Island Phacelia

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Island Phacelia

Phacelia insularis ssp. insularis

ListedJuly 31, 1997
FamilyHydrophyllaceae (Waterleaf)
DescriptionA herbaceous, annual wildflower with small lavender to violet, bell-shaped flowers.
HabitatCoastal grassland.
ThreatsHabitat degradation and direct consumption by introduced mammals, and competition with alien plants.


Phacelia insularis ssp. insularis (island Phacelia) was described in 1932 based on plants growing "on sand dunes at northeastern part of Santa Rosa Island." The new combination, Phacelia curvipes var. insularis, was published in 1943. After examining specimens from coastal northern California and determining their affinity to the island plants, the taxon was re-elevated to specific level in 1945, separating out the northern California plants as Phacelia insularis var. continentis, while leaving Phacelia insularis var. insularis to refer to the island plants. In 1951, the taxon was included in the description of Phacelia divaricata, a taxon common in southern California. A new combination Phacelia divaricata var. insularis was then published in 1959. It was then agreed that the interpretation of the taxon as Phacelia insularis var. insularis was valid treatment of the taxon.

Phacelia insularis ssp. insularis is a decumbent (reclining), branched annual of the waterleaf (Hydrophyllaceae) family. The short-hairy and glandular stems grow to 6 in (15 cm) high from a basal rosette of leaves. The small lavender to violet, bell-shaped flowers are borne in loose cymes. Phacelia insularis var. insularis can be distinguished from the other species of Phacelia on the islands based on the hastate leaf shape with basal lobes. The other Phacelia have pinnately divided or undivided but ovate leaves.


Phacelia insularis ssp. insularis is found within the island grassland community which is dominated by alien grasses, including slender wild oat (Avena barbata ), wild oat (Avena fatua ), ripgut (Bromus diandrus ), and soft chess (Bromus hordeaceus ), with scattered native bunchgrasses, shrubs, and herbs.


Phacelia insularis ssp. insularis occurs on Santa Rosa Island and San Miguel Island. Clifton Smith collected the species at Carrington Point on Santa Rosa Island in 1973, where Sarah Chaney also found the species in 1994. Thirty-one plants were reported from this site in subsequent surveys. On San Miguel Island, Phacelia insularis ssp. insularis was collected by Hoffmann in 1930 and by Munz in 1932. It was not collected again until 1978, when four populations were found. Drost relocated one of these sites on a bluff above Cuyler Harbor in 1984. National Parks Service staff has been watching without successs for the taxon on San Miguel Island. The population on Santa Rosa Island is currently the only known occurrence.


Phacelia insularis ssp. insularis is threatened by soil damage, competition with non-native grasses, and habitat alteration caused by cattle grazing, and elk and deer browsing.

Conservation and Recovery

The island Phacelia only survives as several tiny populations on Santa Rosa and San Miguel Islands. The broader habitat on these islands is being conserved in a relatively natural condition in the Channel Islands National Park, and by the Nature Conservancy, a private conservation organization. However, the island Phacelia and other rare plants are severely threatened by the feeding of introduced mammals. The protection of the endangered Phacelia requires that these herbivores be reduced or eliminated from its habitat. The abundance of invasive alien plants should also be reduced or eliminated, because they are providing intense competition to native species. The populations of the island Phacelia should be monitored, and research undertaken into its biology and habitat needs, including methods of management that would benefit the endangered plant. A captive-propagation program should be developed, to provide stock for out-planting to supplement the tiny natural population, and to reestablish additional populations in suitable habitat.


U.S. Fish and Wildlife Service
Ventura Fish and Wildlife Office
2493 Portola Road, Suite B
Ventura, California 93003
Telephone: (805) 644-1766;
facsimile (805) 644-3958

U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
Eastside Federal Complex
911 N. E. 11th Ave.
Portland, Oregon 97232-4181
(503) 231-6121


U.S. Fish and Wildlife Service. 31 July 1997. "Endangered and Threatened Wildlife and Plants; Final Rule for 13 Plant Taxa From the Northern Channel Islands, California." Federal Register 62 (147): 40954-40974