Astragalus australis var. olympicus

Common Names:
Cotton's milkvetch
Growth Habit:
CPC Number:
Profile Contributors:
Edward Guerrant, Ph.D.
Fully Sponsored

Reference Links

ITIS - Tropicos - USDA Plants - Fish & WildLife

Participating Institutions

The following Participating Institutions are custodians for this species in the CPC National Collection:
Rae Selling Berry Seed Bank & Plant Conservation Programs
University Of Washington Botanic Gardens

The conservation of Astragalus australis var. olympicus is fully sponsored.
Edward Guerrant, Ph.D. contributed to this Plant Profile.


Even though Astragalus australis var. olympicus is native only to high reaches in the Olympic Mountains of Washington, it is not immune to the impact that modern humans have had on the ecosystem. With an unfortunate lack of foresight, 12 mountain goats were introduced to the Olympic Mountains in the 1920s to provide animals for sport hunting. The original population of 12 has now grown to over 1,000 individuals. Mountain goats are not part of the native ecosystem in the Olympic Mountains, and consequently, the flora of the region is not adapted to the stresses that goats put on the plants. Astragalus australis var. olympicus is no exception.

While the Olympic Peninsula encompasses only 8% of Washingtons land, it contains 27% of the states rare flora. Olympic National Park has an even higher concentration of rare plants: 19% of the rare plants here are found in just over 2% of the state (Schreiner et al. 1994). This concentration of rare flora exists because small islands of habitat were not covered by ice or water during the last ice age. Mountain flora isolated in this habitat could not interbreed with other populations, and eventually evolved into its own distinct taxa.

Isolated high in the Olympic Mountains during the last ice age, this particular variety of A. australis evolved a unique trait: highly inflated seedpods. These seed pods have been likened to "mini greenhouses," increasing the temperature surrounding the developing seeds. This variety has not been isolated long enough to evolve into a separate species, but it is possible that this species will become distinct enough to become its own species if it continues to be isolated and cannot interbreed with other populations of A. australis (Schreiner et al. 1994).

Distribution & Occurrence


Conservation, Ecology & Research