Sinapis alba seeds can be ground into a powder and used as a food flavouring, it is the 'white mustard' of commerce. This is milder than the black mustard obtained from Brassica nigra.

The plant can be grown as a green manure crop. It is very fast growing, producing a good bulk in just a few weeks from seed, but it is shallow rooted so does not do so well in dry periods.

White mustard is a quick-growing long-day annual which prefers temperate climates with some humidity. It is sometimes cultivated, both in the garden and commercially, for its edible seed. The plant can withstand high temperatures, but very hot days during flowering and ripening may reduce seed setting and lower quality of seed.

It is a very fast growing plant, but requires plenty of moisture for optimum growth.

Prefers a light well-drained soil. Succeeds on most soils when growing in a sunny position. For best production, it requires high nutrient soils with a high level of nitrogen, but it may be grown on a wide range of soils from light to heavy, growing best on relatively heavy sandy loamy soils. It is not suited to very wet soils.

Sow in situ from early spring to late summer. Germination takes place in less than a week. The earlier sowings are for a seed crop, the later sowings are for edible leaves and green manure.

When sowing seed for use in mustard and cress, the seed is soaked for about 12 hours in warm water and then placed in a humid position. Traditionally, it is sown in a tray on a thin layer of soil, or on some moist blotting paper, and the tray is placed in a warm dark place for a few days to encourage rapid and rather etiolated growth. The seedlings can then be placed in a lighter position for a couple more days to turn green before being eaten. The mustard seed should be sown about 3 - 4 days later than the cress for them both to be ready at the same time.

Edible uses

Leaves - raw or cooked. A hot pungent flavour, especially if eaten raw. Young leaves are used as a flavouring in mixed salads, whilst older leaves are used as a potherb.

Seed - sprouted and eaten raw. The seed takes about 4 days to be ready. A hot flavour, it is often used in salads.

Note: The seed contains substances that irritate the skin and mucous membranes. The plant is possibly poisonous once the seedpods have formed.

http://practicalplants.org/wiki/Sinapis_alba