Tuesday, August 6, 2019

Black Henbane, Beware!

Jesse Fulbright, MSU Liberty County Extension

Last week I received a phone call here at the Extension office about a weed identification question.  The plant turned out to be black henbane.  As I’m learning about black henbane and recognizing that MSU Extension has a MontGuide publication on it, I thought I would share some information on it this week so if it crops up in other areas, people might recognize it.

Black henbane is a native to Europe and northern Africa.  It has been reported in Montana since 1881 and as of 2010 had been reported in at least 42 counties, being listed as a county noxious weed in multiple counties.  It grows well in a variety of conditions and soils.  The plant itself is an annual or biennial and grows from 1 to 6 feet tall.  The plants I saw north of town were probably in the 4-foot range.  The stems of the mature plant are erect, leafy and thick and branch out widely.  The leaves can be large, up to six inches wide and eight inches long and the foliage is covered in fine, sticky hairs.  The plants, when flowering, exhibit a brownish-yellow flower.  After flowering, two rows of inch long, pineapple-shaped fruit appear.  Each of these fruit capsules contain black, pitted seeds, to the tune of 10,000 to 500,000 seeds per plant. 
Photo courtesy of Utah State University Extension
Photo courtesy of Montana State University Extension
All parts of black henbane are poisonous to humans and livestock.  Livestock will generally avoid it because of its foul odor and bitter taste.  So, what can be done to control it?  However you manage it, the objective should be to prevent seed production.  Black henbane seeds can remain viable in the soil for a period of five years though, so careful attention needs to be paid to keeping plants under control for several consecutive growing seasons. 

The most effect method of control is prevention.  If it does become established, persistent management using a combination of control measures will give the best control.  Cultivation prior to seed production or pulling or digging isolated plants or small infestations prior to seed production can be effective means of controlling the plant.  These methods may have to be repeated over several years to control plants emerging from the existing seed bank. 
There are several herbicides that are listed for providing control of black henbane, including those with the active ingredients dicamba, picloram, metsulfuron or a metsulfuron and chlorsulfuron mixture.  Please remember to read and follow label instructions and continue to monitor the area after applications for any regrowth or new plants coming up.

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