Leaves

Leaves are opposite and decussate (alternating opposite pairs, each pair at right angles to the next), and range from oval-lanceolate to heart-shaped, with crenate or dentate border. Dark green and usually hairy, upper face is wrinkled, with a net-like vein pattern.

Flowers

Organized in clusters around the stem, with 15 to 30 flowers. It has an actinomorphic calyx (length 9–10 mm, width 7 mm), made up by five sepals fused together in a tube with five teeth; and a labiate corolla of 12–13 mm, ranging from pink to pale purple to withish. The classic mint-shaped flower.

Seeds

Stem

It has herbaceous ascending stems, wooden and branched at bottom. Like other mint family members, it has a square cross-section and is covered in down-folded hairs.

Fruit

Each fertilized flower produces a group of 5 black nutlets, cylindrical to ovoid, 2 mm long, partially or fully covered by the calyx. The basal end is flat and attached to the receptacle, while the top end is rounded or pointed.

Taste

Whilst it is not toxic and will do you no harm, it has a pungent musty, rotten smell and the taste is not much better; Although I have seen people try it and say that they like it!

Frequency & law

Very common and not restricted.

Possible confusion

Other members of the mint family, especially dead-nettles, woundworts, etc. Superficially stinging nettles too, but only at a glance.

Habitat

Black horehound prefers nitrogen rich soil, and so is often found with stinging nettles and dead nettles; Frequently found on wasteland, near water and usually where people have occupied at some point in the past. It likes loose, alkaline soils and survives frosts down to -10C.

How to harvest

Flowers between June and September and is usually gathered when flowering.

Cooking tips

Whilst it is not toxic and will do you no harm, it has a pungent musty, rotten smell and the taste is not much better; Although I have seen people try it and say that they like it!

Other uses

Black horehound has a long history of herbal use, though is not widely employed in modern herbalism because of its unpleasant flavour.

Folklore

The name Ballota comes from the Greek ballo (to reject), because of the strong offensive odour of the plant; cattle will not eat it. The specific name nigra refers to the black colour of dried leaves.