Brassica Nigra
Brassica nigra, or black mustard, is an annual plant cultivated for its black or dark brown seeds, which are commonly used as a spice. It is native to tropical regions of North Africa, temperate regions of Europe, and parts of Asia.
It is an upright plant, with large stalked leaves. They are covered with hairs or bristles at the base, but on the stem smoother. It can reach up to 80–90 cm (31–35 in) tall or even up to 2.4 m in moist fertile soil. It blooms in summer, from May (in the UK) onwards. The flowers have four yellow petals, which are twice as long as the sepals. Each stem has around four flowers at the top, forming a ring around the stem. Later, the plant forms long seed pods, that contain four rounded seeds.