Flaxleaf Plainsmustard, Flaxleaved Plainsmustard, Lava Cress, Plains Mustard, Rush Mustard, Salmon River Plainsmustard

Plains mustard is a rhizomatous perennial with erect or lax, broomlike stems from 20-70 cm tall. The stems are usually unbranched, though loose branching may occur.

The leaves are simple and linear, from 2-9 cm long and 1-4 mm wide with entire margins the norm, although some serration or pinnatifid lobes may occur.

The racemes are long with yellow flowers. The 4 sepals are 4-5 mm long and the 4 petals are slightly longer at 6-10 mm. The seed capsules are thin siliques, which are held nearly erect. They range from 2.5-5 cm long and about 1 mm wide.

Plains mustard is a plant of sagebrush plains, grasslands, and the lower mountains.

Plains mustard is found from British Columbia south through Washington and Oregon to Nevada, and hence east to Montana and New Mexico.

In the Columbia River Gorge, it may be found Hood River, OR and The Dalles, OR between the elevations of 100'-400'.