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Coulter's hibiscus, desert rose-mallow

pale face, paleface rose-mallow, rock hibiscus, rocl hibiscus

Habit Subshrubs, to 2 m, herbage with appressed-stellate and simple hairs throughout. Subshrubs, to 0.8 m, herbage densely ± yellowish stellate-tomentose throughout.
Stems

stellate hairs of younger stems dense, appressed, 4-armed, arms approximate in pairs, aligned with stem axis, lines of fine, curved hairs absent or obscured;

older growth grayish, rough, glabrescent.

older twigs yellowish brown, glabrescent, line of fine hairs obscured by other pubescence or absent.

Leaves

stipules linear-subulate, 3–10 mm;

petiole primarily in distal 1/2, sometimes themselves shallowly pinnately lobed, surfaces scabridulous, hairs appressed-stellate, obscure nectary present abaxially on midvein near base.

stipules narrowly triangular to subulate, 1–3 mm;

petiole to 1/2 as long as blade, adaxial fine, curved hairs absent or obscured by other pubescence;

blade oblong or broadly to narrowly ovate (often folded in pressed specimens), usually unlobed, rarely shallowly 3-angulate-lobate, mostly 1.2–3 × 1–2.5 cm, base cuneate to rounded or truncate, margins irregularly and coarsely dentate or dentate-crenate, apex broadly acute to truncate, surfaces stellate-tomentose, ± obscured nectary present abaxially on midvein near base.

Inflorescences

solitary flowers in axils of distal leaves.

solitary flowers in axils of distal leaves.

Pedicels

jointed below apices, to 17 cm, usually much exceeding subtending leaves;

involucellar bractlets 8–14, linear-subulate, 1–2 cm, margins ciliate.

obscurely joined below apex, 0.5–2 cm, equaling or exceeding subtending petioles;

involucellar bractlets 7–10, often absent, narrowly triangular to subulate, to 0.6 cm, margins not ciliate.

Flowers

erect or ascending;

calyx divided 3/4+ length, funnelform, 1.4–2.2 cm, equaling or slightly exceeding involucel, lobes narrowly lanceolate-triangular, margins ciliate, apices attenuate, nectaries absent;

corolla rotate, petals yellow to cream, usually with dark to obscure maroon lines basally, asymmetrically obovate to broadly obovate, 1.6–4 × 1–3.5 cm, margins ± entire, sparingly hairy abaxially where exposed in bud;

staminal column straight, yellow or cream, 0.6–1.4 cm, bearing filaments throughout, free portion of filaments not secund, 1–3 mm;

pollen yellow-orange;

styles cream, 1.5–5 mm;

stigmas maroon or cream.

ascending to erect;

calyx divided 2/3–4/5 length, funnelform, 0.7–1.6 cm, lobes narrowly triangular-ovate, apices acuminate, nectaries absent;

corolla rotate, petals pale purple or pink to nearly white, with maroon spot or lines basally, asymmetrically obovate, 1.3–3 × 0.9–2 cm, margins ± entire, finely hairy abaxially where exposed in bud;

staminal column straight, pink, 0.4–1.1 cm, bearing filaments throughout, free portion of filaments not secund, 1–3 mm;

pollen dark orange;

styles pale pink, 1.5–4 mm;

stigmas pale pink to maroon.

Capsules

pale olivaceous gray with darker median stripe on each valve, ovoid or ellipsoid, 0.7–1.7 cm, to 2/3 calyces, apex rounded, hairy near apex or glabrous throughout.

dull yellow-green with darker medial stripe on each valve, drying straw-colored, ovoid to subglobose, 0.6–1 cm, shorter than calyces, apex apiculate, glabrous or with minute hairs near apex and on sutures.

Seeds

dark brown, angulately reniform-ovoid, 2.4–3 mm, silky-hairy ± throughout.

dark brown, angulately reniform-ovoid, 2.2–3 mm, whitish, silky-hairy ± throughout, hairs 3–4 mm.

2n

= 22 (Mexico: Durango).

Hibiscus coulteri

Hibiscus denudatus

Phenology Flowering nearly year-round. Flowering year-round.
Habitat Desert, rocky slopes Desert, often rocky
Elevation 600–1600 m (2000–5200 ft) 30–1800 m (100–5900 ft)
Distribution
from FNA
AZ; NM; TX; Mexico (Baja California, Chihuahua, Coahuila, Durango, Nuevo León, Sonora, Zacatecas)
[WildflowerSearch map]
[BONAP county map]
from FNA
AZ; CA; NM; NV; TX; Mexico (Baja California, Baja California Sur, Chihuahua, Coahuila, Durango, Sonora)
[WildflowerSearch map]
[BONAP county map]
Discussion

Hibiscus coulteri has been recorded in the southern half of Arizona; in Otero County, New Mexico; and in the region west of the Pecos River in Texas.

A naturally occurring hybrid between Hibiscus coulteri and H. denudatus (Hibiscus ×sabei Weckesser) has recently been documented from western Texas (W. Weckesser 2011).

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

Hibiscus denudatus has been recorded from Imperial, Riverside, San Bernardino, and San Diego counties in southern California; from southernmost Nevada (southern Clark County); from the southern half and near the Grand Canyon in Arizona; from southwestern New Mexico; and from the region west of the Pecos River in Texas.

As noted in the previous species, a naturally occurring hybrid between Hibiscus denudatus and H. coulteri (Hibiscus ×sabei Weckesser) has recently been documented from western Texas (W. Weckesser 2011).

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

Source FNA vol. 6, p. 256. FNA vol. 6, p. 257.
Parent taxa Malvaceae > subfam. Malvoideae > Hibiscus Malvaceae > subfam. Malvoideae > Hibiscus
Sibling taxa
H. acetosella, H. aculeatus, H. biseptus, H. clypeatus, H. coccineus, H. dasycalyx, H. denudatus, H. furcellatus, H. grandiflorus, H. laevis, H. martianus, H. moscheutos, H. mutabilis, H. poeppigii, H. radiatus, H. rosa-sinensis, H. schizopetalus, H. striatus, H. syriacus, H. trionum
H. acetosella, H. aculeatus, H. biseptus, H. clypeatus, H. coccineus, H. coulteri, H. dasycalyx, H. furcellatus, H. grandiflorus, H. laevis, H. martianus, H. moscheutos, H. mutabilis, H. poeppigii, H. radiatus, H. rosa-sinensis, H. schizopetalus, H. striatus, H. syriacus, H. trionum
Name authority Harvey ex A. Gray: Smithsonian Contr. Knowl. 3(5): 23. (1852) Bentham: Bot. Voy. Sulphur, 7, plate 3. (1844)
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