Mustards have been cultivated for their seeds for over 5 000 years.
White/yellow mustard is a native of the Mediterranean, central Asia, and North Africa.
Brown mustard originated in Asia and should not be confused with black mustard which despite popular opinion is a different species of brassica, being Brassica Nigra.
Mustards, which are annuals, generally grow from 60 to 120 cm (2 to 4 feet) tall. Both mustards also grow in the wild as weeds. White and brown mustard are seed mustards, and should not be confused with vegetable mustards, such as mustard greens. Although seed mustard leaves are edible, vegetable mustards have a superior taste. Both mustards have pungent-flavoured, broad, dark green, deeply cut lower leaves. Upper leaves are much less dissected, especially in brown mustard.
Stem and branches are usually hairy in white/yellow mustard, slightly hairy in brown mustard. Both mustards produce loose clusters of yellow flowers, beginning about 5 to 6 weeks after the seedlings emerge. White mustard flowers are somewhat larger than those of brown mustard. White mustard seed pods stand out from the stem and have a long, beak-like tip. Brown mustard seed pods, which form closely to the plant’s stem, have a plump, cylinder-like shape when ripe.
White/yellow mustard seeds are white or yellow, odourless, and have a milder flavor than brown mustard seeds. Brown mustard seeds are brown or dark yellow, and give off a distinctly irritating odour when crushed. Leaves, flowers, and seeds of both mustards may be eaten.
Mustards have been used in traditional folk medicine as a stimulant, diuretic, and purgative, and to treat a variety of ailments including peritonitis and neuralgia.
In culinary terms, ground down, the seeds are made into a condiment paste in the west but in the east, the seeds are often popped when lightly heated either by dry roasting or shallow frying to impart their heat and flavour in spicy paste mixes that form the basis of many a curry.