There are three species of Cornus (dogwood) native to Washington State; Cornus nuttalii is a tree; Cornus unalaschkensis is a 4” ground cover; and Cornus sericea is a shrub.
Redtwig (or red osier) dogwood ranges over most of Canada and the U.S., being absent from only the SE corner of the United States. There are two recognized sub-species, ssp. occidentalis, found along the West Coast, and ssp. sericea, found throughout the species range. Ssp. occidentalis has ridged stones, generally hairier leaf undersides, and slightly larger flowers; ssp. sericea has smooth stones, glabrous to strigose leaves, and slightly smaller flowers (Jepson). Hitchcock posits that these traits form a continuum rather than two distinct forms.
Cornus sericea is a stoloniferous wetland shrub, tolerant of saturated soils, and even of some standing water. It has excellent soil binding capabilities. Horticulturally, it is popular for its bright red twigs in winter (It is often coppiced to enhance their effect). There are many cultivars available, most chosen for the color of their twigs.
Redtwig dogwood has clumps of small, white flowers in late spring that are an important nectar source for butterflies, and it is a larval host for the Spring Azure (Celastrina echo), which lays its eggs on the flower buds. Many bird and mammal species eat the berries, and help in seed dispersal. (Bears are purported to love them). The stems are an important browse for ungulates, and stands can be heavily affected by cattle grazing.
While the berries are bitter to humans, some native peoples did use them as food. Cornus sericea is also used in traditional medicine, and the twigs are used in basketry.