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NATURAL HISTORY

LANE MOUNTAIN MILK VETCH } Astragalus jaegerianus
FAMILY: Fabaceae

DESCRIPTION: The Lane Mountain milk vetch is a wispy perennial plant with a woody base, many branches, and weak stems that grow up to 20 inches long in a zigzag pattern. Its sparse leaves have between seven and 15 silvery leaflets that are each less than one inch long. Flowers range from clay colored to purple, with veins a shade darker. Seedpods, which have a partition dividing them into two cells, are pencil shaped and smooth.

HABITAT: The Lane Mountain milk vetch usually grows among host shrubs, occurs in granite-rich soils, and can be found on shallow, gravelly hummocks of coarse sand. These plants are found on very low ridges on bajadas, and they are thought to be highly dependent upon locally specific soil conditions.

RANGE: Only four populations of Lane Mountain milk vetch are known. All of these are found within California’s Mojave Desert north of Barstow, either adjacent to or contained within the Fort Irwin Military Reservation south of Death Valley National Park. The total range of the species is only 13 square miles in the vicinity of Paradise Range, Lane Mountain, and Coolgardie Mesa.

BREEDING: The drought-tolerant Lane Mountain milk-vetch flowers only with sufficient rainfall. When there is enough rain, the plants’ flowers bloom between April and June. They are pollinated by leaf-cutter, digger, and wool-carder bees. Repeated years of abundant reproduction have not been observed.

LIFE CYCLE: Individuals may live as long as 15 years. Though Lane Mountain milk vetch foliage dries up with the onset of the hot, dry summer, making the plant appear to be an annual, its taproot enables it to persist underground during unfavorable weather.

THREATS: The expansion of the U.S. Army’s Fort Irwin Military Reservation includes the majority of Lane Mountain milk vetch habitat, exposing plants to tank training and increased military activities. Additional threats include off-road vehicles, recreational gold mining, increasing wildfire frequency and fire-suppression activities, and military vehicles trespassing onto Bureau of Land Management lands.

POPULATION TREND: When the Lane Mountain milk vetch was listed under the Endangered Species Act, only 50 individuals were known. The U.S. Army has since performed field surveys, identifying approximately 5,000 individuals. More than half of these are found within the expansion area of the Fort Irwin Military Reservation. Recent studies indicate that despite plentiful rainfall in 2003 and 2005, little germination and establishment of new plants has occurred.

Photo by Mark Hessing, courtesy Wikimedia Commons