PRAIRIE BUSH CLOVER
Lespedeza Leptostachys
by
Jerry Selby, Director of Science and Stewardship
The Iowa Nature Conservancy

     Prairie bush clover ( Lespdeza leptostachya ), also known as the slender - leafed bush clover, is a federally threatened prairie plant endemic to the tallgrass prairie region of the upper Mississippi River Valley. It is found in only four midwestern states - Iowa, Illinois, Minnesota and Wisconsin. The "core" area for the species is on the Des Moines lobe of the Wisconsin glaciation in the Des Moines River and Little Sioux River basins, with populations concentrated in northwest Iowa and southwest Minnesota.  "Peripheral " populations are found in other parts of Iowa, Minnesota, Wisconsin and Illinois.
   
    Mature stems of prairie bush clover are generally 9 to 18 inches tall, but can be as tall as three feet. They are slender with widely spaced clover-like compound leaves with three leaflets, each about 1 inch long by 1/4 inch wide. The vegetation has a distinctive grayish-silver sheen. They bloom in mid-July with pale pink or cream-colored flowers arranged in open, branching flower heads to form elongated inflorescences. A characteristic feature of the genus Lespedeza is that individual plants produce two types of flowers: showy flowers that are open to pollinators (chasmogamous) and greatly reduced, closed and self-pollinating (cleistogamous) flowers.
   
    Prairie bush clover is a member of the pea family (Fabaceae), with 40 members of the genus Lespedeza worldwide and 12 species native to North America. Two native species have ranges that overlap with prairie bush clover. A familiar native species, widespread throughout its range, is round head bush clover (Lesoedeza capitata), which is similar in color, but with larger, wider leaves and tight flower heads forming globose inflorescences. Virginia bush clover (Lesoedeza virginica) overlaps with prairie bush clover in Illinois. It is more similar in general appearance, but has more densely packed flower heads, brighter pink flowers and more closely spaced leaves.

  As with other members of the pea family, the bush clovers play an important role in nitrogen fixing and both native and exotic species are important sources of fodder in southern states. Our native bush clovers are thus a potentially important source of climactically adapted genes.

   General habitat characteristics include well-drained dry to moderately moist (mesic) native prairies. It is a perennial plant that reproduces by seed often colonizing open habitats. Habitat characteristics of core populations are fairly consistent - primarily north facing, gentle slopes and fine silty loam, fine sandy loam or clay loam substrates. Peripheral populations are much more variable. Heavy reliance on self-fertilization in these geographically isolated populations could possibly explain the variability.

   Core populations tend to be much larger and dominated by seedling and juvenile plants, while peripheral populations are dominated by more mature flowering plants. 
It is unknown what serves as a limit to seedling germination or survival in these populations.

   Prairie bush clover was listed as federally threatened in February1987, and also is listed as threatened or endangered in each of the states in which it is found. Loss of habitat is given as the primary cause of its rarity, but unique life history characteristics probably also are factors. Preserves such as the Iowa Chapter's Freda Haffner Kettlehole protect about 40% percent of known sites.  Conservancy Botanist Bill Watson will be monitoring known populations of prairie bush clover to assess their status, and is conducting extensive surveys to identify new sites for this unique species. These surveys will play a key role in identifying priority sites for conservation.

I would like to thank Jerry Selby from The Iowa Nature Conservancy 
for letting me reprint this article in the Nature's Reading Room.