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riverside spineflower, Xantus' spineflower

Howell's spineflower, Mendocino spineflower

Habit Plants erect to infrequently spreading, (0.3–)0.5–2.5(–3) × 0.5–3(–5) dm, thinly pubescent. Plants spreading or decumbent to somewhat erect, 0.3–1 × 1–5 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 or nearly so;

petiole 1–4 cm;

blade spatulate to broadly obovate, 1–3 × 0.5–1.5(–1.8) 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.

with secondary branches suppressed, greenish to grayish;

bracts 2, similar to proximal leaf blades only reduced, short-petiolate, becoming linear and aciculate at distal nodes, acerose, 1–5 cm × 5–15 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, greenish to grayish, broadly cylindric, not ventricose, 3–4 mm, with conspicuous, white, scarious margins between teeth and extending up awn, not corrugate, pubescent;

teeth spreading, equal, 0.5–1 mm, awns straight with longer ones 1–2 mm and anterior one mostly 2 mm, these 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 white and tepals white to rose, cylindric, (3–)3.5–4.5 mm, pubescent nearly throughout;

tepals connate 1/4 their length, dimorphic, oblong, truncate and erose to denticulate apically, those of outer lobes longer and wider than inner ones;

stamens 9, included;

filaments distinct, 3–4 mm, glabrous;

anthers pink to red, oblong, 0.6–0.8 mm.

Achenes

brown, lenticular, 4–4.5 mm.

light brown, globose-lenticular, 3–4.5 mm.

2n

= (72, 74, 76, 78), 80, (82, 84, 86, 88, 90).

Chorizanthe xanti

Chorizanthe howellii

Phenology Flowering May–Jul.
Habitat Sandy places in coastal dunes and grassland communities
Elevation 0-20 m (0-100 ft)
Distribution
from FNA
CA
[WildflowerSearch map]
[BONAP county map]
from FNA
CA
[BONAP county map]
Discussion

Varieties 2 (2 in the flora).

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

Of conservation concern.

Chorizanthe howellii is an octoploid probably derived from an ancient hybrid event involving C. cuspidata var. villosa and perhaps C. valida. It is known only from a dune area north of Fort Bragg in Mendocino County, and is federally listed as endangered.

(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. 456.
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. diffusa, C. douglasii, C. fimbriata, 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
Name authority S. Watson: Proc. Amer. Acad. Arts 12: 272. (1877) Goodman: Ann. Missouri Bot. Gard. 21: 44, plate 3, fig. 1. (1934)
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