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Texas madrone

Arizona madrone

Habit Shrubs or trees, 2–4(–8) m; bark brick red, peeling in smooth flakes over most larger limbs, retained on base of trunk on older specimens and eventually over most of oldest parts of plant, becoming gray, irregularly roughened (twigs of newly emerging shoots usually densely villous, often with mixture of glandular hairs, fully developed twigs hairy and/or glandular-hairy, or glabrate or glabrous, twig bark soon loosening and exfoliating, older twigs usually smooth, brick red or glaucous-grayish red). Trees, 3–8[–10] m; bark light gray to reddish gray, checkered with squarish to rectangular segments or plates, 1–4 × 1–2.5 cm, retained on bole and major limbs; twigs 3+ years old with brick-red outer bark exfoliating in flakes or, sometimes, in slender strips.
Leaves

± equal in size throughout;

petiole 1.2–2.5 cm, base slightly decurrent, glabrate;

blade green or slightly lighter green abaxially, pale or bright olive-green or glaucous-green, elliptic or slightly ovate-elliptic, (2.5–)4–6(–7.5) × (1.2–)1.8–3(–4) cm, base usually tapered, rarely slightly cordate, (margins smooth or irregularly toothed on sprouts), apex acute or obtuse, surfaces glabrous or ± hairy.

larger on sterile shoots with longer internodes;

petiole (often red), (1–)1.7–3.2(–4.2) cm, base slightly decurrent, glabrous;

blade slightly lighter green abaxially, olive-green and glossy adaxially, ovate, (2.5–)3–7.5(–9) × (1–)1.8–3(–4) cm, base usually tapered-acute, rarely slightly rounded [broader and more nearly ovate-lanceolate], apex usually acute, sometimes slightly acuminate, surfaces glabrous.

Inflorescences

(often showy), varying from densely clustered or openly-branched to relatively few-flowered;

axes hairy, with both glandular and eglandular hairs intermixed.

often congested;

axes densely hairy, hairs sometimes glandular.

Pedicels

accrescent, obliquely erect to pendulous, 1.6–3.2 mm, hairy, with both glandular and eglandular hairs intermixed;

bract (accrescent), clasping base, reddish or tan, scalelike, 1.3–2 mm (to 2.9–3 mm in fruit).

accrescent, obliquely erect or slightly pendulous, 2.4–5 mm (to 16 mm in fruit), densely hairy, hairs sometimes glandular;

bract clasping base, reddish, scalelike, 1.4–2 mm.

Flowers

calyx tan (sometimes with blush of pink), (1.8–3 mm), lobes 1–1.2 mm, apex obtuse or rounded;

corolla 5.1–5.4(–6.1) mm (the larger on rapidly developing, more open, and elongated inflorescences);

anthers ca. 1.5 mm, spurs 1/2–3/4 times length of thecae;

ovary with 2–3(–5) ovules per locule.

calyx pale green, lobes 1.1–1.5 mm (mostly hidden beneath corolla), apex obtuse or rounded;

corolla 5–5.6 mm;

anthers 1.3–1.5 mm, spurs 1/2–2/3 times length of thecae, (finely tuberculate);

ovary with (2–)3–5+ ovules per locule.

Berries

deep red or blackish red, 5.5–7.5 mm diam.

blackish red, 6.5–9 mm diam.

Seeds

2.5–3 mm.

ca. 2 mm.

2n

= 26.

Arbutus xalapensis

Arbutus arizonica

Phenology Flowering (Feb-)Mar–Apr(-May); ripe fruit appears after about 6 weeks. Flowering May–Jun(-Aug); fruiting Aug–Oct.
Habitat Rough, stony hills, mountain slopes, calcareous ledges Riverine forests and oak parklands along seasonally moist waterways
Elevation 300-2200 m (1000-7200 ft) 1500-2400 m (4900-7900 ft)
Distribution
from FNA
NM; TX; Mexico; Central America
[WildflowerSearch map]
[BONAP county map]
from FNA
AZ; NM; Mexico (Chihuahua, Durango, Jalisco, Sinaloa, Sonora, Zacatecas)
[WildflowerSearch map]
[BONAP county map]
Discussion

Arbutus xalapensis is frequent in the Edwards Plateau hill country southwest of Austin, Texas, where it is associated with junipers, oaks, and mesquite at moderate elevations. Westward, in the Chisos, Davis, and Guadalupe mountains, it occurs in the pinyon-juniper zone at higher elevations (to 2200 meters). In the Animas Mountains of Hidalgo County, southwestern New Mexico, A. xalapensis has limited contact with A. arizonica, and some herbarium specimens suggest that hybridization occurs there. Confirmation will require a more detailed analysis of those populations.

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

Two outstanding features of Arbutus arizonica distinguish it in the field: 1) the consistently narrow, glossy leaves with tapered leaf bases, and 2) the nonexfoliating bark that acquires a checkered appearance within a few years. Trees with the narrowest leaves overall and the most narrowly tapered bases occur in the populations in the extreme northern part of the range in Cochise, Graham, Pima, and Santa Cruz counties of southeastern Arizona and Hidalgo County in southwestern New Mexico.

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

Source FNA vol. 8, p. 400. FNA vol. 8, p. 399.
Parent taxa Ericaceae > subfam. Arbutoideae > Arbutus Ericaceae > subfam. Arbutoideae > Arbutus
Sibling taxa
A. arizonica, A. menziesii
A. menziesii, A. xalapensis
Synonyms A. texana, A. xalapensis var. texana A. xalapensis var. arizonica
Name authority Kunth: in A. von Humboldt et al., Nov. Gen. Sp. 3(fol.): 219 (A. Gray) Sargent: Gard. & Forest 4: 317. (1891)
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