Trifolium incarnatum
Crimson clover
no rights reserved · CC0
Family: Fabaceae · Type: Herb · Not Native
Trifolium incarnatum (Crimson clover) is a non-native California herb in the Fabaceae family, recognized by unique cylindrical spike inflorescence distinguishes from all others.
Crimson clover is a naturalized annual found in the California Floristic Province, especially in disturbed areas at elevations below 300 meters. Flowering from May to August, this plant produces crimson or white flowers in dense spike-like inflorescences 2 to 6 centimeters long. Growing with erect, generally unbranched hairy stems, it forms an upright annual habit. Its leaves have three leaflets 1 to 2.5 centimeters long, which are obovate to heart-shaped, with prominent veined stipules. The distinctive flower has a calyx 7 to 10 millimeters long with bristle-like lobes and crimson petals reaching 10 to 14 millimeters in length.
Identification and appearance
Key characters: 68 sympatric species; unique cylindrical spike inflorescence distinguishes from all others
Habitat and range
Habitat: Uncommon. Disturbed areas
Elevation: especially < 300 m
California counties: Monterey, Butte, Madera, Humboldt, Sonoma, San Bernardino, Orange, San Luis Obispo, Contra Costa, San Francisco, Fresno, Napa, Placer, Santa Clara, Riverside, Glenn, Santa Barbara, Solano, Nevada, Santa Cruz, Amador, Mendocino, Siskiyou, Lake, Sutter, Tehama, Marin, San Diego, Alameda, Sacramento, Ventura, Tuolumne, El Dorado, Stanislaus, Yolo, Imperial
Outside California: naturalized in southeastern United States, native to southern Europe
Bloom period
Trifolium incarnatum blooms May-Aug.
How to tell it apart
vs Medicago: Trifolium flowers persist around fruits; Medicago flowers fall off leaving exposed coiled fruits.; vs Oxalis: Trifolium has pea-shaped flowers; wood-sorrels (Oxalis) have 5-petaled star-shaped flowers and heart-notched leaflets.; vs Melilotus: Trifolium flowers persist enclosing fruits; Melilotus flowers fall off leaving exposed ridged pods.; vs Castilleja: Trifolium has pea flowers and 3 toothed leaflets; paintbrush (Castilleja) has tubular flowers in colorful bracts.; vs Acmispon: Trifolium leaflets have toothed edges; Acmispon leaflets have smooth untoothed margins.
Frequently asked questions
Is Trifolium incarnatum native to California?
No. Trifolium incarnatum is not native to California (recorded as not native).
When does Trifolium incarnatum bloom?
Trifolium incarnatum blooms May-Aug.
Where in California does Trifolium incarnatum grow?
Trifolium incarnatum occurs in Monterey, Butte, Madera, Humboldt, Sonoma, San Bernardino, Orange, San Luis Obispo and other counties, at elevations of especially < 300 m.
What plant family does Trifolium incarnatum belong to?
Trifolium incarnatum is in the Fabaceae family, genus Trifolium.
What habitat does Trifolium incarnatum grow in?
Trifolium incarnatum grows in Uncommon. Disturbed areas.
Related species
Other California species in the same genus, family, or bioregion.
Sources: Jepson eFlora · Index of California Plant Names · CalPhotos
Last updated 2026-10-07
Data from The California Species Project — 14,000+ California species with verified data from CNPS, CDFW, USFWS, Cal-IPC, and more.