Chaenactis thompsonii

Chaenactis thompsonii is a North American species of flowering plants in the aster family known by the common name Thompson's pincushion and native to Washington State.[1][2][3][4][5]

Chaenactis thompsonii
Scientific classification Edit this classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Asterids
Order: Asterales
Family: Asteraceae
Genus: Chaenactis
Species:
C. thompsonii
Binomial name
Chaenactis thompsonii

Range and Habitat

Chaenactis thompsonii is endemic to the Wenatchee Mountains of the north-central Cascades in the US State of Washington. It grows in full sun and is strongly associated with rocky serpentine soils. Along with Lomatium cuspidatum, Oreocarya thompsonii, and Poa curtifolia, it is a strong indicator for serpentine in the area.[1][6][4]

Description

Chaenactis thompsonii is a perennial up to 30 cm (12 inches) tall, usually not forming extensive clumps or mats. Each vegetative branch may produce 1-3 flower heads each containing white or pale lavender disc florets but no ray florets, with wooly (tomentose) flower stalks (peduncles) and floral bracts (involucre).[1][4][7] Leaves are sparsely woolly and singly pinnate with 2-5 pairs of generally flat entire lobes from multiple stems.[1][4] The similar and much more widespread Chaenactis douglasii usually has doubly pinnate leaves and does not grow in serpentine soils.[4]

Chaenactis thompsonii flower
Chaenactis thompsonii leaves

References
  1. Burke Herbarium Image Collection, Chaenactis thompsonii
  2. Biota of North America Program 2014 county distribution map
  3. Hitchcock, C. L., A.J. Cronquist, F. M. Ownbey & J. W. Thompson. 1984. Compositae. Part V.: 1–343. In C. L. Hitchcock Vascular Plants of the Pacific Northwest. University of Washington Press, Seattle.
  4. Hitchcock, C.L. and Cronquist, A. 2018. Flora of the Pacific Northwest, 2nd Edition, p. 556. University of Washington Press, Seattle.
  5. "Chaenactis thompsonii". iNaturalist. Retrieved 2022-10-16.
  6. Biota of North America Program 2014 county distribution map
  7. Flora of North America, Thompson’s pincushion, Chaenactis thompsonii Cronquist
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