Field Guide     Weed Management     Hemp Dogbane

Hemp Dogbane (Apocynum cannabinum)

Crop Impacts: Corn and soybeans

Hemp Dogbane 1

About Hemp Dogbane:

Hemp Dogbane is an aggressive, annual weed that is native to North America and starts to grow in late spring or early summer. Once this plant is introduced into a new area, establishment happens quite quickly. Hemp Dogbane has been shown to reduce 8 to 10% of corn yield and 40% of soybeans yield. This plant is also poisonous when ingested. It takes about 6 to 12 hours after an animal has ingested the plant to die. Leaves of this plant are poisonous at all times even when it is dried. Typically the lethal does for animals it about .5gm/kg of their body weight.

Family: Dogbane family (Apocynaceae)

Hemp Dogbane 2 Hemp Dogbane 3

Hemp Dogbane Scouting and Prevention:

The Hemp Dogbane can stand at about 1 to 2m tall. The smooth-edged leaves turn from green to yellow in the fall and produce little hairs that sit on the lower surface of the leaves. The leaves on the Hemp Dogbane also grow opposite of one another of the stem that is reddish in colour and contains a milky sap. Hemp Dogbane has greenish-white flowers that eventually turn into two long pods containing several seeds that have white, silky tufts at their ends.

Common locations

  • - Gravelly fields
  • - Sandy fields
  • - Corn fields
  • - Soybeans fields

Prevention

The best solution is protection. Making sure that your equipment is clean of roots and seeds after leaving an infested area is a simple way to reduce the weed spread. Buying clean weed-free seeds is another crucial step that is strongly recommended.

Hemp Dogbane Control:

Cultural Control

Taking control of Hemp Dogbane in a field is very difficult; however, alfalfa and winter wheat are good competitors for it. Growing alfalfa will not completely get rid of Hemp Dogbane; however, it will reduce its root reserves and lateral root growth and will prevent is from flowering by the frequent mowing of alfalfa. Winter wheat can also weaken Hemp Dogbane due to the fact that is establishes during the fall and rapidly grows in the spring before the soil temperature is warm enough to stimulate growth for Hemp Dogbane. Soil disturbance is also another great way to keep Hemp Dogbane under control. Hemp Dogbane is considered established 6 to 8 weeks after germination, which will happen when the temperature is about 20 to 30˚C. Thus, it is important to till the field before the seeds have time to establish in warm, dry conditions to kill the roots near the top of the soil.

Chemical Control

The most aggressive way to deal with Hemp Dogbane is with herbicides. There are many herbicides that can control Hemp Dogbane when they are still seedlings, but few are as effective once the plant has been established. Fall application of 2.4-D is typically the most effective termination method. Herbicide called Banvel/Clarity (dicamba) is good to use in corn fields. That being said, it is important to know that dicamba cannot be applied as pre-harvest treatment on corn fields. Beacon (primisufuron) is another herbicide that suppresses Hemp Dogbane and works well if 2,4-D is spread afterward. Roundup (glyphosate) sprayed on the late buds to early flowering stages of Hemp Dogbane at 3 to 4gt/acre significantly reduces the infestation and can be applied to soybeans pre-harvest.

Latin / Alternative Hemp Dogbane names:

  • - Apocynum cannabinum
  • - American hemp
  • - Bowmans root
  • - Chactaw root
  • - Dogbane
  • - Indian hemp
  • - Rheumatism weed
  • - Snakes milk

Additional Hemp Dogbane Resources

http://www.ars.usda.gov/Research/docs.htm?docid=9938

http://www.oardc.ohio-state.edu/weedguide/singlerecord.asp?id=560

http://fyi.uwex.edu/weedsci/1994/11/04/hemp-dogbane/

http://www.msuweeds.com/worst-weeds/hemp-dogbane/