Quercus arizonica |
Quercus phellos |
|
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Arizona oak, Arizona white oak |
willow oak |
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Habit | Trees, evergreen or subevergreen, small to moderate-sized trees, rarely to 18 m. Bark scaly. | Trees, deciduous, to 30 m. Bark dark gray and smooth, becoming darker and irregularly fissured with age, inner bark light orange. |
Twigs | yellowish, 1.5-2.5 mm diam., persistently felty-tomentose, eventually dingy gray. |
reddish brown, 1-2 mm diam., glabrous. |
Buds | dull russet-brown, ovoid, distally subacute or rounded, 3 mm, sparsely pubescent or glabrate. |
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Leaves | blade elliptic or oblong to narrowly obovate or oblanceolate, planar or moderately convex, to (30-)40-80(-90) × 15-30 mm, thick and leathery, usually stiff, base cordate or rounded and weakly cordate, margins entire or coarsely toothed especially near apex, cartilaginously revolute, teeth mucronate-tipped, obscure or prominent, secondary veins ca. 7-11 on each side, branching, passing into teeth when present, apex acute to usually obtuse or broadly rounded; surfaces abaxially dull, sparsely pubescent or subtomentose with curly branched hairs, reticulate from prominent, raised secondary veins, usually glaucous where exposed, adaxially dark or bluish green, moderately lustrous, sparsely and minutely stellate-pubescent, secondary veins slightly raised or prominent within depressions or impressed. |
blade linear to narrowly elliptic, usually widest near middle, 50-120 × 10-25 mm, base acute, margins entire with 1 apical awn, apex acute; surfaces abaxially pale green, glabrous, rarely softly pubescent, adaxially light green, glabrous. |
Acorns | solitary or paired, subsessile, occasionally on peduncle to 15 mm; cup hemispheric or cup-shaped, 5-10(-15) mm deep × 10-15 mm wide, enclosing ca. 1/2 nut, base rounded, margin rather coarse, scales cream to brown, broadly ovate, evenly and strongly tuberculate, tomentose, tips closely appressed; nut light brown, ovoid or oblong, 8-12 mm, nearly glabrous. |
biennial; cup shallowly saucer-shaped, 3-6.5 mm high × 7.5-11 mm wide, covering 1/4-1/3 nut, outer surface puberulent, inner surface light brown, pubescent, scale tips tightly appressed, acute; nut ovoid to hemispheric, 8-12 × 6.5-10 mm, often striate, glabrate, scar diam. 4.5-6 mm. |
Cotyledons | connate. |
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Terminal | buds chestnut brown, ovoid, 2-4 mm, apex acute, glabrous. |
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Quercus arizonica |
Quercus phellos |
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Phenology | Flowering spring. | Flowering spring. |
Habitat | Oak and pinyon woodlands, margins of chaparral, arroyos | Of bottomland flood plains, also on stream banks, dunes, and terraces, and, occasionally, on poorly drained uplands |
Elevation | 1300-2500(-3000) m (4300-8200(-9800) ft) | 0-400 m (0-1300 ft) |
Distribution |
AZ; NM; TX; Mexico (Chihuahua, Coahuila, Durango, and Sonora)
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AL; AR; DC; DE; FL; GA; IL; KY; LA; MD; MO; MS; NC; NJ; NY; OK; PA; SC; TN; TX; VA
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Discussion | Some of the specimens previously referred to Quercus endemica by C. H. Muller belong here instead. Putative hybrids between Quercus arizonica and Q. grisea (= Q. ×organensis Trelease) are problematic in local areas of contact from southeastern Arizona to western Texas. These intermediates tend to have narrower leaves than Q. arizonica, with moderately reticulate patterns of venation, and more densely hairy leaves. Quercus arizonica and Q. grisea are amply distinct elsewhere, including large areas in northern Mexico, and they appear to be more closely related to other species than to one another (e.g., Q. arizonica with Q. oblongifolia and Q. laeta Liebmann, and Q. grisea with Q. mohriana and Q. microphylla Née). Thus, Q. arizonica and Q. grisea are best treated as distinct species that hybridize, and not as conspecific populations. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Individual trees with leaves softly pubescent abaxially may be classified as Quercus phellos forma intonsa Fernald; however, such leaves are known to occur on second-flush shoots from twigs bearing typical leaves. Quercus phellos reportedly hybridizes with Q. coccinea (W. W. Ashe 1894); with Q. ilicifolia (= Q. ×giffordi Trelease) and Q. incana (E. J. Palmer 1948); and with Q. marilandica, Q. nigra, Q. pagoda (= Q. ×ludoviciana Sargent), Q. palustris, Q. rubra, Q. shumardii, and Q. velutina. D. M. Hunt (1989) cited evidence of hybridization also with Q. hemisphaerica, Q. imbricaria, Q. laurifolia, and Q. pumila. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 3. | FNA vol. 3. |
Parent taxa | Fagaceae > Quercus > sect. Quercus | Fagaceae > Quercus > sect. Lobatae |
Sibling taxa | ||
Synonyms | Q. sacame | |
Name authority | Sargent: Gard. & Forest 8: 92. (1895) | Linnaeus: Sp. Pl. 2: 994. (1753) |
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