Prairie Species Habitat Conservation Plan – Willamette Daisy
Erigeron decumbens var. decumbens
Willamette daisy was listed as endangered under the Federal Endangered Species Act in 2000 (more information). The species is also listed as endangered in the state of Oregon.
Willamette daisy is a small (15-60 cm tall) perennial forb in the sunflower family (Asteraceae). It has small, pale blue-lavender daisy-like flowers perched atop clusters of gray-green, grass-like leaves. Flowers are produced in June and July.
This species produces seeds in July and August, and can also spread vegetatively. The leaves of Willamette daisy appear similar to those of another member of the sunflower family, Hall's aster (Aster hallii).
The two species can usually be differentiated based on the color of their stems; Hall's aster has a reddish stem, while Willamette daisy does not.
Range and Habitat
This species is currently found only in the Willamette River Basin, and is primarily known to occur in Lane County, Oregon. Willamette daisy was thought to be extinct between 1934-1980, but is now known from approximately 30 sites in Benton, Lane, Linn, Marion and Polk Counties.
Willamette daisy lives in both wetland prairie and upland prairie or oak savanna, preferring sites with very little shrubby cover. It often occurs with tufted hairgrass (Deschampsia caespitosa), California oatgrass (Danthonia californica) and several species of rushes (Juncus).
Remaining populations of Willamette daisy are at risk from:
- Further habitat loss or fragmentation
- Invasion of prairie habitats by non-native species
- Encroachment of trees and shrubs into prairie habitats
- Elimination of natural disturbance regimes