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Phacelia thermalis

Greene

Hot Springs Phacelia

G3Vulnerable (G3G4) Found in 1 roadless area NatureServe Explorer →
G3VulnerableGlobal Rank
UnknownThreat Impact
Identity
Unique IDELEMENT_GLOBAL.2.137707
Element CodePDHYD0C4L0
Record TypeSPECIES
ClassificationSpecies
Classification StatusStandard
Name CategoryVascular Plant
Endemicendemic to a single nation
KingdomPlantae
PhylumAnthophyta
ClassDicotyledoneae
OrderSolanales
FamilyHydrophyllaceae
GenusPhacelia
Other Common Names
Heated Phacelia (EN) heated phacelia (EN) Hot Springs Scorpionweed (EN) Phacélie des eaux thermales (FR)
Concept Reference
Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR.
Conservation Status
Rank Method Rank calculation - Biotics v2
Review Date2026-03-13
Change Date1988-05-16
Edition Date2026-03-13
Edition AuthorsHeidel, B. (1999), rev. K. McConnell (2001), rev. Soteropoulos (2026)
Threat ImpactUnknown
Range Extent200,000-2,500,000 square km (about 80,000-1,000,000 square miles)
Number of Occurrences6 - 80
Rank Reasons
Phacelia thermalis is an annual herb found in open, sparsely vegetated areas, including clay flats, sagebrush scrub, open forests and juniper or Douglas fir woodlands. It is endemic to the northwestern United States from southwestern Idaho, southeastern Oregon, northeastern California, and northwestern Nevada, disjunct in northeastern Montana; it is introduced in Saskatchewan, Canada. There are at least sixteen occurrences, which face threats from development, road construction and maintenance, and competition from nonnative plants. Monitoring of populations should be conducted to improve our understanding of reproduction, plant abundance, threats, and trends, as well as continuing conservation measures to protect the taxon.
Range Extent Comments
Phacelia thermalis is endemic to the northwestern United States from southwestern Idaho, southeastern Oregon, northeastern California, and northwestern Nevada, disjunct in northeastern Montana (Idaho Fish and Game 2026, Jepson Flora Project 2026, MTNHP 2026, OSU 2026); it is introduced in Saskatchewan, Canada (Scoggan 1978). Range extent was estimated to be over 200,000 square kilometers using herbarium specimens, photo-based observations, and NatureServe Network occurrence data documented between 1994 and 2025 (RARECAT 2025, GBIF 2026, iNaturalist 2026, NatureServe 2026, SEINet 2026).
Occurrences Comments
By applying a 1 km separation distance to herbarium specimens, photo-based observations, and NatureServe Network occurrence data documented between 1994 and 2025, it is estimated that there sixteen occurrences rangewide (RARECAT 2025, GBIF 2026, iNaturalist 2026, NatureServe 2026, SEINet 2026).
Threat Impact Comments
This species is threatened by development, road construction and maintenance, and competition from nonnative plants, though there is insufficient data, including anecdotal accounts, to understand scope and severity of threats for this species rangewide (Montana Field Guides 2026, NatureServe 2026).
Ecology & Habitat

Description

Hot Spring Phacelia is an annual that is branched from the base. It has prostrate or ascending stems. The alternate leaves have broadly lance-shaped blades that are 1-9 cm long with toothed and deeply lobed margins and well-developed petioles. Foliage is glandular-hairy. The short-stalked flowers are borne in crowded, narrow, 1-sided, curved spikes that are up to 10 cm long. The spikes unwind as they mature and originate in the leaf axils. The lavendar to whitish flowers each have a 5-lobed tubular corolla that is 3-4 mm long and 5 narrowly lance-shaped, hairy sepals that are as long as the corolla in flower but twice as long in fruit. The stamens are included in the corolla tube. The fruit is a capsule with 2-4 seeds.

Diagnostic Characteristics

PHACELIA IVESIANA has strap-shaped sepals and is not as densely glandular-hairy. P. LUTEA has yellow flowers and only shallowly lobed leaves.

Habitat

Phacelia thermalis grows on open, sparsely vegetated areas, including clay flats, sagebrush scrub, open forests and juniper or Douglas fir woodlands (CalFlora 2026, Jepson Flora Project 2026, MTNHP 2026).

Reproduction

This taxon flowers from May to August (Jepson Flora Project 2026).
Terrestrial Habitats
Woodland - ConiferShrubland/chaparralGrassland/herbaceousBarrens
Other Nations (2)
CanadaNNA
ProvinceRankNative
SaskatchewanSNANo
United StatesN3
ProvinceRankNative
CaliforniaSNRYes
MontanaS2Yes
OregonSNRYes
NevadaSUYes
IdahoS1Yes
Threat Assessments
ThreatScopeSeverityTiming
1 - Residential & commercial developmentUnknownUnknownHigh (continuing)
4 - Transportation & service corridorsUnknownUnknownHigh (continuing)
4.1 - Roads & railroadsUnknownUnknownHigh (continuing)
8 - Invasive & other problematic species, genes & diseasesUnknownUnknownHigh (continuing)
8.1 - Invasive non-native/alien species/diseasesUnknownUnknownHigh (continuing)
8.1.1 - Unspecified speciesUnknownUnknownHigh (continuing)

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Plant Characteristics
DurationANNUAL
Economic Value (Genus)No
Roadless Areas (1)
California (1)
AreaForestAcres
Hat Mtn.Modoc National Forest9,478
References (13)
  1. CalFlora. 2026. Information on California plants for education, research and conservation. Berkeley, California: The CalFlora Database [web application]. Available: http://www.calflora.org/. (Accessed 2026).
  2. Global Biodiversity Information Facility (GBIF). 2026. Global Biodiversity Information Facility (GBIF) data portal. Online. Available: https://www.gbif.org/ (accessed 2026).
  3. Heidel, B. L. 1994. Sensitive plant species survey in Garfield and McCone counties, Montana. Unpublished report to the Bureau of Land Management. Montana Natural Heritage Program, Helena, Montana. 58 pp. plus appendices.
  4. Idaho Department of Fish and Game (IDFG). 2026. Idaho Species Diversity Database. Online. Available: https://idfg.idaho.gov/species/taxa.
  5. iNaturalist. 2026. Online. Available: https://www.inaturalist.org (accessed 2026).
  6. Jepson Flora Project (eds.) 2026. Jepson eFlora. Online. Available: https://ucjeps.berkeley.edu/eflora/ (accessed 2026).
  7. Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR.
  8. Montana Natural Heritage Program (MTNHP). 2026. Montana Field Guide. Online. Available: http://fieldguide.mt.gov (Accessed 2026).
  9. NatureServe. 2026. NatureServe Network Biodiversity Location Data. NatureServe, Arlington, Virginia.
  10. Oregon State University (OSU). 2026. Oregon Flora website. Oregon State University Herbarium at Oregon State University. Online. Available: https://oregonflora.org/ (accessed 2026).
  11. <p>NatureServe's Rapid Analysis of Rarity and Endangerment Conservation Assessment Tool (RARECAT). 2025. Version: 2.1.1 (released April 04, 2025).</p>
  12. Scoggan, H.J. 1978-1979. The flora of Canada: Parts 1-4. National Museums Canada, Ottawa. 1711 pp.
  13. Southwest Environmental Information Network (SEINet). 2026. Collections Databases. Online. Available: https://swbiodiversity.org/seinet/collections/index.php (accessed 2026).