Formerly known as the Cruciferae, because it has four petals held open in the shape of a cross, this family includes many important vegetables and agricultural crops. There are over 3000 species throughout the world, but the largest number are from temperate regions of the Northern Hemisphere. Several have bright yellow flowers and can be difficult to distinguish from each other before fruits have formed. Identification therefore often relies on the presence of mature fruits. The fruits may have a 'beak' at the end and are often divided internally by a longitudinal partition. For identification purposes, the family is usually divided into those species with fruits more than three times as long as broad (excluding the 'beak'), in which case the fruit is termed a siliqua, and those in which they are less than three times as long as broad, in which case the fruit is referred to as a silicula.
Guide to Identify Presented Species of the Mustard Family
FLOWERS PURPLE (WHITE), FRUITS LONG AND LINEAR
Chorispora tenella Musk Mustard Branched annual, flowers about 1 cm wide. Leaves basal and alternate, shallowly toothed. Fruit pods curved upward, with long, pointed beak.
SLENDER PLANTS, FLOWERS WHITE OR PINK, FRUITS LONG AND LINEAR
Arabis Rock Cress Slender plants, often hairy, mostly perennials. Leaves basal and alternate, entire, narrow. Fruit pods linear, thin, flattened, 2-7 cm long.
Cardamine Bittercress Flowers white, about 1 cm wide. Leaves mostly pinnately or palmately divided. Fruit pods linear, cylindrical, 20-35 mm long. Wet locations.
Cardaria Whitetop Perennials, flowers in wide, dense clusters. Leaves alternate, oblanceolate, sharp-toothed. Fruit pods rounded, inflated, about 5 mm long.
Thlaspi Pennycress Hairless plants with white flowers ca 5-10 mm wide. Leaves alternate, hairless, broadly lance-shaped. Fruit pods rounded or wedge-shaped, flattened.
FLOWERS WHITE OR YELLOW, FRUITS SHORT AND ELLIPTICAL
Draba Draba Mostly small, slender mountain plants. Leaves alternate, often small and narrow, mostly entire. Fruit pods mostly lance- or egg-shaped, ca 3-20 mm long.
FLOWERS WHITE OR YELLOW, FRUITS SHORT AND FLATTENED
Alyssum Madwort Small biennials, flowers yellow, 3-4 mm wide. Leaves alternate, small, narrow, entire. Fruit pods rounded, 3-4 mm long, flattened.
Lepidium Peppergrass Flowers very small, numerous, in dense, tall clusters. Leaves mostly pinnately cut into narrow lobes. Fruit pods obovate, short, about 2-3.5 mm long.
FLOWERS YELLOW, FRUITS LONG AND LINEAR
Descurainia Tansy-mustard Slender plants, flowers small, petals narrow. Leaves deeply cut 2-3 times into narrow lobes. Fruit pods linear or club-shaped, 10-30 mm long.
Erysimum Wallflower Mostly flat-hairy plants with showy flowers. Leaves many, alternate, narrowly lance-shaped. Fruit pods linear, thin, cylindrical, 1-10 cm long.
Sinapis arvensis Charlock Mustard Annual, branching and leafy, flowers yellow, 15-20 mm wide. Leaves basal and alternate, with large ending leaflet. Fruit pods linear, 4-5 cm long, quite thick, lined, with long beak.
Sisymbrium Tumble-mustard Plants tall, leafy, branched, flowers often showy. Leaves alternate and basal, often pinnate. Fruit pods linear, very thin, 10-30 mm long.
Alphabetical listing with links to presented species of the Mustard family: