Hypericum scouleri, known by the common name Scouler's St. John's wort in English, is a flowering species of plant from western North America.

[3] The leaves are attached on opposite sides of the stems at the nodes and usually spread outwards, but occasionally they may point upwards instead.

In addition Common St John's wort has more branched stems and its flowers are in a cluster with a flat top.

[9] Other sources, such as the USDA Natural Resources Conservation Service PLANTS database, continue to list two subspecies, Hypericum scouleri ssp.

[11] Hooker named the species scouleri to honor the naturalist John Scouler who accompanied David Douglas on his expedition to the Columbia river in the 1820s.

[12] It is also called Western St. John's wort on occasion,[13] however this name is more commonly applied to Hypericum formosum.

[9] Hypericum scouleri perfers moist locations such as streambanks and openings in well watered quaking aspen groves.

[16] The klamathweed beetle (Chrysolina quadrigemina) was introduced to North America as a biological pest control agent for Common St. John's wort.

Though in laboratory tests the beetles do successfully complete their lifecycle on Hypericum scouleri and related native species, it has not been reported to feed on it in natural conditions.

[17] In 2019 NatureServe evaluated Hypericum scouleri as globally secure (G5), meaning it has no significant threats or known declines in population.