Hypericum perforatum subsp. perforatum
Klamathweed, Klamathweed
(c) Douglas Goldman, some rights reserved (CC BY-SA), uploaded by Douglas Goldman · licence
Family: Hypericaceae · Type: Perennial · Not Native
Conservation status: Cal-IPC Yes
Hypericum perforatum subsp. perforatum (Klamathweed) is a non-native California perennial in the Hypericaceae family, recognized by numerous black-dotted flowers and rolled leaf margins.
Klamathweed is a naturalized perennial herb found in northwestern California, the Cascade Range, northern and central Sierra Nevada, and Sacramento Valley in open, disturbed areas at elevations of 6 to 1,980 meters. Flowering from May to August, this plant produces bright yellow flowers with dense black gland dots that twist and fade with age, arranged in clusters of 25 to 100 per stem. Growing with erect stems 30 to 120 centimeters tall, emerging in many clusters from the base with sterile axillary branches. Its narrow oblong leaves have distinctive rolled margins and are marked with black and clear dots, particularly noticeable on the lower surface. The fruit is unlobed and approximately 7 to 8 millimeters long.
Identification and appearance
Key characters: 6 sympatric species; diagnostic numerous black-dotted flowers and rolled leaf margins
Habitat and range
Habitat: Open, disturbed areas in many plant communities
Elevation: 6-1980 m
Outside California: to eastern North America, native to Europe
Bloom period
Hypericum perforatum subsp. perforatum blooms May-Aug.
Conservation status
Cal-IPC Yes
How to tell it apart
vs Euphorbia: Euphorbia has milky sap and tiny flowers in cups; Hypericum has clear sap and showy yellow flowers.; vs Lysimachia: Lysimachia has stamens separate, not bundled; Hypericum's stamens cluster into 3-5 distinct bunches.; vs Lonicera: Lonicera is a woody vine or shrub; Hypericum is herbaceous with opposite leaves.; vs Dendromecon: Dendromecon is a woody shrub with 4 petals; Hypericum is herbaceous with 5 petals.; vs Mentzelia: Mentzelia has rough, sandpapery leaves; Hypericum has smooth leaves with translucent dots.
Frequently asked questions
Is Hypericum perforatum subsp. perforatum native to California?
No. Hypericum perforatum subsp. perforatum is not native to California (recorded as not native).
When does Hypericum perforatum subsp. perforatum bloom?
Hypericum perforatum subsp. perforatum blooms May-Aug.
What plant family does Hypericum perforatum subsp. perforatum belong to?
Hypericum perforatum subsp. perforatum is in the Hypericaceae family, genus Hypericum.
Is Hypericum perforatum subsp. perforatum invasive in California?
Hypericum perforatum subsp. perforatum is listed by Cal-IPC with an invasiveness rating of Yes.
What habitat does Hypericum perforatum subsp. perforatum grow in?
Hypericum perforatum subsp. perforatum grows in Open, disturbed areas in many plant communities.
Related species
Other California species in the same genus, family, or bioregion.
Sources: Jepson eFlora · CalPhotos
Last updated 2026-09-30
Data from The California Species Project — 14,000+ California species with verified data from CNPS, CDFW, USFWS, Cal-IPC, and more.