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.Burke Herbarium Image Collection, Chaenactis thompsoniiBiota of North America Program 2014 county distribution mapHitchcock, 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. Hitchcock, C.L. and Cronquist, A. 2018. Flora of the Pacific Northwest, 2nd Edition, p. 556. University of Washington Press, Seattle.
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.Biota of North America Program 2014 county distribution map
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).Flora of North America, Thompson’s pincushion, Chaenactis thompsonii Cronquist Leaves are sparsely woolly and singly pinnate with 2-5 pairs of generally flat entire lobes from multiple stems. The somewhat similar and much more widespread Chaenactis douglasii usually has doubly pinnate leaves, produces much taller flowering stem, and does not grow in serpentine soils.
References
External links
Burke Museum of Natural History and Culture, University of Washington, Chaenactis thompsonii