Ballota nigra has a very strong characteristic smell reminiscent of mold or humidity, and can be recognized by its clusters of hairy, reddish-purple flowers.

Leaves are opposite and decussate, and range from oval-lanceolate to heart-shaped, with crenate or dentate border.

There are four didynamous stamens, running parallel under the upper lip, with glabrous filaments and yellow anthers.

Each fertilized flower produces a tetrad of black nutlets, cylindrical to ovoid, 2 mm long, partially or fully covered by the calyx.

The name Ballota comes from the Greek ballo (to reject), because of the strong offensive odor of the plant; cattle will not eat it.

Ballota nigra is a nitrophilous plant; it grows in ruins, fallows, and hedges at elevations up to 1300 m. It prefers loose, calcareous (alkaline) soils.