Flora of North America species comparison

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Chaenactis thompsonii

Chaenactis artemisiifolia
Chaenactis thompsonii

Thompson's pincushion

artemisia leaf chaenactis, white pincushion
Habit Perennials, 10–30 cm (not or scarcely cespitose, not matted); proximal indument thinning with age, grayish, arachnoid-sericeous to thinly lanuginose. Plants (15–)25–90(–200) cm.
Stems

mostly 5–15+, ascending to erect.

Leaves

mostly cauline, 2–5 cm;

largest blades ± elliptic, ± plane, 1-pinnately lobed;

lobes mostly 2–5 pairs, remote, ± plane.

basal (withering) and cauline, 3–15(–20) cm;

largest blades ± plane, not succulent;

primary lobes mostly 5–10 pairs, ultimate lobes ± crowded, antrorse, lanceolate to elliptic, plane.
Peduncles

ascending to erect, 2–5 cm.

1.5–6 cm.
Involucres

± obconic.

± hemispheric, mostly 10–15 mm diam.
Receptacles

paleae 0.
Corollas

7–9 mm.

5–7 mm.
Phyllaries

longest (10–)12–15 mm;

outer closely lanuginose, not stipitate-glandular, apices erect, ± rigid.

longest 7–10(–12) mm, ± densely villous, not or sparsely glandular;

apices (all) erect, ± green, acute or scarcely acuminate, not aristate, ± plane.
Heads

mostly 1–3 per stem.

Cypselae

7–9 mm (eglandular);

pappi: longest scales 3.5–5 mm.

compressed, 4–7 mm;

pappi 0 or coroniform (of ± 10 scales, longest 0.1–0.5 mm).
2n

= 16.

Chaenactis thompsonii

Chaenactis artemisiifolia
Phenology Flowering Jun–Aug. Flowering Apr–early Jul.
Habitat Rocky or gravelly serpentine slopes, scree, talus, openings in or above conifer forests Dry canyons, open slopes, often over granitoid rocks, locally abundant in chaparral burns or other recovering disturbances
Elevation (900–)1200–2200 m ((3000–)3900–7200 ft) 80–1600 m (300–5200 ft)
Distribution
from FNA
WA
[WildflowerSearch map]
[BONAP county map]
from FNA
CA; Mexico (Baja California)
[WildflowerSearch map]
[BONAP county map]
Discussion

Of conservation concern.

Chaenactis thompsonii appears to be sister to C. evermannii; it is known from the mountains of central and northwestern Washington. The similar habits of C. thompsonii and C. ramosa (= C. douglasii var. douglasii) appear to result from convergent evolution in the distinctive habitat of their type localities (Wenatchee Mountains), not from a close genetic relationship as suggested by Cronquist.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

In the flora area, Chaenactis artemisiifolia is known from the Transverse and Peninsular ranges and seaward valleys of southwestern California. It is fire-adapted; its germination is significantly enhanced by exposure to biomass smoke (J. E. Keeley and C. J. Fotheringham 1998).

Chaenactis lacera Greene, the eighteenth species of the genus, is known from coastal portions (including islands) of the western Vizcaíno Desert in Baja California and Baja California Sur, Mexico. Forms of C. artemisiifolia sometimes resemble C. lacera in coastal southern California (P. Stockwell 1940), where C. lacera could eventually be introduced. Besides the key characteristics above, C. lacera differs from C. artemisiifolia by its largest leaf blades broadly ± elliptic, 2–3-pinnately lobed, ultimate lobes remote, recurved to retrorse, ± linear, involute (leaf blades appearing ± skeletal).

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 21, p. 407. FNA vol. 21, p. 402.
Parent taxa Asteraceae > tribe Heliantheae > subtribe Chaenactidinae > Chaenactis > sect. Macrocarphus Asteraceae > tribe Heliantheae > subtribe Chaenactidinae > Chaenactis > sect. Acarphaea
Sibling taxa
C. alpigena, C. artemisiifolia, C. carphoclinia, C. cusickii, C. douglasii, C. evermannii, C. fremontii, C. glabriuscula, C. macrantha, C. nevadensis, C. nevii, C. parishii, C. santolinoides, C. stevioides, C. suffrutescens, C. xantiana
C. alpigena, C. carphoclinia, C. cusickii, C. douglasii, C. evermannii, C. fremontii, C. glabriuscula, C. macrantha, C. nevadensis, C. nevii, C. parishii, C. santolinoides, C. stevioides, C. suffrutescens, C. thompsonii, C. xantiana
Synonyms Acarphaea artemisiifolia
Name authority Cronquist: in C. L. Hitchcock et al., Vasc. Pl. Pacif. N.W. 5: 123, fig. [p. 125]. (1955) (Harvey & A. Gray) A. Gray: Proc. Amer. Acad. Arts 10: 74. (1874)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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