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Peirson's Milk-Vetch
(Astragalus magdalenae var. peirsonii )

Pierson's Milk-Vetch
BLM Photograph

Description: Perennial herb. Stems erect, 8-36 inches (2-9 decimeters) long. Leaf 1/2-6 inches (1-15 cm) long, with 3-13 leaflets. Leaflets narrow/oblong, 1/8-3/8 inches (2-8 millimeters) long, with one terminal leaflet. Inflorescence contains 5-20 flowers with pink- purple petals, often white tipped. Largest petal (banner) is 3/8-5/8 inches (10-14 millimeters) long. The fruit is a 6/8-1 3/8 inches (2-3.5 centimeters) long, and attached to the stem (sessile). The fruit is an oval pod with a small hook at the end, has stiff, straight, sharp hairs (strigose) covering it, is inflated (bladdery), and has only one chamber.

Distribution: The only known extant occurrences in the United States are in the Algodones (also known as Imperial) Sand Dunes of Imperial County.  It is also found on the sand dunes of the Gran Desierto of Sonora, Mexico.

Habitat: Found in desert dunes at elevation 55-250 meters.

Flowering Period: Blooms December-April

Similar Plants: The only other milk-vetch occurring in the Algodones Dunes is Borrego milk-vetch, Astragalus lentiginosus var. borreganus, which has non-inflated pods with two chambers.

Status: Federal Threatened, California State Endangered, California Native Plant Society List 1B

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Field Office: El Centro

Last updated: 08-05-2010