Thelypodium howellii

Thelypodium howellii, the Howell's thelypody[1] or Howell's thelypodium, is a rare plant of the Western United States. It is endemic to a relatively small area on the borders of three western States: Oregon, Nevada, and California.

Thelypodium howellii
Thelypodium howellii spectabilis

Critically Imperiled  (NatureServe)
Scientific classification Edit this classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Rosids
Order: Brassicales
Family: Brassicaceae
Genus: Thelypodium
Species:
T. howellii
Binomial name
Thelypodium howellii

Description

The Thelypodium howellii plant is biennial. It is often somewhat hairy, especially near the base, but may be hairless and waxy in texture. It produces a slender, branching, erect stem up to 70 centimeters tall. The leaves are mostly located in a rosette around the base. Leaves located higher on the stem may have clasping bases.

The inflorescence is a raceme of widely spaced flowers with greenish white or purplish sepals and pale blue or purple, spoon-shaped petals. The fruit is a silique up to 4.5 centimeters long containing plump brown seeds.[2][3][4][5][6]

Subspecies
  • Thelypodium howellii subsp. howellii [7]
  • Thelypodium howellii subsp. spectabalis - Howell's spectacular thelypody.

Distribution, habitat, and ecology

This plant is endemic to a small area stretching from north-eastern Oregon to north-eastern California.[6] It lives in alkaline or adobe meadows and seeps, river valleys and moist plains in Great Basin sagebrush scrub.[2] The fire ecology of this plant is not known at present.

Conservation status and threats

U.S. Forest Service Pacific Southwest Region Sensitive Species.

California Native Plant Society List 1B.2.

NatureServe California State Rank: S2.2; Global Rank: G2

Oregon Department of Fish and Wildlife Endangered.

The Oregon Department of Fish and Wildlife's Conservation Strategy website reports that a large portion of this species' habitat has been converted to agricultural land, and its numbers are being limited by competition with invasive weeds, changes in hydrology, pressure from cattle grazing, and mowing in preparation for growing season.[8]

Field identification

Howell's thelypody flowers from May to July. Var. spectabilis, known only from Malheur Co., Oregon, is larger than var. howellii, has larger, more strongly purple flowers, and is a federally listed species.[6]

References
  1. USDA, NRCS (n.d.). "Thelypodium howellii". The PLANTS Database (plants.usda.gov). Greensboro, North Carolina: National Plant Data Team. Retrieved 9 December 2015.
  2. "Howell's Thelypodium". Eagle Lake Field Office. U.S. Department of Interior, Bureau of Land Management. Archived from the original on 2007-06-14. Retrieved 2007-05-01.
  3. Payson, Edwin Blake (1922). "Study of Thelypodium and its Immediate Allies". Annals of the Missouri Botanical Garden. 9 (3): 265–266. doi:10.2307/2990054. JSTOR 2990054.
  4. Schofield, W.B. (2002). Field Guide to the Liverwort Genera of Pacific North America. University of Washington Press. p. 181.
  5. Rollins, Reed C. (1993). Hickman, James C. (ed.). The Jepson Manual: Higher Plants of California. University of California Press. pp. 444–446.
  6. Hitchcock, C. Leo; Arthur Cronquist; Marion Ownbey; J. W. Thompson (1964). Vascular Plants of the Pacific Northwest, Part 2: Salicaceae to Saxifragaceae. University of Washington Press. p. 549.
  7. Jepson Manual treatment for Thelypodium howellii subsp. howellii
  8. "Howell's Spectacular Thelypody". Conservation Strategy. Oregon Department of Fish and Wildlife. Retrieved 19 July 2019.
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