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rush bristleweed, rush-like bristleweed

Habit Subshrubs, 25–100 cm; caudices branched, taproots 2–10+ cm. Perennials, 2.5–14 cm; caudices branched; taproots 3–13+ cm.
Stems

3–15+, branched in distal 1/2, slender and wiry, glabrous.

8–30+, simple, moderately stout to stout, not wiry, villous to pilose.

Leaves

basal often withering by flowering, 20–35 × 6–12 mm, pinnatifid;

cauline evenly spaced, blades oblong to linear, scalelike, 4–6 × 1–2 mm (except proximalmost), markedly reduced distally, margins usually entire, faces glabrous.

basal persistent (similar to cauline);

cauline only a few pairs clustered with basal, absent distally, blades narrowly to broadly oblanceolate or spatulate, 10–80 × 3–10 mm, margins evenly to irregularly serrate or serrulate, teeth 3–14 per side, each tipped with white bristle 0.5–2 mm, faces sparsely to moderately hairy.

Peduncles

minutely glandular, if stipitate, then minutely so;

bracts 5–25, imbricate, grading into phyllaries.

moderately to densely white-puberulent, eglandular; ebracteate.

Heads

1.

Involucres

hemispheric (narrowed at bases), 0.5–0.8 × 1–1.2 cm.

depressed-hemispheric, 5–8 × 10–25 mm.

Ray florets

15–25;

corollas yellow, tubes 3.5–4 mm, laminae 5–6 × 1.5–2.5 mm.

20–35;

corollas pink to purple, tubes 2–3.5 mm, laminae 9.3–15 × 2.2–4.3 mm.

Disc florets

25–40+;

corollas 4.8–6.3 mm.

50–150+; 4.5–6.5 mm.

Phyllaries

in 5–6 series, oblong to linear-oblanceolate, 1.5–6.5 mm, apices acute, tipped by white bristle, faces minutely stipitate-glandular.

in 3–4 series, broadly linear to lanceolate, 2.5–13 mm, apices acute to acuminate, tipped by white seta, faces moderately puberulent.

Cypselae

narrowly obovoid to oblanceoloid, 1.5–2.5 mm, nerves 12–18, moderately tawny hairy;

pappi tawny, 3.5–6 mm, a few abaxial bristles to 1/3 of longest.

narrowly obovoid to oblong, 1.7–3 mm, weakly 10–20-nerved or -ribbed, moderately to densely covered with whitish to tawny hairs;

pappi whitish to tawny, 3.5–6 mm, a few abaxial bristles to 1/3 of longest.

2n

= 8, 16.

= 8, 16.

Xanthisma junceum

Xanthisma coloradoense

Phenology Flowering summer–fall. Flowering summer.
Habitat Rocky, dry slopes Volcanic ash deposits, gravelly soil, limestone outcrops, mountain summits and slopes, occasionally on plains
Elevation 100–1000 m [300–3300 ft] 2100–3700 m [6900–12100 ft]
Discussion

Xanthisma junceum is reported from Arizona, but no specimen has been seen; as it is coastal in distribution, the report is likely based on a misidentified specimen.

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

Xanthisma coloradoense is mostly alpine, but sometimes present in foothills or on plains, scattered through the southern Rocky Mountains of Colorado and southern Wyoming.

Xanthisma coloradoense and X. grindelioides var. grindelioides are known to hybridize in Carbon County, Wyoming, one of the few places where the two are sympatric. Several hybrid swarms have been detected in the vicinity of Wheatland Reservoir number 2.

Two varieties of Xanthisma coloradoense were recognized by R. L. Hartman (1976, 1990). They were distinguished by size, shape, and serration of leaves, size of flowering heads, and ray corolla length. With the number of additional collections amassed, these distinctions no longer hold and the varieties are not recognized.

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

Distribution
from FNA
CA; Mexico (Baja California, Sonora)
[WildflowerSearch map]
[BONAP county map]
from FNA
CO; WY
[BONAP county map]
Parent taxa Asteraceae > tribe Astereae > Xanthisma > sect. Sideranthus Asteraceae > tribe Astereae > Xanthisma > sect. Blepharodon
Sibling taxa
X. blephariphyllum, X. coloradoense, X. gracile, X. grindelioides, X. gypsophilum, X. spinulosum, X. texanum, X. viscidum
X. blephariphyllum, X. gracile, X. grindelioides, X. gypsophilum, X. junceum, X. spinulosum, X. texanum, X. viscidum
Synonyms Haplopappus junceus, Machaeranthera juncea Aster coloradoensis, Haplopappus coloradoensis, Machaeranthera coloradoensis, Machaeranthera coloradoensis var. brandegeei, Xylorhiza brandegeei
Name authority (Greene) D. R. Morgan & R. L. Hartman: Sida 20: 1406. (2003) (A. Gray) D. R. Morgan & R. L. Hartman: Sida 20: 1403. (2003)
Source Flora of North America vol. 20, p. 390. Flora of North America vol. 20, p. 387.
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