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weed seed pod identification

Early Plants

Early plants can be typically be identified according to their cotyledon, first true leaves, and/or the stem.

Mature Plants

Non-flowering/Basal rosette

Flowering plants

References

Uva R H, Neal J C, DiTomaso J M. 1997. Weeds of the Northeast. Book published by Cornell University, Ithaca NY. The go-to for weed ID in the Northeast; look for a new edition sometime in 2019.

Cornell University’s Turfgrass and Landscape Weed ID app. Identification and control options for weeds common to turf, agriculture, and gardens in New York; uses a very simple decision tree to identify your weed.

Spreading Dogbane

Spreading dogbane in hay field. Photo by Josh Putman of Cornell Cooperative Extension.

Spreading dogbane. Photo by Josh Putman of Cornell Cooperative Extension.

Early July, 2020

Josh Putman is Cornell Cooperative Extension’s SWNY Dairy, Livestock & Field Crops representative. He recently ran across this plant in a hay field that had not been worked for a few years. Spreading dogbane, Apocynum androsaemifolium, is in the same family as milkweeds and swallowworts, and the same genus as hemp dogbane. This perennial plant is found in open, dry areas and in disturbed habitats throughout New York and most of the US and Canada.

Leaves: Leaves are oval, 4-6cm (around two inches long), with smooth edges and pinnate veination. They are arranged opposite each other on the branch.

Mature Plant: 0.6m (2 feet) tall, although some sources say 2-5′, with branching reddish stems. Flowers are found at the ends of branches.

Flowers/Fruit: Flowers are bell-shaped with 5 petals that are fused to form the bell and then curl outwards. Flowers can be white as were seen in western NY, but can also be pink or white with pink striping. Fruit are a long, narrow pod up to 11cm (over 4 inches) long; each flower produces two seed pods. Inside the pods are many small seeds with fluffy tufts, much like milkweed or swallowwort seeds.

Toxicity: Dogbanes are reported to be toxic to livestock, containing a compound that interferes with heart function. This toxicity persists when the plant is dried as well as when fresh. There is no specific information on the toxicity of this species to livestock.

Management: Management information for this species in agricultural settings is sparse; most resources discussed it in the context of a native wildflower/shrub. In blueberry fields, nicosulfuron mixed with surfactant suppressed spreading dogbane (>60%), and dicamba spot sprays were over 80% effective. Glyphosate spot sprays worked better than hand pulling, and wiping with glyphosate was also effective (Wu and Boyd, 2012). In an early experiment from the 1940s, dogbane was partially susceptible to 2,4 D (Egler 1947). In a forest setting, aerial application of glyphosate did not control spreading dogbane (Pitt et al 2000).

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References

University of Maryland Extension Toxic Plant Profile: Milkweed and Dogbane: https://extension.umd.edu/learn/toxic-plant-profile-milkweed-and-dogbane

Ohio State University Perennial and Biennial Weed Guide: Hemp Dogbane. https://www.oardc.ohio-state.edu/weedguide/single_weed.php?id=40

Lin Wu and Nathan S. Boyd. 2012. Management of Spreading Dogbane (Apocynum androsaemifolium) in Wild Blueberry Fields. Weed Technology 26(4)777-782.

Frank E. Egler. 1947. 2,4-D Effects in Connecticut Vegetation, Ecology 29(3)382-386.

Frank E. Egler. 1949. Herbicide Effects in Connecticut Vegetation, Ecology 30( 2) 113-270.

Noxious Weeds overview

Noxious weeds / invasive plants are one of the largest disruptors of ecosystem function. They can colonize a variety of habitats, reproduce rapidly with a variety of mechanisms, and aggressively out-compete native species. A plant is designated noxious in Idaho when it is considered to be injurious to public health, agriculture, recreation, wildlife, or property.

Weeds are typically spread by dispersal of seeds or plant parts in a variety of ways. The wind, water, animals, machinery, and people carry seed and plant parts from one location to another. Many weeds produce abundant seeds with barbs, hooks or other attaching devices that facilitate easy adherence to people, animals or equipment. Because society has become increasingly mobile, weed seeds can and do travel great distances quickly. Weeds usually become established and advance along highways, roads, trails and river corridors. Some noxious weeds, such as purple loosestrife, have been spread through ill-advised horticultural and home garden plantings. Others have been inadvertently introduced through planting of contaminated crop seeds, the feeding of weed seed contaminated forage to livestock, or on vehicles, boats or other machinery.

Weed seed pod identification

in 1934 and has since been found in 19 Montana counties. However, due to a focused early detection and rapid response strategy, dyer’s woad has been eradicated from 13 counties and populations of the plant are now found in only Beaverhead, Flathead, Missoula, Park, Lewis & Clark, and Treasure Counties (Figure 1). This plant is listed as a Priority 1A species on Montana’s noxious weed list, meaning management priorities are early detection and eradication.

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Dyer’s woad management in Montana is coordinated by the Montana Dyer’s Woad Cooperative Project, a collection of county weed districts, state and federal agencies, private landowners, volunteers, and non-governmental organizations, that leads detection and eradication efforts, as well as setting statewide goals for management. To help further the goals of this project, it is crucial to be aware of this plant and its identification, and to contact local weed management entities if suspect plants are found .

Species name: Isatis tinctoria Family: Brassicaceae

Identification: Dyer’s woad plants are usually between one and four feet tall with a long, sturdy taproot up to five feet deep. They have small, yellow flowers with four petals, and flowers are in a flat-topped arrangement (Figure 2). Leaves are bluish-green with a cream-colored midvein. Young rosette leaves have short, soft hairs while stem leaves are hairless and rubbery with bases that clasp the stem (Figure 3, page 2).

FIGURE 1. Dyer’s woad has been reported in 19 Montana counties, but is now present in only six counties due to early detection and eradication efforts. Dark grey indicates the species is currently present in the county, and light grey indicates dyer’s woad was reported in that county and has been eradicated.

The leaves also have a cabbage-like texture. The stem of the plant is often reddish-purple. Seed pods hang in a unique pendulum-like manner. Each seed pod contains one seed and is ½ – ¾ inch long with a teardrop shape. Seed pods start green and turn dark purple to black as they mature (Figure 4, page 2).

Distribution and Habitat: The native range of dyer’s woad is eastern Europe and western Asia. In the United States this species is problematic in states adjacent to Montana and it is listed as a noxious weed in Idaho, Oregon, Utah, Washington, and Wyoming. Dyer’s woad establishes best on rocky, dry soils in disturbed habitats such as roadsides, fence lines, pastures, and railroad rights-of-way. It is also somewhat shade tolerant, meaning it can persist in the understory of forests and other vegetation, though it is usually found in open areas.

Biology, Spread and Impacts: Dyer’s woad usually grows as a biennial, meaning it forms a rosette in the first year and flowers, sets seed, and dies the second year. However, it sometimes displays an annual or perennial life history. This species reproduces only by seeds which are produced from early summer through fall. Each dyer’s woad plant may produce between 350 and 500 seeds. Most seeds fall close to the parent plant, but they can travel longer distances when moved by humans, water, or wildlife. For example, in Montana there is an association between dyer’s woad populations and roads, railroads, and other human travel corridors. Dyer’s woad can be problematic in rangeland, pastures, and cropland, where it reduces the productivity of these systems. This species decreases grazing capacity of rangelands and wildlands for both livestock and wildlife.

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FIGURE 2. Dyer’s woad is from one to four feet tall with small yellow flowers in a flat-topped arrangement. Photo by Noelle Orloff.

FIGURE 3. Dyer’s woad leaves have a distinctive cream-colored midvein. Stem leaves are hairless and rubbery with clasping bases. Photo by Amber Burch.

FIGURE 4. Dyer’s woad has yellow flowers with four petals and pendulum-like, teardrop- shaped seed pods that turn black at maturity. Photo by Amber Burch.

Management: Dyer’s woad management in Montana is currently coordinated by the Montana Dyer’s Woad Cooperative Project, and management priorities are education, prevention, and eradication. Known populations of the plant are monitored by cooperators and detector dogs, and each year plants are hand-pulled or treated with herbicides. Preventing seed production is critical for eradication efforts as dyer’s woad only reproduces by seed. To prevent new infestations, make sure vehicles, equipment, and outdoor gear are clean, and use weed seed-free forage for livestock. Learn to identify this species and report new populations to your local Extension agent or weed district. If you find a new population that is more than half a mile from a known population, there is a $50 bounty available. Small patches of dyer’s woad can be controlled by handpulling or cutting below the root crown with a hoe or shovel. If plants have seed pods, bag plants securely in garbage bags and dispose of them in the garbage.

Additional resources
Acknowledgements

The authors would like to thank Amber Burch, Monica Pokorny, and Tom Monaco for reviewing this publication.

If you are suspicious that you may have found dyer’s woad, contact Amber Burch of the Montana Dyer’s Woad Task Force at 406-925-1346.