Astragalus robbinsii var. jesupi
|Listed||June 5, 1987|
|Description||Perennial herb with featherlike compound leaves and a violet flower.|
|Habitat||Silt-filled cracks in calcareous bedrock along shaded river banks.|
|Threats||Hydroelectric projects, recreational activities.|
|Range||New Hampshire, Vermont|
Jesup's milk-vetch, Astragalus robbinsii var. jesupi, is a perennial herb with featherlike compound leaves; each oblong or elliptical leaflet is only 0.4-0.8 in (1-2 cm long. Several slightly hairy stems, 8-24 in (20-60 cm) tall, grow from a woody rhizome. Violet to bluish-purple flowers appear in late May or early June. The fruit is a flattened tapered pod. The form of the pod is important in differentiating among the three New England varieties of A. robbinsii. Of the other varieties, A. robbinsii var. robbinsii is now extinct, and var. minor is very rare in New England.
Jesup's milk-vetch prefers rocky bluffs along river banks, where it roots securely in silt-filled cracks of calcareous bedrock outcrops. Spring flooding annually scours the rock surfaces, ridding the milk-vetch of its competitor plants and depositing fertile soil. Shade provided by the mature hard-wood trees along the river bank is an important factor in the plant's survival.
This species is endemic to the central reaches of the Connecticut River Basin. This scenic stretch of river not only provides the essential habitat requirements for the milk-vetch but also shelters about 20 other rare plants and animals, including dwarf wedge mussel (Alasmidonta heterodon ) and the cobblestone tiger beetle (Cicindela marginipennis ).
Jesup's milk-vetch was first collected in 1877 at Sumner Falls in Plainfield, New Hampshire, and is currently known from three sites: the original collection site, now supporting less than 10 plants; a population of about 75 plants near Hartland (Windsor County), Vermont; and a vigorous colony of about 1,000 plants downstream near Claremont (Sullivan County), New Hampshire. The total known range of the milk-vetch extends along 16 mi (25 km) of the Connecticut River from Plainfield to Claremont.
In 1984, Jesup's milk-vetch was threatened by a proposed hydroelectric power project on the Connecticut River that would have inundated two of the three populations, including the largest. The Federal Energy Regulatory Commission (FERC) issued a permit to a private developer to study the feasibility of building a 20-megawatt dam. This dam project was eventually abandoned. A second developer, Connecticut River Hydro Partners, filed a similar permit application for a proposed dam at Chase Island, just upstream from the Claremont population of Jesup's milk-vetch.
Conservation and Recovery
Since this species was federally listed as Endangered in 1987, the FERC must consider the opinion of the U. S. Fish and Wildlife Service (FWS) before issuing further permits for any project that might disturb the habitat of Jesup's milk-vetch. FWS personnel are aware that protecting a short stretch of the river is not sufficient if large-scale upstream projects alter the flow of the river. The FWS opinion would also consider any project's impact on the Connecticut River Salmon Restoration Program, which is a high priority item on state and federal agendas.
Regional Office of Endangered Species
U.S. Fish and Wildlife Service
300 Westgate Center Dr.
Hadley, Massachusetts 01035
Countryman, W. D. 1978. "Rare and Endangered Vascular Plant Species in Vermont." U.S. Fish and Wildlife Service, Newton Corner, Massachusetts.
Crow, G. E. 1982. "New England's Rare, Threatened and Endangered Plants." U.S. Government Printing Office, Washington, D.C.
Storks, I. M., and G. E. Crow. 1978. "Rare and Endangered Vascular Plant Species in New Hampshire." U.S. Fish and Wildlife Service, Newton Corner, Massachusetts.
U.S. Fish and Wildlife Service. 1987. "Determination of Astragalus robbinsii var. jesupi (Jessup's milk-vetch) to be an Endangered Species." Federal Register 52 (108): 21481-21484.