Showy Indian Clover

Trifolium amoenum

Description

Showy Indian clover, Trifolium amoenum, a member of the pea family (Fabaceae or Leguminosae), is hairy, erect, and grows to a height of 4-27 in (10-68.5 cm). The leaves are pinnately compound, widely obovate, and 0.8-1.2 in (2-3 cm) long. The flowers, purple with white tips, are 0.5-0.6 in (1-1.5 cm) long and occur in dense, round or ovoid heads that are 0.8-1.2 in (2-3 cm) long.

Flowers appear from April to June. T. amoenum is similar in appearance to T. macraei, although it is generally larger and the flowers lack subtending bracts.

Habitat

Showy Indian clover has been found historically at elevations up to 1,020 ft (311 m) in a variety of habitats that include low wet swales, grasslands, and grassy hillsides.

Distribution

Showy Indian clover had a historical range extending west and north to Marin and Sonoma Counties from the western edge of the Sacramento Valley in Solano County.

The species was at one time widespread north and east of San Francisco Bay, but so many sites had been extirpated by urban and agricultural development that showy Indian clover was considered extinct because years of searching for it had not turned up a single sighting since 1969. This belief changed in 1993 when Peter Connors of the Bodega Marine Laboratory rediscovered a single showy Indian clover plant on private land in Sonoma County, a property now developed. Subsequent searches of this land in 1994 and 1995 found no showy Indian clover individuals. Another population of this species was discovered in 1996, consisting of about 200 plants growing on two residential lots in Marin County. One lot has a house on it, and a house is being built on the other; both landowners are currently cooperating in the conservation of the species on their property.

Showy Indian clover is a large, attractive plant that would most likely have been found if it still occurred in its historical localities.

Threats

Showy Indian clover has been extirpated from all 24 historical occurrences in seven counties; it is currently is known from one natural population of about 200 plants on two residential lots in Marin County. If this property is further developed or altered, it may no longer contain suitable habitat for showy Indian clover.

This species is threatened by loss of habitat from urbanization, land conversion to agriculture, competition with invasive plant species, livestock grazing, and destructive random events. Widespread urbanization continues at a rapid pace throughout the historic range. The respective populations of Sonoma and Marin Counties are expected to grow by 11.1% and 10.4% for the period 1996-2000. The extirpation of historical populations of this species may have been partially a result of competition with aggressive alien weeds.

A 1994 germination study of other Trifolium species from historical showy Indian clover habitat in Sonoma County suggested that some annual Trifolium species germinate in late November, well after the introduced species redstem storkbill (Erodium cicutarium ), ripgut brome (Bromus diandrus ), and California burclover (Medicago polymorpha ). By germinating and growing earlier, it is likely that alien species have reduced the numbers of showy Indian clover plants by occupying available space. This plant may have disappeared from some of its former locations due to grazing. Showy Indian clover is a large clover that blooms when many grassland plants have already turned brown, likely making it more attractive to grazing herbivores.

Most recent sightings of the plant were located outside of fences along roadsides, suggesting that the species survived for a period where it was protected from grazing.

Threats due to herbivory on the one natural population of this species are unknown, but livestock grazing is unlikely. Grazing would pose a threat to any undiscovered sites for the species. Although collection is not currently thought to be a threat to the species, the plant is large with showy flowers, and its populations are small enough that even limited collecting pressure would have harmful consequences. Any other occurrences of this species that may be discovered in the future might well attract collectors of plants and seed because showy Indian clover was once considered extinct.

Conservation and Recovery

Seed from cultivated showy Indian clover plants is currently being collected for future reintroduction efforts. In 1994, 18 plants were cultivated from half of the total seed crop produced by a single plant found the previous year. These plants were grown to produce seed for later reintroduction efforts. The other half of the seed that was recovered from the single individual was deposited for long-term storage at the U.S. Department of Agriculture National Seed Storage Laboratory in Fort Collins, Colorado. The seed is expected to be viable for decades.

Contact

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/

Reference

U. S. Fish and Wildlife Service. 22 October 1997. "Determination of Endangered Status for Nine Plants From the Grasslands or Mesic Areas of the Central Coast of California." Federal Register 62 (204): 54791-54808.