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devil's spineflower, rigid spineflower, rigid spiny-herb, spiny-herb

two lobed spineflower, twolobe spineflower

Habit Plants erect, 0.2–0.8(–1.5) × 0.1–0.7(–1) dm, pubescent. Plants erect or infrequently spreading, (0.5–)1–3(–4) × 1–3(–4) dm, pubescent.
Leaves

basal and cauline;

petiole 0.5–3(–4) cm;

basal blade broadly elliptic to obovate, 0.5–2.5 × (0.3–)0.5–2 cm, thinly pubescent adaxially, more densely so to tomentose abaxially;

proximal cauline leaf soon deciduous, 1, blade similar to basal leaf blades only 1–2(–2.5) × 0.5–1.5 cm, mucronate to awn-tipped, awn mostly 2–4 mm;

distal cauline leaf blade persistent, 1 per node, sessile, blade linear to linear-lanceolate, 0.1–1.5 × 0.05–0.15 cm, becoming hard and thornlike with age.

basal;

petiole 0.5–3 cm;

blade oblanceolate, 1–3(–5) × 0.4–1(–1.3) cm, thinly pubescent.

Inflorescences

with involucres in dense clusters in axils of bracts, these on short shoots and each subtended by cauline leaves;

bracts 2, subopposite to opposite, linear, 0.5–1(–1.2) cm × 1–2 mm, awns straight, 2–4 mm.

with involucres in open clusters 2–4(–6) cm diam., greenish or reddish to purplish;

bracts 2–3 at proximal node, usually leaflike, often with whorl of sessile bracts ca. midstem, elliptic, 0.5–1.5 cm × 2–6 mm, gradually becoming lanceolate to elliptic, 0.2–2 cm × 1.5–8 mm, at distal nodes scalelike, linear and aciculate, acerose, awns straight, 1–3 mm.

Involucres

1, greenish, urceolate, 3-ribbed, 2–3 mm, corrugate, pubescent, rarely villous near base in some;

teeth 3, unequal, with thickened anterior tooth toward base, 5–10 mm, sometimes expanding and becoming lanceolate to narrowly elliptic, others 0.5–1.2 mm;

awns straight.

3–10 or more, grayish or reddish, urceolate and slightly ventricose basally, 4–6 mm, without scarious or membranous margins, slightly corrugate, strigose;

teeth erect to spreading, unequal, 1–2 mm;

awns mostly uncinate, 0.5–2 mm, with longer anterior one straight, mostly 2 mm.

Flowers

1–2, included to slightly exserted;

perianth yellow, cylindric, 1.5–1.8 mm, densely pubescent abaxially;

tepals connate ca. 2/3 their length, monomorphic, oblong, rounded, entire apically;

stamens 9, slightly exserted;

filaments distinct, 0.5–1 mm, glabrous;

anthers yellowish, ovate, 0.2–0.3 mm.

exserted;

perianth bicolored with floral tube white to yellow and tepals red, maroon, or dark purple, cylindric, (4.5–)5–6 mm, sparsely pubescent;

tepals connate 1/2 their length, dimorphic, obovate, those of outer whorl spreading, slightly longer than those of inner whorl, 2-lobed, emarginate, or subacute apically, those of inner whorl erect, obtuse, fimbriate apically;

stamens 9, exserted;

filaments distinct, 4–5 mm, glabrous;

anthers yellow to golden, oblong, 1.2–1.8 mm.

Achenes

brown, 3-gonous, (1.5–)1.8–2.2 mm.

brown, globose-lenticular, 4–4.5 mm.

2n

= 38, 40.

= (34, 36, 38), 40, (42, 44, 46).

Chorizanthe rigida

Chorizanthe biloba

Phenology Flowering Feb–Jun.
Habitat Sandy to gravelly or rocky flats and slopes, desert scrub
Elevation -60-1900 m. (-200-6200 ft.)
Distribution
from FNA
AZ; CA; NV; UT; Mexico (Baja California, Sonora)
[WildflowerSearch map]
[BONAP county map]
from FNA
CA
[WildflowerSearch map]
[BONAP county map]
Discussion

Anyone with the misfortune to step bare-footed on Chorizanthe rigida after the plant has dried instantly appreciates its common name. The species is widespread on the Mojave and Sonoran deserts but only occasionally is it locally abundant or weedy. It is found also along the Lahontan Trough in western Nevada, a well-known biogeographic extension route north of the Mojave Desert (J. L. Reveal 1980). The exceedingly compact and dense inflorescences with suppressed secondary branches result in a series of leaves and bracts that subtend a closely arranged series of bracteated and involucrated flowers.

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

Varieties 2 (2 in the flora).

Unlike the serpentine species Chorizanthe palmeri and C. ventricosa, C. biloba occurs on gravelly or clayey soils. Those species and C. obovata can be quickly differentiated by carefully examining the colors, shapes, and modifications of the tepals. Immature specimens can be difficult to place, but a combination of geographic location and edaphic features can often enable accurate identification of even fragmentary material.

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

Key
1. Outer tepals deeply 2-lobed, occasionally erose apically
var. biloba
1. Outer tepals emarginate or subcordate apically
var. immemora
Source FNA vol. 5, p. 467. FNA vol. 5, p. 458.
Parent taxa Polygonaceae > subfam. Eriogonoideae > Chorizanthe > subg. Amphietes > sect. Acanthogonum Polygonaceae > subfam. Eriogonoideae > Chorizanthe > subg. Amphietes > sect. Ptelosepala
Sibling taxa
C. angustifolia, C. biloba, C. blakleyi, C. brevicornu, C. breweri, C. clevelandii, C. corrugata, C. cuspidata, C. diffusa, C. douglasii, C. fimbriata, C. howellii, C. leptotheca, C. membranacea, C. obovata, C. orcuttiana, C. palmeri, C. parryi, C. polygonoides, C. procumbens, C. pungens, C. rectispina, C. robusta, C. spinosa, C. staticoides, C. stellulata, C. uniaristata, C. valida, C. ventricosa, C. watsonii, C. wheeleri, C. xanti
C. angustifolia, C. blakleyi, C. brevicornu, C. breweri, C. clevelandii, C. corrugata, C. cuspidata, C. diffusa, C. douglasii, C. fimbriata, C. howellii, C. leptotheca, C. membranacea, C. obovata, C. orcuttiana, C. palmeri, C. parryi, C. polygonoides, C. procumbens, C. pungens, C. rectispina, C. rigida, C. robusta, C. spinosa, C. staticoides, C. stellulata, C. uniaristata, C. valida, C. ventricosa, C. watsonii, C. wheeleri, C. xanti
Subordinate taxa
C. biloba var. biloba, C. biloba var. immemora
Synonyms Acanthogonum rigidum C. palmeri var. biloba
Name authority (Torrey) Torrey & A. Gray: Proc. Amer. Acad. Arts 8: 198. (1870) Goodman: Ann. Missouri Bot. Gard. 21: 73. (1934)
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