Ballota nigra aka Black Horehound

Ballota nigra, or black horehound, is in the mint family. This family bears the name Lamiaceae. Its native range spans Macaronesia, Europe, the Mediterranean region and Iran. Britain and Ireland also form part of its native range. It lives for more than one year in temperate regions. Wild plants grow on waste ground, by hedges and in woods. They grow in shade too. They favour loose, moist soil rich in nitrogen.

Garden plants reach about 1.6–3.3 feet [0.5–1 metre] tall and wide. They form bushy clumps that stand upright or sprawl. Plants take about two to five years to reach full size. They are semi-evergreen, keeping some leaves through winter. The simple leaves have an egg shape and coarse teeth. Their surface feels rough. Their colour ranges from mid-green to pale green. The leaves give off a foul smell when bruised. This scent helps explain two of the plant's other names. These are stinking horehound and fetid horehound.

The small, dull purple flowers grow in whorls, or rings. Their soft colour suits loose garden schemes without a formal layout. The RHS suggests this species for cottage gardens and wildflower meadows. It also suggests it for wildlife gardens. PFAF lists it for gardens in woods. These include spots with patchy shade and shaded edges. These uses reflect where the plant can grow. It suits both open sites and those with some shade.

For garden use, the RHS advises full sun and well-drained soil. It also lists part shade as suitable. Choose a site with shelter. Listed options include sites that face south or west. The plant can grow in chalk, loam and sand. It accepts acid, neutral and alkaline soil. The stated soil moisture range runs from dry to moist. The RHS gives it a hardiness rating of H4. PFAF lists USDA zones 7–10. Divide plants in spring to make new ones. It needs no routine pruning. Disease is rare, but leafhoppers may attack it.

PFAF lists no known food uses. It gives edibility a score of zero out of five. It also lists no known hazards. This does not mean it guarantees the plant is safe. Black horehound has a long history of use as a herb. Past uses include treating nausea and muscle spasms. Its bad taste has limited its use in modern herbal care. Experts differ on the worth of some older treatments. These records describe past uses, not proven benefits. They do not give guidance for treatment at home.