Hyoscyamus niger aka Common Henbane

Hyoscyamus niger, or black henbane, belongs to the nightshade family. Kew places its native range from the Mediterranean to Iran. It now grows in parts of the United States. People brought it there for use as a medicinal herb. It grows on roadsides, waste ground, and rocky sites. It also occurs near buildings, on coasts, and on lower mountain slopes.

This upright herb lives for one or two years. Young plants form a rosette before their stems rise. Two-year plants branch more than those that flower in one year. The green stems have coarse hairs. The green leaves grow in an alternate pattern along them. Each leaf is simple, with lobed or toothed edges. Fine hairs give the leaves a soft but sticky feel. Lower leaves have short stalks; upper leaves lack them. The plant has an unpleasant smell and taste that deter animals.

Flowers open in summer and autumn. One-year plants bloom later than two-year plants. The flowers grow where leaves meet the stems. Their five joined petals form a tube or cup. Purple veins mark the pale yellow to greenish-yellow surface. Long hairs cover the base of each flower. The flowers have a stale, fish-like scent. Egg-shaped seed capsules follow the blooms and split when ripe. Each capsule can hold as many as 200 seeds.

Plants For A Future recommends sun and dry soil. NC State also lists shade as suitable. Good drainage matters, since the plant does not tolerate wet soil. It grows in loam, sand, and shallow rocky ground. Sources list a broad soil pH range, though alkaline soil is preferred. NC State lists USDA zones 4–8 and a moderate growth rate. Older plants transplant poorly because their taproots break with ease. Showy flowers offer some garden interest, but self-seeding makes it invasive. Seeds can stay viable for many years. NC State reports no major pest or disease problems.

Henbane has a long history of medicinal use for pain and sedation. That history does not make it safe for home treatment. All parts contain highly toxic compounds called tropane alkaloids. The plant poisons people, pets, horses, and wildlife. Swallowing it can cause vomiting, seizures, coma, and death. It has no known food use. NC State advises gloves when handling it because skin exposure may cause a rash.