Species Fact Sheet Willamette daisy Erigeron decumbens var. decumbens
STATUS: ENDANGERED CRITICAL HABITAT: DESIGNATED
Willamette daisy potentially occurs in these Oregon counties: Benton, Clackamas, Lane, Linn, Marion, Multnomah, Polk, Yamhill (Map may reflect historical as well as recent sightings)
The Willamette daisy was listed as endangered 2000. Critical
habitat was designated in 2006.
Description and Life
Willamette daisy is a perennial herb in the composite family
(Asteraceae) and can reach 15-62 cm (6-24 in) tall. Basal leaves
are 5-18 cm (2-7 in) long and less than 1.2 cm (0.5 in) wide,
becoming gradually shorter along the stem. The flowering stems,
which are taller than the vegetative stems, produce 2 to 5 flower
heads. The flowers are daisy-like, with yellow centers and 25-50
pinkish to blue rays, often fading to white with age. Flowering
typically occurs during June and early July.
This species occurs on alluvial soils (deposited by flowing waters).
The Willamette daisy occurs on soils in the Wapto, Bashaw and
Mcalpin Series (NRCS mapped soil unit STATSGO 81). The species
is known to have been extirpated (destroyed or no longer surviving)
from an additional 19 historic locations. Willamette daisy populations
are known mainly from bottomland but one population is found in
an upland prairie remnant.
Reasons for Decline
Prior to European settlement, prairie habitat was maintained
by fire, which prevented the establishment of woody species. Willamette
Valley prairie is considered to be among the rarest habitats in
western Oregon and is threatened by fragmentation, agriculture
and urban growth. Most sites are small and privately owned and
few sites are in protective ownership.
The Willamette Daisy is endemic to Oregon's Willamette Valley.
Historically, this plant was likely widespread throughout the
Valley. Currently, 18 sites are known, distributed over an area
of 700,000 hectares (1.7 million acres), between Grand Ronde and