Black horehound (Ballota nigra) is an early sprouting plant and its leaves appear at the beginning of March.
The young leaves are roundish to heart-shaped, while the older leaves at the top of the shoots are ovate-lanceolate. They can grow up to 10 cm long with the stem.

Habitus & biology
Ballota nigra is a perennial plant that can grow up to one meter in height. It blooms from June to October and the flowers can be dark pink to almost white in color.
Origin & habitats
Black horehound is native to Europe, North Africa, West Asia and the Caucasus (source). It grows in sunny to semi-shady locations on embankments, in front of bushes or hedges, along roadsides and on or near walls.

Botany
Botanically, Ballota nigra belongs to the Lamiaceae family. It is therefore not related to stinging nettles.