Pseudotrillium is a proposed monotypic genus of flowering plants containing the single species Pseudotrillium rivale, which is known by the common name brook wakerobin. The genus was proposed in 2002 on the basis of morphology and molecular evidence that suggest the plant should no longer be included in genus Trillium. This species is endemic to the Siskiyou Mountains of southern Oregon (Josephine, Coos, Douglas, + Curry counties) and northern California (Siskiyou + Del Norte counties), usually on soils of ultramafic origin, such as serpentine. Pseudotrillium rivale is a rhizomatous perennial growing up to 20 centimetres (8 in) in height. The three bracts have generally lance-shaped blades up to 11 centimetres (4 1⁄3 in) long borne on petioles. The blades are glossy blue-green with silvery venations. Atop the whorl of bracts is a single nodding non-fragrant flower with green sepals and pink-blushed white petals up to 3 centimetres (1 1⁄4 in) long by 2 centimetres (4⁄5 in) wide. This plant has gained the Royal Horticultural Society's Award of Garden Merit.
Riparian woodlands by a brook leading into the Smith River in Hiouchi, California