|Listed||November 1, 1985|
|Description||Perennial herb with compound leaves, tiny leaflets, and orange flowers.|
|Habitat||Moderately disturbed blackland-prairie in hard clay soils.|
|Threats||Introduced plants; livestock grazing.|
Slender rush-pea (Hoffmannseggia tenella ) is a perennial with stems up to 6 in (15.2 cm) high. Leafstalks bear doubly compound leaves with five or six pairs of tiny oblong leaflets. These leaflets are only about 0.12 in (3 mm) in length. Stems terminate in three to five flowerbeds bearing clusters of orange flowers that bloom from March to June. The fruit is a seed pod that contains two to four seeds.
Four species of the genus Hoffmannseggia occur in Texas. One species—H. glauca —is common along west Texas roadsides.
Based on two known populations, slender rush-pea's natural habitat appears to be moderately disturbed or eroded segments of the Texas coastal prairie known as blackland-prairie. Other native plants associated with this habitat are little bluestem, buffalo grass, and Texas speargrass.
Slender rush-pea was first collected in 1931 near Corpus Christi in Nueces County, Texas. Thirty-three years later, it was discovered in neighboring Kleburg County. Neither of these historic sites appears to have survived.
A field survey in 1982 located one population containing three individual plants near Petronila Creek and State Highway 70 (Nueces County) in a gravel dump beside the highway. By 1985 the population at this site had risen to about 25 plants, most of which were on private property; in 1988, at the time of the publication of the "Slender Rush-Pea Recovery Plan," this population had doubled to 50 individuals. A second population of nearly 10,000 plants was discovered in 1985 in a rural cemetery in southern Nueces County.
Competing grasses, along with extensive grazing and cultivation, have destroyed much of the native plant system of the Texas coastal prairie. Suitable habitat for the slender rush-pea has been severely curtailed because non-native grasses, particularly King Ranch bluestem and Bermuda grass—both planted extensively for range improvement—have escaped into uncultivated areas, crowding out native grasses and forbs (herbs other than grasses). Non-native grasses readily invade blackland-prairie habitats after the dominant native grasses have been disturbed. Botanists have suggested that tilling or prescribed burning near the known populations might trigger germination of dormant slender rush-pea seeds. If, at the same time, introduced grasses are controlled, rush-pea populations should increase.
Conservation and Recovery
With only two surviving populations in Nueces County, slender rush-pea is extremely vulnerable and could be completely eliminated if the remaining habitat is modified. Habitat preservation, then, is the number one recovery priority. The U. S. Fish and Wildlife Service has sought the cooperation of local landowners to protect plants on their properties and is working with conservation groups to acquire or otherwise protect remaining habitat. Another element of the recovery strategy is to establish a cultivated population for research and reintroduction to the wild.
Maintaining the two known habitats requires 1) cooperative planning between private landowners and local government agencies, 2) facilitation of the Texas Highway Department's plans to protect plants near the highway, 3) ongoing monitoring of populations for human impact and disease, 4) searching for additional populations, 5) establishing a cultivated population, and 6) initiating studies to understand the ecology and population biology of the species.
Gould, F. W. 1975. "Texas Plants: A Checklist and Ecological Summary." Report. The Texas Agricultural Experiment Station, College Station.
Jones, F. B. 1982. Flora of the Texas Coastal Bend. 3rd ed. Rob and Bessie Welder Wildlife Foundation, Sinton, Texas.
Mahler, W. F. 1982. "Status Report on Hoffmannseggia tenella. " U. S. Fish and Wildlife Service, Office of Endangered Species, Albuquerque.
U. S. Fish and Wildlife Service. 1988. "Slender Rush-Pea (Hoffmannseggia tenella ) Recovery Plan." U. S. Fish and Wildlife Service, Albuquerque.