- Growing form: Usually biennial (occasionally annual) herb.
- Height: 15–100 cm (6–40 in.). Stem sparsely branched, densely leaved, sticky, densely hairy.
- Flower: Slightly zygomorphic. Corolla brownish yellow, usually purple-veined, fused, widely funnel-shaped, short-tubed, 5-lobed, 20–30 mm (0.8–1.2 in.) wide. Calyx fused, campanulate (bell-shaped), 5-lobed, enlarges and swells at base in fruiting phase, lobes hardening into spines. Stamens 5, united with calyx-tube. Gynoecium composed of 2 fused carpels. Inflorescence a dense cyme.
- Leaves: First year a basal rosette, second year usually only alternate. Rosette leaves stalked, stem leaves amplexicaul. Leaf blade elliptic–ovate, large-toothed–pinnatifid.
- Fruit: 1.5 cm (0.6 in.) long circumscissile capsule protected by an urceolate (pitcher-shaped) calyx.
- Habitat: Waste ground, roadsides, yards, gardens, soil heaps, fields, church lands, ruins, mills, harbours.
- Flowering time: June–September.
Henbane often grows around long-inhabited areas and old fortifications. Its seeds can remain viable for a very long time, and have been proved to be viable for at least 118 years, and probably a lot longer. The seeds require a high temperature to germinate, and even a little shade will stop them sprouting. When the land is dug, the seeds awaken from their big sleep. In the first year the plant develops a large leaf rosette, which can at first glance look like cabbage – but its sticky glandular hairs, eye-catching straight hairs and strange smell soon clear up any misunderstanding. It blooms in its second – and final – year, by which time the leaf rosette has withered. Yellowish brown-and-black-flecked flowers probably attract mainly blowflies to pollinate the plant. Up to tens of thousands of seeds can ripen inside the capsule, which fall once more to the earth.
Henbane is highly poisonous. The whole plant contains e.g. tropane alkaloids such as hyoscyamine, atropine and scopolamine, and the seeds contain a group of less poisonous alkaloids. Henbane was second only to monkshood as a favourite of poison-makers in the Middle Ages. Mild poisoning causes symptomatic madness. Many witches who were burned at the stake had perhaps used henbane and thought that they could fly or that they had met the devil. Although henbane is poisonous, its medicinal qualities have been known for centuries. It was especially valued in surgery for its undeniable narcotic effect. It was believed to effectively treat many kinds of ailments, from sea-sickness to earache, and from arthritis to toothache. Its active ingredients are important medicinal compounds: scopolamine is an ingredient in travel sickness patches and atropine is routinely used by opticians.
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