Flora of North America species comparison

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Chaenactis thompsonii

Chaenactis fremontii
Chaenactis thompsonii

Thompson's pincushion

desert pincushion, Fremont pincushion, Fremont's pincushion, pincushion flower
Habit Perennials, 10–30 cm (not or scarcely cespitose, not matted); proximal indument thinning with age, grayish, arachnoid-sericeous to thinly lanuginose. Plants 10–30(–40) cm; proximal indument glabrescent (early ± arachnoid, glabrous by flowering).
Stems

mostly 5–15+, ascending to erect.

mostly 1–12;

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, 1–7(–10) cm;

largest blades linear and terete or ± elliptic and plane, ± succulent, 0–1-pinnately lobed;

lobes 1–2(–5) pairs, remote, ± terete.
Peduncles

ascending to erect, 2–5 cm.

2–8(–10) cm, distally usually ± stipitate-glandular and, sometimes, ± arachnoid (at least early, often glabrescent by fruit).
Involucres

± obconic.

± hemispheric to obconic (bases pale and ± truncate in fruit).
Florets

corollas white to pinkish, 5–8 mm (inner);

peripheral corollas spreading, zygomorphic, enlarged.
Corollas

7–9 mm.

Phyllaries

longest (10–)12–15 mm;

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

longest 8–10(–12) mm;

outer usually glabrescent in fruit, apices erect, acute, ± rigid.
Heads

mostly 1–3 per stem.

(± radiant) mostly 1–5 per stem.
Cypselae

7–9 mm (eglandular);

pappi: longest scales 3.5–5 mm.

(3–)6–8 mm;

pappi of (1–)4(–5) scales in 1 series, longest scales 6–8.5 mm, lengths 1–1.3 times corollas (apices visible among corollas at flowering).
2n

= 10.

Chaenactis thompsonii

Chaenactis fremontii
Phenology Flowering Jun–Aug. Flowering Mar–May.
Habitat Rocky or gravelly serpentine slopes, scree, talus, openings in or above conifer forests Sandy or gravelly soils, warm deserts, often growing through shrubs
Elevation (900–)1200–2200 m ((3000–)3900–7200 ft) -10–1600 m (-0–5200 ft)
Distribution
from FNA
WA
[WildflowerSearch map]
[BONAP county map]
from FNA
AZ; CA; NV; UT; 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.)

Chaenactis fremontii is often the most abundant spring wildflower in the lower Mojave and northern Sonoran deserts, where it is reported to be a significant food source for desert tortoises (Gopherus agassizii Cooper). It also extends seaward into the southern San Joaquin Valley area of west-central California, often as hybrids with other taxa (see sectional discussion).

The involucre bases described above are characteristic of Chaenactis fremontii and can help separate it from some forms of C. stevioides.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 21, p. 407. FNA vol. 21, p. 414.
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. glabriuscula, C. macrantha, 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) A. Gray: Proc. Amer. Acad. Arts 19: 30. (1883)
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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