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Arizona rabbitbrush

pillar false gumweed, resinbush

Habit Shrubs, 8–20 cm; with woody, highly branched caudices, bark dark gray, highly fibrous with age. Shrubs, 40–120 cm; with woody, freely branched caudices (not readily differentiated from young shoots).
Stems

ascending, green, ± puberulent, stipitate-glandular.

green when young, soon becoming tan to white or grayish with age (bark of older stems flaky), branched, resinous when young, less so with age.

Leaves

erect to closely ascending;

sessile;

blades with ± evident midnerves, linear to narrowly elliptic, 7–20 × 0.7–1.5 mm, sulcate, sometimes apiculate, apices acute, faces moderately puberulent, uniformly stipitate-glandular.

ascending to spreading, becoming deflexed;

sessile;

blades with conspicuous midnerves plus 1–2 pairs of collaterals often evident, lanceolate to linear-elliptic, falcate, 6–35(–60) × 1–9 mm, often folded, margins sometimes undulate, apices acute, mucronate, ± spinulose, faces glabrous, ± gland-dotted, resinous.

Involucres

subcylindric, 9–11 × 2.5–3.5 mm.

hemispheric, 8–12 × 9–15 mm.

Disc florets

5;

corollas 5.5–7.5 mm, lobes 0.9–1.5 mm;

style branches 2.7–3.2 mm, appendages 1–1.7 mm.

30–40+;

corollas 6–8.5 mm, lobes 1–1.7 mm;

style branches 2.8–3.5, appendages 1.3–1.7 mm.

Phyllaries

± 20 in 4–5 series, in 4–5 strong vertical ranks, tan, often with green or dark subapical splotch, midnerves often obscure, linear or lanceolate to elliptic, 2–9 × 0.5–1.3 mm, unequal, outer ± herbaceous, inner chartaceous, strongly keeled, apices acute to rounded, tip cupped, faces of outer glabrous or puberulent.

40–60+ in 3–5 series, in spirals, mostly tan, ovate to lanceolate, unequal, 3–10 × 1–1.8 mm, greenish distally but scarcely herbaceous, apices acute or acuminate, often recurved, faces often glutinous.

Heads

in small cymiform to racemiform arrays.

usually in dense, cymiform arrays (to 7 cm wide), rarely borne singly, not overtopped by distal leaves.

Cypselae

tan, elliptic, 4.2–6 mm, mostly 5-ribbed, faces glabrous, sparsely glandular;

pappi tan, 6–7.5 mm.

tan, narrowly cylindric, 4–5 mm, glabrous or sparsely hairy, resinous;

pappi of 12–15, white or stramineous, lanceolate to lance-linear scales 2–4 mm.

2n

= 18.

= 18.

Chrysothamnus molestus

Chrysothamnus stylosus

Phenology Flowering late summer–fall. Flowering summer–fall.
Habitat Rocky soils, mostly on limestone pinyon-juniper woodland Canyonlands, dunes, in sandy soils, with 4-winged saltbush, ephedra, sand dropseed, blackbrush, and juniper
Elevation 1800–2400 m (5900–7900 ft) 1100–1700 m (3600–5600 ft)
Distribution
from FNA
AZ
[BONAP county map]
from FNA
AZ; UT
[WildflowerSearch map]
[BONAP county map]
Discussion

Chrysothamnus molestus is known only from Coconino County. It is in the Center for Plant Conservation’s National Collection of Endangered Plants.

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

Chrysothamnus stylosus has been treated previously in the monotypic genus Vanclevea.

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

Source FNA vol. 20, p. 190. FNA vol. 20, p. 190.
Parent taxa Asteraceae > tribe Astereae > Chrysothamnus Asteraceae > tribe Astereae > Chrysothamnus
Sibling taxa
C. depressus, C. eremobius, C. greenei, C. humilis, C. scopulorum, C. stylosus, C. vaseyi, C. viscidiflorus
C. depressus, C. eremobius, C. greenei, C. humilis, C. molestus, C. scopulorum, C. vaseyi, C. viscidiflorus
Synonyms C. viscidiflorus var. molestus Grindelia stylosa, Vanclevea stylosa
Name authority (S. F. Blake) L. C. Anderson: Madroño 17: 222. (1964) (Eastwood) Urbatsch: Sida 21: 1627. (2005)
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