Distribution: Chiefly along the Columbia River in Washington, south to the Willamette Valley.
Habitat: Low ground, especially in places submerged in spring and drier in summer.
Conservation Status: Threatened in Washington (WANHP)
Herbaceous perennial from fibrous roots and a short, simple crown, the stems 1.5-5 dm. tall, divaricately branched, often from near the base.
Basal leaves without blades, the petioles elongate, hollow; cauline leaves with progressively shorter petioles, the blades narrowly elliptic, up to 1 cm. wide, sub-entire or with spiny teeth.
Flowers sessile in heads up to 1 cm. wide; involucral bracts narrow, spine-toothed, much surpassing the flowers; bracteoles subtending the flowers narrowly linear, also exceeding the flowers; calyx lobes 5, 3 mm. long, acuminate; corolla 5-lobed, white.
Fruit ovoid, 2 mm. long, covered with tapering scales 1-1.5 mm. long.