The photo above shows a close-up of the flowers and spreading, linear fruit capsules of Jim Hill mustard as seen about one mile east of Celilo, OR............mid March, 2005. Note how the narrow sepals are arched slightly and how they have hooded tips. Note also the stout pedicels below each flower or fruit in both the photo above and below, another characteristic of this species.
Jim Hill mustard is an annual or winter annual, which is found as a weedy species over much of the United States. It is an erect, freely branched plant with stiff hairiness near the base and smooth herbage above. Viewed from a distance, it has a bushy appearance. The stems range from 30-150 cm tall. The leaves are alternate, with the lower leaves coarsely divided into broad lobes or leaflets. The upper leaves are reduced in size with finer or narrower lobes or segments. The leaf blades are lanceolate, oblong or oblanceolate and measure up to 15 cm long. The lower blades are pinnatifid roughly equal-sized segments, or pinnatifid with the terminal segment the larges. The upper blades are pinnatifid into long thin segments.
The inflorescence consists of numerous racemes at the ends of branches, with each flower having 4 sepals (about 4 mm long) and 4 pale yellow petals from 6-8 mm long. The seed capsules are long, linear siliques from 5-10 cm long.Plants often break off at soil level when mature, tumbling across the landscape, scattering seeds with the wind.
Tumble mustard is common in small grain fields, rangeland, along roadsides, and in open disturbed areas.
Although it is a native of Europe, Jim Hill mustard is found over much of the United States.