Clay Phacelia

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Clay Phacelia

Phacelia argillacea

ListedSeptember 28, 1978
FamilyHydrophyllaceae (Waterleaf)
DescriptionAnnual with blue to violet flowers.
HabitatPinyon-juniper woodlands and mountainbrush with shale substrate.
ThreatsAnimal grazing, poor reproduction.


Clay phacelia, Phacelia argillacea, is a winter annual, 4-14 in (10-35 cm) tall, with slightly hairy stems and blue to violet compound flowerheads. Seeds germinate in late summer or early autumn, stimulated by seasonal rainstorms. The first leaves are small, but by mid-October develop into rosettes from 0.4-2.8 in (1-7 cm) wide, which continue to grow slowly beneath the winter snow. After the snow melts and the temperature rises, the plant grows rapidly. By late May, the first flowers open and the plant continues blooming until late June or early July. Plant size varies, depending on the soil quality.


Clay phacelia grows in soils derived from Green River Shale in a pinyon-juniper and mountain brush area. Associated plants are yellow-flowered buckwheat and adventive houndstongue.


This species is apparently descended from a plant widely distributed over Colorado, Idaho, Wyoming, and Utah. Clay phacelia was isolated following climatic changes and became adapted to the local substrate and climate. The first collection of clay phacelia was from Pleasant Valley Junction, Utah, in 1883.

This plant is currently known from two locations in Utah: Pleasant Valley Junction near Colton Siding (Wasatch County); and Clear Creek near Soldier Summit (Utah County). Only a few plants of the Pleasant Valley Junction population survive. The Clear Creek population numbered about 200 plants in 1982.


Habitat alteration began in the 1880s when a railroad was built through the area, bisecting the Clear Creek population and destroying many plants. Years of maintenance work on the railroad right-of-way have taken their toll on remaining plants. In addition, grazing sheep eat or trample plants, and rock squirrels chew off the stems of young plants.

Conservation and Recovery

The goal of the U. S. Fish and Wildlife Service's Recovery Plan is to establish a self-sustaining population of 2,000-3,000 plants on at least a 120-acre (50-hectare) protected site. In the near term, the strategy is to use fences or wire mesh coverings to protect existing plants from animals, and to seek ways to stimulate plants to produce more seed.


U.S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
P.O. Box 25486
Denver Federal Center
Denver, Colorado 80225


Atwood, N. D. 1973. "Two New Species of Phacelia (Hydrophyllaceae)." Phytologia 26:437-438.

Atwood, N. D. 1975. "A Revision of the Phacelia crenulatae Group (Hydrophyllaceae) for North America." Great Basin Naturalist 35(2):127-190.

U.S. Fish and Wildlife Service. 1982. "Phacelia argillacea (Atwood) Recovery Plan." U. S. Fish and Wildlife Service, Albuquerque.

Welsh, S. L., et al. 1975. "Endangered, Threatened, Extinct, Endemic and Rare or Restricted Utah Vascular Plants." Great Basin Naturalist 35:327-376.