Flora of North America species comparison

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Chaenactis thompsonii

Chaenactis macrantha
Chaenactis thompsonii

Thompson's pincushion

big-head dusty maidens, bighead dustymaiden, large-flower chaenactis, Mohave pincushion, Mojave pincushion, showy dustymaidens
Habit Perennials, 10–30 cm (not or scarcely cespitose, not matted); proximal indument thinning with age, grayish, arachnoid-sericeous to thinly lanuginose. Plants 5–25(–35) cm; proximal indument grayish, arachnoid-sericeous to closely lanuginose (sometimes tardily glabrescent).
Stems

mostly 5–15+, ascending to erect.

mostly 1–5;

branches mainly proximal.
Leaves

mostly cauline, 2–5 cm;

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

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

basal (withering) and cauline, 1.5–7 cm;

largest blades ± elliptic to ovate, ± plane, not succulent, 1(–2)-pinnately lobed (± gland-dotted beneath indument);

primary lobes mostly 2–5 pairs, ± remote, ultimate lobes ± plane.
Peduncles

ascending to erect, 2–5 cm.

1.5–8 cm, arachnoid-sericeous to thinly lanuginose distally, not stipitate-glandular.
Involucres

± obconic.

± obconic to broadly cylindric.
Florets

corollas (nocturnal) white to pinkish or cream, 9–12(–15) mm (lengths 1.8–2.2 times cypselae; anthers ± included);

peripheral corollas nocturnally spreading, actinomorphic, scarcely enlarged.
Corollas

7–9 mm.

Phyllaries

longest (10–)12–15 mm;

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

longest 12–18 mm;

outer arachnoid-sericeous to thinly lanuginose in fruit, not stipitate-glandular, apices ± squarrose, blunt, pliant.
Heads

mostly 1–3 per stem.

(± radiant, nocturnally), mostly 1–5(–7) per stem (nodding in bud).
Cypselae

7–9 mm (eglandular);

pappi: longest scales 3.5–5 mm.

5–6(–7) mm;

pappi of 8 scales in 2, abruptly unequal series, longest scales 5–7 mm.
2n

= 12.

Chaenactis thompsonii

Chaenactis macrantha
Phenology Flowering Jun–Aug. Flowering Mar–early Jul.
Habitat Rocky or gravelly serpentine slopes, scree, talus, openings in or above conifer forests Open, loose, light-colored, silty, usually calcareous or alkaline, desert soils, often covered by or mixed with gravel
Elevation (900–)1200–2200 m [(3000–)3900–7200 ft] 600–2200 m [2000–7200 ft]
Distribution
map from FNA
WA
[WildflowerSearch map]
[BONAP county map]
map from FNA
AZ; CA; ID; NV; OR; UT
[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.)

Though the derived floral features of Chaenactis macrantha obscure its relationships, it may represent a link between sect. Chaenactis (annuals; pappus scales in regular, often strongly reduced series) and sect. Macrocarphus (leaf blades gland-dotted). Resemblance of its heads, leaves, and indument to those of C. thompsonii and relatives is striking. It appears to form no natural hybrids, perhaps because of its nocturnal corollas.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Parent taxa Asteraceae > tribe Heliantheae > subtribe Chaenactidinae > Chaenactis > sect. Macrocarphus Asteraceae > tribe Heliantheae > subtribe Chaenactidinae > Chaenactis > sect. Chaenactis
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. artemisiifolia, C. carphoclinia, C. cusickii, C. douglasii, C. evermannii, C. fremontii, C. glabriuscula, C. nevadensis, C. nevii, C. parishii, C. santolinoides, C. stevioides, C. suffrutescens, C. thompsonii, C. xantiana
Name authority Cronquist: in C. L. Hitchcock et al., Vasc. Pl. Pacif. N.W. 5: 123, fig. [p. 125]. (1955) D. C. Eaton: in S. Watson, Botany (Fortieth Parallel), 171, plate 18, figs. 1–5. (1871)
Source FNA vol. 21, p. 407. Treatment author: James D. Morefield. FNA vol. 21, p. 410. Treatment author: James D. Morefield.
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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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