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

knotweed spineflower

Habit Plants erect, 0.2–0.8(–1.5) × 0.1–0.7(–1) dm, pubescent. Plants prostrate, 0.1–0.5 × 0.3–2(–2.5) dm, villous.
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 0.5–1 cm;

blade oblanceolate to elliptic, 0.3–1 × 0.2–0.3 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 small clusters 0.5–1 cm across even at dichotomies, greenish or reddish;

bracts 2, petiolate or sessile, similar to proximal leaf blades, oblanceolate or narrowly elliptic to linear-lanceolate, 0.3–1 cm × 1–3 mm, awns absent.

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.

1, greenish or reddish, campanulate, 5–6-ribbed, 1.5–2.5 mm, corrugate, thinly pubescent;

teeth 5–6, unequal, 3 longer ones 1.5–3 mm, these alternating with 2 or 3 shorter ones 1–2 mm, anterior tooth not leaflike;

awns of prominent teeth uncinate and 1.5–3 mm, those of shorter teeth straight and 1–2 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.

1, included to slightly exserted;

perianth white to rose, cylindric, 1.5–1.8(–2) mm, densely pubescent abaxially;

tepals connate 2/3 their length, monomorphic, oblong, obtuse to truncate or minutely emarginate apically;

stamens (6) 9, slightly exserted;

filaments distinct, 0.8–1 mm, glabrous;

anthers reddish, ovate, 0.2–0.3 mm.

Achenes

brown, 3-gonous, (1.5–)1.8–2.2 mm.

dark brown to black, 3-gonous, 2–2.5 mm.

2n

= 38, 40.

Chorizanthe rigida

Chorizanthe polygonoides

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; nw Mexico
[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).

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

Key
1. Involucres 2-2.5 mm; awns of prominent involucral teeth 1.5-2 mm
var. polygonoides
1. Involucres 1.5-2 mm; awns of prominent involucral teeth 2-3 mm
var. longispina
Source FNA vol. 5, p. 467. FNA vol. 5, p. 466.
Parent taxa Polygonaceae > subfam. Eriogonoideae > Chorizanthe > subg. Amphietes > sect. Acanthogonum Polygonaceae > subfam. Eriogonoideae > Chorizanthe > subg. Amphietes > sect. Acanthogonum
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. 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. 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. polygonoides var. longispina, C. polygonoides var. polygonoides
Synonyms Acanthogonum rigidum
Name authority (Torrey) Torrey & A. Gray: Proc. Amer. Acad. Arts 8: 198. (1870) Torrey & A. Gray: Proc. Amer. Acad. Arts 8: 197. (1870)
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