|Listed||July 31, 1997|
|Description||A low-growing shrub with reddish, glandular stalks that support yellow-petaled flowers.|
|Habitat||Coastal chaparral, sage scrub, and pine forest.|
|Threats||Habitat degradation and feeding by introduced herbivorous mammals, changes in fire regime.|
Helianthemum greenei (island rush-rose) was described as Helianthemum greenei in 1895. The type locality was described as "a dry summit near the central part of the island of Santa Cruz." This nomenclature was retained in the most recent treatment for the genus.
Helianthemum greenei is a small shrub in the rock-rose (Cistaceae) family. The plant grows to 18 in (0.5 m) tall and has alternate leaves covered with star-shaped hairs. The reddish, glandular stalks support yellow-petaled flowers to 1 in (2.5 cm) wide. The fruit is a pointed capsule 0.25 in (0.6 cm) long. A more abundant species found on the islands, Helianthemum scoparium, is similar in appearance, but is not glandular-hairy and has greenish stalks and smaller fruits.
Helianthemum greenei is found in open and exposed areas in chaparral, coastal sage scrub, and island pine forest.
McMinn in 1951 and Thorne in 1967 reported seeing Helianthemum greenei on San Miguel Island, but no collections exist from that island in herbaria. Two collections of the plant were made from Santa Rosa Island by Epling and Erickson and Dunn in the 1930's, but no collections on Santa Rosa Island have been made since that time, despite recent surveys. Helianthemum greenei was reported from the northeast side of Black Jack Mountain on Santa Catalina Island by Thorne in 1966. No collections have been made at this locality, although a population of three individuals was recently reported from there. Habitat for the plant on Santa Catalina Island is being grazed by goats, mule deer, and bison, and is being rooted by pigs. In addition to the one population on Santa Catalina Island, Helianthemum greenei is currently known from 14 populations on Santa Cruz Island. In 1980, prior to sheep removal from the Nature Conservancy (TNC) lands on Santa Cruz Island, a study found that, of 10 populations, two had several dozen individuals, and six others has fewer than six individuals. Biologists have found strong evidence that the plant is eliminated by intense feral animal disturbance; the population recorded by Abrams and Wiggins in 1930 at Pelican Bay has not been relocated. The Biological Resources Division sponsored surveys in 1995 and 1996 reported 14 populations, 10 of which had nine as the mean number of plants and four had populations that ranged from 500 to 1,000. The number of individuals was clearly related to recent fire history with the 10 sites having few individuals being unburned, and four populations with a mean number of 663 having burned in 1994.
Helianthemum greenei is vulnerable to soil damage, altered fire frequencies and intensities, and rooting by feral pigs.
Conservation and Recovery
The island rush-rose may only survive as tiny populations on Santa Catalina Santa and Cruz Islands. The broader habitat on these islands is being conserved in a relatively natural condition in the Channel Islands National Park, and by TNC and Catalina Island Conservancy (these are private conservation organizations). However, the island rush-rose and other rare plants are severely threatened by the feeding of sheep, pigs, and other introduced mammals. The protection of the threatened rush-rose 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 rush-rose should be monitored, and research undertaken into its biology and habitat needs, including methods of management that would benefit the threatened 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. Reference U.S. Fish and Wildlife Service. 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 Contact U. S. Fish and Wildlife Service Ventura Fish and Wildlife Office 2493 Portola Road, Suite B Ventura, California 93003. Telephone: (805) 644-1766 Fax: (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 Telephone: (503) 231-6121 http://pacific.fws.gov/
U. S. Fish and Wildlife Service
Ventura Fish and Wildlife Office
2493 Portola Road, Suite B
Ventura, California 93003
Telephone: (805) 644-1766
Fax: (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
Telephone: (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