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''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 thompsonii
/ref> 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 Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found els ...
to the
Wenatchee Mountains The Wenatchee Mountains are a range of mountains in central Washington State, United States of America. A major subrange of the Cascade Range, extending east from the Cascade crest, the Wenatchee Mountains separate the drainage basins of the ...
of the north-central Cascades in the US
State of Washington Washington (), officially the State of Washington, is a state in the Pacific Northwest region of the Western United States. Named for George Washington—the first U.S. president—the state was formed from the western part of the Washingto ...
. It grows in full sun and is strongly associated with rocky serpentine soils. Along with
Lomatium cuspidatum ''Lomatium cuspidatum'' (Wenatchee desertparsley) is a perennial herb of the family Apiaceae, native to the U.S. state of Washington. It is found primarily on open rocky slopes in the Wenatchee Mountains, strongly associated with serpentine sc ...
,
Oreocarya thompsonii ''Oreocarya thompsonii'' is a species of flowering plant in the genus '' Oreocarya'' with the common name Thompson's cryptantha (it was previously placed in the genus ''Cryptantha''). Description The leaves form a low basal rosette or cluster of ...
, and
Poa curtifolia ''Poa curtifolia'' is a species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any tw ...
, it is a strong indicator for serpentine in the area.


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 A pseudanthium (Greek for "false flower"; ) is an inflorescence that resembles a flower. The word is sometimes used for other structures that are neither a true flower nor a true inflorescence. Examples of pseudanthia include flower heads, compos ...
each containing white or pale
lavender ''Lavandula'' (common name lavender) is a genus of 47 known species of flowering plants in the mint family, Lamiaceae. It is native to the Old World and is found in Cape Verde and the Canary Islands, and from Europe across to northern and east ...
disc floret The family Asteraceae, alternatively Compositae, consists of over 32,000 known species of flowering plants in over 1,900 genera within the order Asterales. Commonly referred to as the aster, daisy, composite, or sunflower family, Compositae we ...
s but no
ray florets The family Asteraceae, alternatively Compositae, consists of over 32,000 known species of flowering plants in over 1,900 genera within the order Asterales. Commonly referred to as the aster, daisy, composite, or sunflower family, Compositae we ...
, with wooly (
tomentose Trichomes (); ) are fine outgrowths or appendages on plants, algae, lichens, and certain protists. They are of diverse structure and function. Examples are hairs, glandular hairs, scales, and papillae. A covering of any kind of hair on a plan ...
) flower stalks (peduncles) and floral bracts (involucre).Flora of North America, Thompson’s pincushion, ''Chaenactis thompsonii'' Cronquist
/ref> Leaves are sparsely woolly and singly
pinnate Pinnation (also called pennation) is the arrangement of feather-like or multi-divided features arising from both sides of a common axis. Pinnation occurs in biological morphology, in crystals, such as some forms of ice or metal crystals, an ...
with 2-5 pairs of generally flat entire lobes from multiple stems. The somewhat similar and much more widespread ''
Chaenactis douglasii ''Chaenactis douglasii'' is a North American species of flowering plant in the daisy family known by the common name Douglas' dustymaiden. Description ''Chaenactis douglasii'' is a variable herb, generally a perennial. It grows erect to , wit ...
'' 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''
{{Taxonbar, from=Q15572844 thompsonii Flora of Washington (state) Plants described in 1955 Taxa named by Arthur Cronquist