Purple mustard, musk mustard, blue mustard
All the western states (non native)
Between 4 and 15 inches
Disturbed ground, roadsides, wasteland, washes, fields
Lanceolate to oblong to oblanceolate, up to 3 inches long, with wavy, shallowly lobed or toothed edges
Chorispora tenella originates in Europe and Asia but has long been introduced in the US, where it can be very abundant, carpeting whole fields; the species is classed as a noxious weed in many areas. Leaves and stems have a sparse covering of sticky, glandular hairs; white stalks, often topped by a light brown gland. Plants produce small numbers of flowers towards the stop of the stem, blooming over a period of several months.
Flowers are formed of four greenish-purple sepals, partly fused into a tube a quarter of an inch long, and four spreading magenta-pink petals, narrow (clawed) at the base and similar in length to the sepals. The fruit is a gently upwards-curved green pod, up to 2 inches long. The plant exudes a strong, musky aroma.