Tansy mustard

Descurainia pinnata, commonly known as tansy mustard or western tansy mustard, is an annual herb in the family Brassicaceae widespread across western and southern North America from southern Canada to northern Mexico, where it inhabits desert grasslands, sandy washes, roadsides, and disturbed ground. Germinating with autumn or winter rains, it forms a basal rosette of finely twice- to thrice-pinnately divided, fern-like leaves with short, soft, often glandular hairs. In spring the plant produces erect, branched flowering stems 15-80 cm tall bearing elongated racemes of numerous tiny four-petalled flowers, pale yellow to dull cream-yellow and only 1-2 mm wide. The fruits are slender, club-shaped to oblong-cylindric siliques 5-15 mm long, held on slender, ascending pedicels and containing two rows of minute reddish-brown seeds per locule that become mucilaginous when wetted.