Black mustard leaves and sprouts can be eaten raw or cooked. The seeds are used as a spice. They can also be further processed into mustard powder and used for mustard mixes. Mustard poultices help against bronchitis and relieve rheumatic discomfort. Black mustard grows wild in Central Europe.
From Wikipedia: “Brassica nigra (black mustard) (Sanskrit: राजक्षवक, rajakshavak; Marathi: काळी मोहरी, Kali Mohari) is an annual plant cultivated for its seeds, which are commonly used as a spice.”
Origin and distribution:
“Black mustard is found in large areas of Africa, Europe, and Asia and is native to the eastern Mediterranean region. It has been grown in Central Europe since Roman times and since the sixteenth century has been known as a neophyte here, where it thrives in river valleys. In Central Europe, this domesticated plant that has become wild is seen as an invasive plant or agriophyte.”
“When the fields bloom yellow a second time in the late summer or fall, this is often black or white mustard that is covering the soil as a catch crop in order to prevent or reduce the loss of nutrients — especially nitrate — it is then later plowed under to enrich the humus (green manure).*”
“The spice is generally made from ground seeds of the plant, with the seed coats removed. The small (1 mm) seeds are hard and vary in color from dark brown to black. They are flavorful, although they have almost no aroma. ...
The plant itself can grow from two to eight feet tall, with racemes of small yellow flowers. These flowers are usually up to 1/3" across, with four petals each. The leaves are covered in small hairs; they can wilt on hot days, but recover at night.
Since the 1950s, black mustard has become less popular as compared to India mustard because some cultivars of India mustard have seeds that can be mechanically harvested in a more efficient manner.”
Culinary and medicinal uses:
“The seeds are commonly used in Indian cuisine, for example in curry, where it is known as rai. The seeds are usually thrown into hot oil or ghee, after which they pop, releasing a characteristic nutty flavor. The seeds have a significant amount of fatty oil. This oil is used often as cooking oil in India.
In Ethiopia, where it is cultivated as a vegetable in Gondar, Harar and Shewa, the shoots and leaves are consumed cooked and the seeds used as a spice. Its Amharic name is senafitch.
Ground seeds of the plant mixed with honey are widely used in eastern Europe as cough suppressant. In Eastern Canada, the use of mouche de moutarde to treat respiratory infections was popular before the advent of modern medicine. It consisted in mixing ground mustard seeds with flour and water, and creating a cataplasm with the paste. This cataplasm was put on the chest or the back and left until the person felt a stinging sensation.”
Note (italics): * = Translation from a German Wikipedia entry