(Map may reflect historical as well as recent sightings)
Howell's spectacular thelypody was federally listed as threatened
without critical habitat in 1999 (U.S. Fish and Wildlife Service
1999). A draft recovery plan is available for review (U.S. Fish
and Wildlife Service 2001).
Description and Life
Howell's spectacular thelypody is a biennial plant in the mustard
family (Brassicaceae). It grows to approximately 60 cm (24 in)
tall, with branches arising from near the base and arrowhead-shaped
leaves. The sepals are green, purple or lavender in color, and
the 4-petaled flowers are lavender to purple. Flowering typically
occurs from June through July. The petal shape and paired free
filaments distinguish T. howellii ssp. spectabilis from T. howellii
Howell's spectacular thelypody occurs in moist, moderately well-drained,
somewhat alkaline meadow habitats, typically growing with salt
tolerant species such as greasewood (Sarcobatus vermiculatus),
giant wild rye (Elymus cinereus), and goosefoot (Chenopodium spp.).
Howell's spectacular thelypody appears to be dependent on periodic
flooding because it rapidly colonizes areas adjacent to streams
that have flooded. The species occurs on soils in the Wingville,
Baldock and Haines Series (NRCS mapped soil unit STATSGO 179).
Reasons for Decline
The plant has been extirpated from about one-third
of known historic sites, including the type locality in Malheur
county. Threats to the taxon include 1) habitat loss due to urban
and agricultural development; 2) habitat degradation due to livestock
grazing and hydrological modification; 3) consumption by livestock;
4) use of herbicides or mowing during the growing season; and
5) competition with exotic species such as teasel (Dipsacus sylvestris),
bull thistle (Cirsium vulgare), Canada thistle (C. canadensis),
and yellow sweet clover (Melilotus officinalis).
This species occurs at 18 sites in the Baker-Powder River Valley
located in Union and Baker Counties, Oregon.