seeding rates, and competitive varieties that close their canopy faster can help crops to compete with kochia, especially during early critical weed free periods. Establishing competitive crops such as winter wheat has been shown to reduce kochia biomass in field studies by over 99% compared to treatments without wheat. Mowing kochia closer to flowering has been shown to reduce seed densities the following year by 98% and reduce biomass by 33% compared to a non-mowed control in a surface mining reclamation project. Chemical fallow is commonly used in the high plains, however the development of herbicide-resistance to commonly used fallow herbicides allows for maximum kochia growth and seed production in the absence of plant competition. Kochia that are able to grow in chemical fallow can rapidly spread a resistance trait through both seed and pollen dispersal. Resistance to glyphosate (RoundUp) is commonly seen in chemical fallow with the meandering trails of kochia throughout the field
Cover Crops: Fall-sown cover crops can compete with both late-fall and early-spring emerging kochia to help minimize kochia growth and biomass production. Fall-sown triticale has been shown to reduce kochia densities by 78 to 94% and biomass by 98% compared with kochia in chemical fallow. Because kochia and spring-planted cover crops both germinate at the same time in early spring, spring-planted cover crops are not effective at reducing kochia densities or biomass. This emphasizes the value of fall-sown cover crops for kochia suppression. Fall-sown cover crops that produce the most biomass are most effective at suppressing kochia. However, evaluation of cover crops for weed suppression in semiarid environments has concluded that growing cover crops instead of fallowing is not beneficial if there is insufficient moisture for the subsequent cash crop at planting. However, if adequate precipitation or irrigation is present, cover crops can reduce soil moisture evaporation and help conserve moisture for crop establishment.
Mechanical: Early spring tillage prior to crop planting provides good control of early emerging seedlings. Less intensive, shallower ridge tillage has been shown to increase kochia densities up to 50 fold, which can be used to promote spring germination and emergence for subsequent control. If herbicide resistance becomes a major issue in a given field, strategic deep tillage (e.g. moldboard plowing) (> every five years) can help reduce population numbers by inverting the soil and burying kochia to a depth where it is no longer able to germinate or remain viable (since average viability is two years). Studies have shown that preplant plowing can reduce kochia densities by 4.5 and 45 fold compared to disk or ridge tillage, respectively, showing the impact of burying kochia more than two inches deep. Mowing kochia before or during flowering is an effective strategy to reduce seed production. However, regrowth can occur which may require repeated mowing depending on time of year.
Chemical: Kochia has evolved resistance to several different herbicide modes of action (MOAs) (resistance to multiple MOAs within populations has been documented) which limits the use of those herbicide groups on certain populations. It is necessary to know if resistance to certain MOAs is present in a given population to formulate a successful herbicide program.
Chemical-fallow control of kochia is often where herbicide resistance, especially to glyphosate, is observed. Herbicide resistant populations are readily visible, with meandering trails of individuals (resistant progeny seed dropped as the parent plant tumbles across a field in the fall) surviving chemical applications in fallow fields. With increased glyphosate-resistant kochia in fallow, alternative auxin herbicides such as dicamba (Clarity) or fluroxypyr (Starane Ultra) are commonly used. However, resistance is continuing to evolve to these herbicides as selection pressure switches from glyphosate to auxin herbicides.
Whether entering a fallow or cropping rotation, starting clean by removing weeds and planting into weed-free fields is critical to minimize weed competition for resources. Burndown products that contain glyphosate (RoundUp), glufosinate (Liberty), or paraquat (Gramoxone) are effective at controlling smaller emerged kochia prior to planting or entering a fallow period. Diversifying weed management strategies for kochia are essential to preserve and extend the longevity of currently effective chemical control methods.
Within crops there are many PRE and POST herbicide options available for kochia control, however, herbicide resistance present at the field level will dictate efficacy of these products. Herbicide applications to kochia should be avoided during the early button stage due to dense leaf hairs that can reduce foliar adsorption. Reducing seed germination with PRE herbicides, as well as targeting smaller, more vulnerable kochia seedlings, should be the focus of chemical control programs.
Herbicide resistance to group 2 (ALS), group 9 (EPSPS-inhibitor on the plot), group 5 (PSII), and group 4 (Synthetic Auxins) has resulted in a need to start clean with PRE herbicides as the foundation for kochia control programs. Examples include products that contain pyroxasulfone (Zidua) or s-metolachlor (Dual II Magnum), sulfentrazone (Spartan), HPPD-inhibitors (eg isoxaflutole or mesotrione), metribuzin (Sencor), saflufenacil (Sharpen), dicamba (PRE), and atrazine (depending on if triazine resistance is present) or combinations of above. Postemergence herbicides that contain glyphosate (RoundUp), glufosinate (Liberty), dicamba, fluroxypyr (Starane Ultra), mesotrione (Callisto), tembotrione (Laudis), bromoxynil (Buctril), pyrasulfotole, atrazine, or combinations of the above, are effective at controlling susceptible kochia populations in various crops or fallow. Diversifying chemical control tactics and targeting smaller, more vulnerable growth stages can help reduce herbicide resistance development in kochia.
Biological: There are currently no biological control agents for kochia. Kochia is so ubiquitous that biological control is not a realistic option.