HPIPM:Hemp dogbane

Taxonomy

Domain	Eukarya
Kingdom	Plantae
Phylum	Magnoliophyta
Class	Magnoliopsida
Superorder	Asteranae
Order	Gentianales
Family	Apocynaceae
Subfamily	Apocynoideae
Genus	Apocynum

Scientific Name

Apocynum cannabinum

Common Name

hemp dogbane

Hemp dogbane (Apocynum cannabinum)

Compiled by Jane Mangold, Montana State University,

and Marjolein Schat, Montana State University from the following sources:

http://fieldcrop.msu.edu/documents/Controlling%20Hemp%20Dogbane.pdf

http://128.104.239.6/uw_weeds/extension/articles/hempdog.htm

Identification and Life Cycle

Hemp dogbane (Apocrynum cannabinum) is one of several dogbane species (family Apocynaceae) native to North America. Hemp dogbane, also called Indian hemp is a perennial and has an extensive, branched root system with vegetative buds irregularly placed on the lateral roots. The buds can form shoots. Vertical roots may penetrate 8 feet or more but do not have buds. Hemp dogbane stems are smooth and grow 3 to 5 feet tall. They are woody near the base and branch near the top, giving them a "bushy" look. The leaves are smooth, opposite, ovate to lanceolate, and have a very short petiole. Hemp dogbane leaves are bright green during the growing season and turn a yellowish-brown to orangish-yellow in the fall. Hemp dogbane produces clusters of small, greenish-white, bell-shaped flowers at the end of each branch. Each flower may produce two slender, slightly curved, pencil-like pods 3 to 4 inches long. Pods have up to 200 reddish-brown seeds, each with a tuft of silk on one end. Hemp dogbane is similar in appearance to common milkweed, but unlike common milkweed, stems branch near the top. Common milkweed seeds are much wider and flatter than hemp dogbane's spike-shaped seeds.

Habitats

Hemp dogbane occurs most frequently under moist conditions, although can also grow in average, dry to medium wet, well-drained soil. Hemp dogbane is commonly found in gravelly or sandy fields, riparian areas, meadows, along creek beds, irrigation ditches, hillside seeps, and fence lines in cultivated pastures.

Impacts

Hemp dogbane can reduce crop yields and affects the harvestability of several crops. This weed is usually in full bloom during wheat harvest and the milky sap in stems and leaves coats combine parts and grain, causing dirt and chaff to adhere to them. The milky juice in hemp dogbane contains a cardiac glycoside toxin, but plants are very unpalatable to livestock and cases of poisoning are unlikely.

Biology and Ecology

Hemp dogbane is a deep-rooted perennial capable of reproducing by seed or by vegetative buds in the crown region and on the horizontal lateral roots. Seeds are highly viable, and although germination is greater in the light, few seeds on the soil surface produce established seedlings. Most emergence and seedling establishment occur when seeds are half an inch below the surface Plants do not flower the year they start from seed, but flower readily the second season. After two seasons, the primary vertical root can penetrate 14 feet deep and the permanent lateral roots can reach nearly 20 feet long. Hemp dogbane shoots do not emerge until soil temperatures reach 65° F. After emergence, stems grow and develop very rapidly. Plants reach the bud stage 3 to 4 1/2 weeks after emergence. Flowers appear 5 to 11 days after the buds and full bloom occurs 1 to 3 weeks after flowering starts. Seed pods may or may not be formed.

Biological Control

Although several native insects feed on hemp dogbane, specific biological control agents are not available.

Mechanical and Cultural Control

Alfalfa competes well with hemp dogbane. While growing alfalfa may not eradicate hemp dogbane, frequent mowing reduces root reserves, limits lateral root growth, prevents flowering, and avoids spreading root segments on tillage equipment. Winter wheat also competes well with hemp dogbane because it is established in the fall and grows rapidly in the spring before soils are warm enough to stimulate hemp dogbane growth. Winter wheat also provides an excellent opportunity to use mechanical and chemical measures after wheat harvest in late summer or early fall. Soil disturbance readily controls hemp dogbane seedlings. Six to 8 weeks after germination, hemp dogbane is considered "established," as then it can reproduce vegetatively from buds on the root. If seeds have germinated, it is important to till the field before seedlings are well established. Tilling during warm, dry conditions kills root pieces near and on top of the soil surface by desiccation. After tilling hemp dogbane infestations, machinery should be cleaned before moving to non-infested fields.

Chemical Control

A number of chemical control options are available for control of hemp dogbane. For herbicide recommendations for specific grain rotations and weeds in Montana, please see the MSU Herbicide Chooser Tool.

Examples of herbicides that can be used to manage hemp dogbage

Consult herbicide labels for additional rate, application, and safety information. Additional herbicide information can be found at http://www.greenbook.net.

Due to constantly changing labels, laws and regulations, the sponsors of this web site assume no liability for the suggested use of any chemicals noted in the management section. Contact your local pest management personnel for current information on labeled pesticides that can be used for the intended plant disease, insect pest or weed.

References

For more information and images please visit IPM Bugwood. http://www.ipmimages.org/search/action.cfm?q=hemp%20dogbane&Start=1&results=52