Montana Field Guide

PLANTS: An annual or biennial forb with erect, usually branched, stems that grow from a large white, branched taproot. Plants are typically tall, 25-100 cm. Plants have sticky (viscid) and long, soft, crooked, but unmatted (villous) hairs, especially on the stems and veins. Plants are poisonous and have an unpleasant or offensive odor (malodorous). Sources: Lesica et al. 2022; Pokorny et al. 2026

LEAVES: Foliage has a wrinkled appearance. Leaves are gray-green with a whitish mid-rib (vein), and arranged in a basal rosette and alternately on the stem. Basal leaves are lobed and covered with fine hairs. Stem leaves have winged petioles that clasp, but become sessile upwards. Blades are ovate or narrowly triangular in outline and large, 3-30 cm long, with acute tips. Leaf margins are shallowly lobed (pinnate) to coarsely toothed (dentate). Lower surface is often glandular-hairy. Sources: Lesica et al. 2022; Pokorny et al. 2026

INFLORESCENCE: A branched, leafy-bracteate raceme with large, yellowish, purple-veined, and slightly irregular flowers. Calyx: bell-shaped (campanulate) with 5 united green sepals; usually 10-12 mm long, but greatly expanded in fruit. Corolla: 5 united petals, pale to greenish yellow with purple throat and veins; funnelform, consisting of a 15-30mm tube and 20-25 mm limb where the 5 lobes are unequal. Fruit: A globose capsule, 1-2 cm long, and enclosed by the rein, glandular calyx. Sources: Lesica et al. 2022; Pokorny et al. 2026

Flowers are produced from June to September, with peak flowering occurring in July (Pokorny et al. 2026; Vincent in Flora of North America (FNA) 2023).

Black Henbane is a sticky and malodorous plant at all stages of its life cycle, especially when the leaves are crushed (Pokorny et al. 2026). Distinctive features of this plant are the erect stems with alternate, lobed, and slightly wrinkled leaves, that terminate into a raceme of large, dull yellowish flowers with purple throats and veins.

The genus Hyoscyamus is from the Greek word, hyoskyamos, where hys means 'sow' or 'pig' and kyamos refers to 'bean pod' (Giblin et al. [eds.] 2018; Herbal Reality 2026). This gave rise to the common name of 'hog bean' because pigs are apparently the only livestock that have some protections against its toxic properties (Herbal Reality 2026).

Henbane means death-death because it is derived from hen- which refers to 'death' and bane which refers to 'murder, death, or 'thing that causes death' (Wikipedia 2026; Liberman and Mitchell 2008). From an etymological perspective, the common name of 'henbane' is a tautological compound, because hen- and bane have the same historical meaning yet each provides no additional information.

In Montana, Black Henbane grows where land has been disturbed, such as along roadsides and fence lines, and in fields, irrigation ditches, and pastures within the plains and valleys zones (Lesica at al. 2022; Pokorny et al. 2026). Black Henbane grows in sandy and well-drained loam soils of moderate nutrient levels or high nitrogen places. Plants especially grow well where soils are moist, such as riparian areas, but not in water-logged places (Pokorny et al. 2026).

SOIL ECOLOGY
Plant growth is nurtured by increasing levels of soil nitrogen (Pokorny 2026).

MEDICINAL PROPERTIES [Adapted from Herbal Reality 2026; USFS 2026; Wikipedia 2026]
Since at least the 13th century and into the 21st century Black Henbane continues to be studied for its toxic compounds and medicinal properties. In ancient Greece, henbane was used in combination with other plants to create "magic brews" with properties that included visual hallucinations to commune with the divine. Arrows and javelins were poisoned with a decoction made with henbane. It was used as a sedating and calming agent, though also known for its power to cause death. In the Middle Ages, henbane was a major ingredient in an ointment that was said to give the hallucinatory sensation of flying, and became known as "Witches Herb". Through illustrations, this gave rise to the archetype that witches fly on broomsticks.

Henbane is a practitioner-only herb used for anti-spasmodic conditions (Herbal Reality 2026). Black Henbane was once listed in the United States Dispensary in 1918 because doctors used the plant. Today, North American Herbalists are not known to use the plant because many other, safe anti-spasm herbs are available. Within henbane, tropane alkaloids reduce the activity of the parasympathetic portion of the autonomic nervous system which activates and monitors involuntary activities - like heart rate, breathing, blood pressure, digestion, and urination. It is used in medicine for the relief of spasms, especially in the digestive and urinary tracts, and also for bronchial spasms within the respiratory tract. It has been used to address excessive salivation and tremors, such as found in Parkinson's disease. High doses of henbane can cause delirium, seizures, an irregular heartbeat, and a painful death.

Useful Links:
Herbal Reality
Henriette's Herbal Homepage

PLANT PHYSIOLOGY & CHEMISTRY
Black Henbane is classified as a narcotic and poisonous plant (Giblin et al. [eds.] 2018). Plants contain alkaloids, including hyoscyamine, scopolamine, atropine, and others. These alkaloids create a bad odor that have been described as similar to rotting flesh, dead fish, or moldy potatoes (Herbal Reality 2026).

Black Henbane reproduces by seed.

FLOWERS
Stamens: 7-8mm long of which filaments are about 5-7mm and anthers 2.1mm. Ovary: 2-3 by 2-25mm. Style: 10-12 mm long.

FRUITS
After flowering, the raceme produces two rows of pineapple-shaped fruits (Pokorny et al. 2026). Each fruit is a globose capsule, 1-2 cm long. Capsules can persist through the winter.
Seeds: black, pitted.

LIFE CYCLE [Adapted from Pokorny et al. 2026]
In late May, seeds germinate and develop into a basal rosette of leaves. Plants grow up to six feet tall. Flowers are produced from June to September, with peak flowering occurring in July. Black Henbane plants produce 10,000 to 500,000 seeds per year. Field observations suggest that seeds may remain viable in the soil for five years.

COUNTY & STATE DESIGNATIONS
Under the North American Weed Seed Free Forage program, Black Henbane is classified as a 'weed' and prohibited from being transported in forage across state boundaries (Pokorny 2026). As of 2024, Black Henbane is listed as County Noxious in 15 counties: Beaverhead, Big Horn, Broadwater, Deer Lodge, Glacier, Golden Valley, Lewis & Clark, Meagher, Musselshell, Powder River, Powell, Ravalli, Rosebud, Stillwater, and Sweet Grass.

INTEGRATED VEGETATION MANAGEMENT
An integrated vegetative management approach provides the best long-term control, and requires that land-use objectives and a desired plant community be identified (Shelly et al. in Sheley and Petroff 1999). Once identified an integrated weed management strategy that promotes a weed-resistant plant community and serves other land-use objectives such as livestock forage, wildlife habitat, or recreation can be developed.

Black Henbane is an invasive, narcotic, and poisonous plant. Its establishment, spread, and growth are associated with disturbed soils, especially those that are moist or of higher nitrogen levels.

PREVENTION
Focus on preventing establishment, spread, and seed production, using a variety of practices:
* Learn to identify Black Henbane at various stages of development.
* Minimize soil disturbance and maintain competitive desirable plants.
* Contain current infestations.
* Where maintaining competitive vegetation is not possible – like in horse pastures - pull existing Black Henbane plant to prevent their spread and establishment. Wear gloves and protective clothing. Dispose into a plastic bag, tie, and let bake in the sun for 3 weeks prior to dumping into the landfill.
* Report new infestations to the landowner, land manager, or weed district.
* Always sow certified weed-free seeds. Beware of soil, forage, and crop seed that could be contaminated with Black Henbane and other invasive plants. Dried plant material retains its toxic properties and should be not baled.

GRAZING
Livestock grazing is NOT an option because the plants are poisonous to livestock – horses, cattle, goats, and sheep – but apparently not to pigs (Herbal Reality 2026). The toxins include hyoscyamine and other toxic alkaloids. Livestock usually avoid Black Henbane because it has a foul smell (Whitson et al. 1996). Occasional reports of livestock poisoning have been reported (Whitson et al. 1996).

A livestock grazing management plan that does not excessively graze the rangeland creates resiliency to help prevent Black Henbane from establishing.

PHYSICAL and CULTURAL CONTROLS
Hand-pulling is effective for isolated or small infestations where the taproot is also removed. Pull before seed-set. Wear gloves and protective clothing to prevent skin irritations. Plants are tough with thick stems and roots. Therefore, pull plants when soils are moist, and when plants are younger (smaller). Pull throughout the season to ensure that no seeds are produced. Pulling and digging may require several consecutive years of effort where a seed bank has accumulated. Dispose of plants into a sealed plastic bag, tie, and bake in the sun for 3 weeks before moving to the landfill.

Burning kill seeds and prevents spread. Plants can also be burned, though protective clothing and face mask should be used.


Mowing should be done before seed set. Repeated mowing can be effective to prevent seed production.

Repeated Tilling can prevent Black henbane from establishing.

CHEMICAL
Herbicides can be effective, especially when properly integrated with intensive pasture management. Effectiveness and impact to non-target species will depend upon many factors, including herbicide type and concentration, application time and method, environmental constraints, land use practices, and local regulations. Strict adherence to application requirements defined on the herbicide label will reduce risks to human and environmental health. Consult your County Extension Agent and/or Weed District for information on herbicidal control. Chemical information is also available at Greenbook.

Herbicides should be applied with a non-ionic surfactant at the rosette stage and prior to flowering to prevent seed production (Pokorny et al. 2026). The following herbicides (Trade Names) have been found effective in killing Black Henbane: Aminopyralid (Milestone); Dicamba (Vanquish, Clarity); Picloram (Tordon); Metsulfuron (Escort XP); Metsulfuron = chlorsulfuron (Cimarron Plus); and Aminopyralid + metsulfuron (Chapparal). For details on application rates and timing see Pokorny et a. 2026 or talk with your local weed district.

BIOLOGICAL CONTROL
No biological control has been identified for controlling Black Henbane (Pokorny et al. 2026).

Useful Links:
Central and Eastern Montana Invasive Species Team
Montana Invasive Species website
Montana Biological Weed Control Coordination Project
Montana Department of Agriculture - Noxious Weeds
Montana Weed Control Association
Montana Weed Control Association Contacts Webpage
Montana Fish, Wildlife, and Parks - Noxious Weeds
Montana State University Integrated Pest Management Extension
Weed Publications at Montana State University Extension - MontGuides

Black Henbane is an invasive, non-native plant that can form dense stands if not controlled. Plants are robust and can outcompete other desirable vegetation, decrease forage production, and reduce plant diversity whether in managed or natural areas. Their high levels of alkaloids, unpleasant odor, and bitter taste makes all parts of the plant poisonous to humans and livestock. Plants should not be ingested. Their aggressive growth results in the displacement of plants that are more palatable, native, and/or desired. In addition, they are considered a contaminant if baled into hay because the dried plant retains its toxicity.