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riverside spineflower, Xantus' spineflower

diffuse spineflower

Habit Plants erect to infrequently spreading, (0.3–)0.5–2.5(–3) × 0.5–3(–5) dm, thinly pubescent. Plants spreading, decumbent, prostrate, or rarely slightly erect, 0.3–1(–1.5) × 0.5–2(–10) dm, villous.
Leaves

basal or nearly so;

petiole 1–2(–3) cm;

blade oblong or oblong-ovate to ovate, 0.3–1(–1.5) × 0.3–0.8(–1) cm, thinly pubescent adaxially, densely tomentose abaxially.

basal;

petiole 0.2–1.8(–2) cm;

blade oblanceolate, 0.3–2 × 0.1–0.4 cm, villous.

Inflorescences

mostly flat-topped and openly branched, usually reddish;

bracts persistent, 2, usually leaflike at proximal nodes and similar to proximal leaf blades only more reduced, short-petiolate, oblong-ovate to ovate, 0.3–0.8 cm × 2–6 mm, becoming sessile, reduced and scalelike at distal nodes, linear, acicular, often acerose, 0.1–0.4 cm × 0.5–1 mm, awns straight, 0.5–1 mm.

rather dense with secondary branches suppressed, white to greenish;

bracts 2, similar to leaf blades at proximal nodes only reduced, short-petiolate, becoming linear and aciculate at distal nodes, acerose, 0.3–2 cm × 1–4 mm, awns absent.

Involucres

in open clusters with 1 at node of dichotomies, reddish, cylindric, not ventricose, 3–4.5 mm, not corrugate, without scarious or membranous margins, thinly to densely pubescent;

teeth spreading, unequal, 0.7–1.5 mm, 3 longer ones more erect than 3 shorter and less-prominent ones;

awns uncinate, 0.5–1 mm.

1, mostly greenish, cylindric, not ventricose, 2–2.5 mm, with thin to broad and then conspicuous white or pinkish to purple, scarious margins extending nearly full length of awn, not corrugate, villous-hirsute;

teeth spreading to divergent, equal, 0.5–1 mm, awns uncinate with longer ones 1–2 mm, anterior one mostly 2 mm, alternating with shorter (0.5–1 mm) ones.

Flowers

long-exserted;

perianth rose to red, infrequently with white lobes, cylindric, 4.5–6 mm, pubescent;

tepals connate ca. 2/3 their length, monomorphic to slightly dimorphic, narrowly oblanceolate, rounded apically, those of outer whorl occasionally slightly broader and longer than those of inner whorl;

stamens 9, mostly included;

filaments distinct, 4–6 mm, glabrous;

anthers pink to red, oblong, 0.5–0.6 mm.

exserted;

perianth bicolored with floral tube lemon-yellow and tepals white, campanulate, 2.5–3 mm, glabrous;

tepals connate ca. 1/3 their length, monomorphic, oblong, acute to obtuse and entire apically;

stamens 3–9, slightly exserted;

filaments distinct, 1.5–2 mm, glabrous;

anthers yellow, oval, 0.3–0.4 mm.

Achenes

brown, lenticular, 4–4.5 mm.

dark brown, globose-lenticular, 2–2.5 mm.

2n

= 38, 40, 42.

Chorizanthe xanti

Chorizanthe diffusa

Phenology Flowering Apr–Jul.
Habitat Sandy to gravelly flats and slopes, coastal scrub communities, pine-oak woodlands
Elevation 30-800 m (100-2600 ft)
Distribution
from FNA
CA
[WildflowerSearch map]
[BONAP county map]
from FNA
CA
[WildflowerSearch map]
[BONAP county map]
Discussion

Varieties 2 (2 in the flora).

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

The involucral margins of Chorizanthe diffusa vary greatly. In some individuals, the white margins are barely visible. Plants with the margins of the involucre are predominantly white have been designated var. nivea. A full gradation between the extremes may be observed in most populations, although in coastal sands var. nivea is often the dominant expression. Diffuse spineflower occurs near the coast and in the Coast Ranges of central California.

Chorizanthe diffusa has been shown to inhibit carcinogen-induced preneoplastic lesions in a mouse mammary-organ culture model. This inhibitory activity is known to correlate with cancer chemopreventive effects in full-term models of tumorigenesis (see H. S. Chung et al. 1999).

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

Key
1. Involucres thinly pubescent
var. xanti
1. Involucres densely white-pubescent
var. leucotheca
Source FNA vol. 5, p. 463. FNA vol. 5, p. 452.
Parent taxa Polygonaceae > subfam. Eriogonoideae > Chorizanthe > subg. Amphietes > sect. Ptelosepala 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. rigida, C. robusta, C. spinosa, C. staticoides, C. stellulata, C. uniaristata, C. valida, C. ventricosa, C. watsonii, C. wheeleri
C. angustifolia, C. biloba, C. blakleyi, C. brevicornu, C. breweri, C. clevelandii, C. corrugata, C. cuspidata, 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. xanti var. leucotheca, C. xanti var. xanti
Synonyms C. andersonii, C. diffusa var. nivea, C. nivea, C. pungens var. diffusa, C. pungens var. nivea
Name authority S. Watson: Proc. Amer. Acad. Arts 12: 272. (1877) Bentham: in A. P. de Candolle and A. L. P. P. de Candolle, Prodr. 14: 26. (1856)
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