Ballota, commonly known as black horehound or hoarhound, is an herbaceous perennial of the laminaceae, or mint, family. Some people call it stinking or fetid horehound because the plant may have a strong odor and the leaves turn black as the plant dies, which is possibly why people call it black horehound. The name ballota might be from the Greek ballo, meaning reject, and may refer to the fact that cattle usually do not eat it. The leaves, buds, and flowers have small white hairs on them, giving the plant a hoary appearance. Although gardeners generally do not raise it ornamentally, some people use it for medicinal purposes.
Sometimes growers use the name Marrubium nigrum, which might stem from the Maltese name Marrubja sweda. It is a native of the Mediterranean area, parts of Europe, and some parts of western Asia. In its natural area, it usually grows in nearly barren, rocky terrain. From a distance, a person may detect an aromatic scent from the flowers, but closer to the plant a person generally notices a strong offensive odor that the rest of the plant emits.
Depending on some factors, such as growing conditions, cultivar, and other aspects, the plant may grow from 16 to 51 inches (40 to 130 cm) tall. The square mint-like stem is basal branching, sporting leaves that grow in opposite pairs that alternate at right angles to the pairs above and below. The leaves are obovate, meaning they are egg-shaped and taper toward the stem. The leaf surface is rugose, or wrinkled, and green to dark green.
The ballota's small flowers are labiates, meaning that they have lips like snapdragon flowers do. The lips rise from fused sepals that create a funnel generally between one-third and one-fourth of an inch (eight to 12 mm) long. The hairy, slightly concave upper lip has two lobes, and the glabrous, or hairless, lower lip has three to four lobes, giving the flower an exotic appearance. The white to lilac-colored flower has four long stamens with yellow anthers rising up the funnel to just under the upper lip.
When fertilized, the flower develops into a fruit that consists of four nutlets containing black seeds, and growers propagate ballota plants by sowing these seeds. In past centuries, herbalists used tonics from the ballota for respiratory ailments, convulsions, and as a mood stabilizer. In modern times, some people still use it for bronchial problems and nervous dyspepsia. People often use extracts of the plant for travel sickness, arthritis, and gout. Ginger root is replacing most applications for the plant's herbal use.