Black mustard is often cultivated for its edible seed, though it is going out of favour because it rapidly sheds its seeds once they are ripe and this makes it harder to harvest mechanically than the less pungent brown mustard (Brassica juncea).. This is used especially as a food flavouring, though it is also sown with the seeds of garden cress (Lepidium sativum) to provide mustard and cress, eaten when the seedlings are about one week old.
Black mustard is also grown as a medicinal plant.
It germinates freely and quickly grows rapidly and makes a very useful green manure. The plants are not very winter hardy so the seed is best sown in the spring when grown for its seed whilst it can be sown as late as late summer as a green manure crop.
The flowers have a pleasing perfume, though this is only noticed if several flowers are inhaled at the same time
A semi-drying oil is obtained from the seed, as well as being edible it is also used as a lubricant, illuminant and in making soap.
The plant is often grown as a green manure, it is very fast, producing a bulk suitable for digging into the soil in about 8 weeks. Not very winter hardy, it is generally used in spring and summer. It does harbour the pests and diseases of the cabbage family so is probably best avoided where these plants are grown in a short rotation and especially if club root is a problem.
The flowers have a pleasing perfume, though this is only noticed if several flowers are inhaled at the same time.
Note: When eaten in large quantities, the seed and pods have sometimes proved toxic to grazing animals.
An easily grown plant, black mustard is suited to many types of soils except very heavy clays, it grows best on light sandy loams, or deep rich fertile soils. Succeeds in full sun in a well-drained fertile preferably alkaline soil.
Sow in situ from early spring until late summer in order to obtain a succession of crops. The main crop for seed is sown in April.
Leaves - raw or cooked. A hot flavour, they can be finely chopped and added to salads or cooked as a potherb. The seedlings can also be used when about one week old, adding a hot pungency to a salad.
Immature flowering stems - cooked and eaten like broccoli. Mustard seed is commonly ground into a powder and used as a food flavouring and relish. This is the black mustard of commerce, it is widely used as a food relish and as an ingredient of curry. Pungency of mustard develops when cold water is added to the ground-up seed - an enzyme (myrosin) acts on a glycoside (sinigrin) to produce a sulphur compound. The reaction takes 10 - 15 minutes. Mixing with hot water or vinegar, or adding salt, inhibits the enzyme and produces a mild bitter mustard. The seed can also be used whole to season pickles, curries, sauerkraut etc. Black mustard has a stronger more pungent flavour than white mustard (Sinapis alba) and brown mustard (B. juncea).
An edible oil is obtained from the seed.