Phacelia thermalis
Heat phacelia
(c) Matt Berger, some rights reserved (CC BY), uploaded by Matt Berger · licence
Family: Hydrophyllaceae · Type: Herb · Native
Phacelia thermalis (Heat phacelia) is a native California herb in the Hydrophyllaceae family, recognized by stiff glandular hairs and sepals with raised veins.
Heat phacelia is a California native annual found in the eastern Cascade Range and Modoc Plateau in open clay flats at elevations of 1,000 to 1,700 meters. Flowering from May to August, this plant produces white to pale blue flowers 3 to 4 millimeters long with bell-shaped corollas. Growing 5 to 45 centimeters tall with ascending to erect stems that are stiff-glandular-hairy and generally branched at the base, it displays a delicate, open structure. Its leaves range 12 to 80 millimeters long, with oblong to ovate blades deeply lobed or compound, featuring toothed segments. The fruit is a small 3 to 4 millimeter spherical structure containing 2 to 4 pitted seeds.
Identification and appearance
Key characters: 25 sympatric species; distinguished by stiff glandular hairs and sepals with raised veins
Habitat and range
Habitat: Open clay flats
Elevation: 1000-1700 m
Outside California: to southeastern Oregon, Idaho
Bloom period
Phacelia thermalis blooms May-Aug.
How to tell it apart
vs Nemophila: Phacelia has flowers in coiled scorpion-tail clusters; Nemophila has solitary showy flowers at leaf axils.; vs Eucrypta: Phacelia is typically non-sticky with seeds that fall out cleanly; Eucrypta feels very sticky and retains 1-2 seeds in fruit.; vs Pholistoma: Phacelia has coiled flower clusters; Pholistoma has flowers scattered along stems with backward-pointing stem bristles.; vs Echium: Phacelia has coiled clusters of small flowers; Echium has large showy blue-purple flowers in tall spike-like clusters.; vs Gilia: Phacelia has coiled flower clusters and bristly foliage; Gilia has flowers in round heads or loose clusters with smoother foliage.
Frequently asked questions
Is Phacelia thermalis native to California?
Yes. Phacelia thermalis is native to California (recorded as native).
When does Phacelia thermalis bloom?
Phacelia thermalis blooms May-Aug.
What plant family does Phacelia thermalis belong to?
Phacelia thermalis is in the Hydrophyllaceae family, genus Phacelia.
What habitat does Phacelia thermalis grow in?
Phacelia thermalis grows in Open clay flats.
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.