The Vascular Plant Flora of the South Puget Sound Prairies

Vascular plant species lists were compiled for all the major prairies that remain in south Puget Sound, Washington State, USA. Overall, 278 species were recorded in 15 prairies that ranged in area from 12-3,000 ha. Fifty-nine percent of these were native taxa, with forbs the most frequently represented life form (74%). Seventy percent of the species were perennials. Annuals were most common in Ft. Lewis prairies, which may reflect higher levels of disturbance. On average, introduced annuals outnumbered the native annuals 2:1. Twenty-three native species were widespread, occurring in >80% of the prairies; all but one of these were perennial. In contrast, 5 of the 18 most widespread non-natives were annuals. Forty percent (64) of the native species were found in only 1 or 2 prairies, and another 61 prairie species were documented from a variety of sources as formerly or currently growing in the south Puget Sound region, but not currently known from the 15 prairies we studied. Our results provide a basis for identifying species potentially appropriate for including in prairie restoration efforts in this region. Our findings also suggest taxa that are uncommon, rare, or locally extirpated, and which may only persist in this region if active efforts are made to establish them in extant sites.