Flora of North America species comparison

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Quercus nigra

Quercus ajoensis

chêne gris, water oak

Ajo Mountain scrub oak
Habit Trees, deciduous or tardily deciduous, to 30 m. Bark grayish black, fissures irregular, shallow, inner bark pinkish. Shrubs, rarely trees, evergreen, to 2-3 m. Bark gray, scaly or furrowed.
Twigs

dark red-brown, 1.5-2.5 mm diam., glabrous.

light brown, 1-2 mm diam., inconspicuously short stellate-pubescent or glabrate.
Buds

brown or reddish brown, ovoid or globose, 1-1.5 mm, variously short stellate-pubescent, tomentose, or glabrate.
Leaves

blade distinctly obtrullate, rarely elliptic or merely obovate, widest near apex, 30-120(-160) × 15-60(-70) mm, base attenuate or cuneate, rarely rounded, margins entire with 1 apical awn or with 2-3 shallow lobes and 2-5 awns (leaves on juvenile or 2d-flush growth may be deeply lobed with more awns), apex obtuse to blunt or rounded;

surfaces abaxially glabrous except for minute or conspicuous axillary tufts of tomentum, veins rarely raised, adaxially glabrous with secondary veins somewhat impressed.

petiole (2-)3-4 m. Leaf blade ovate to narrowly ovate or oblong, (10-)15-35(-50) × (5-)10-20(-30) mm, rather leathery, base cordate, rarely rounded, margins crispate, sometimes flat, cartilaginous, with 4-6(-8) long-attenuate, spinose-awned teeth on each side, secondary veins 5-8 on each side, whitish, apex acute or obtuse with bristly distal teeth;

surfaces abaxially blue-green, waxy-glaucous, microscopically papillose, glabrous, sometimes sparsely stellate-pubescent along midrib, adaxially blue-green, glaucous, glabrous or sparingly stellate-pubescent along midrib, secondary veins raised on both surfaces.
Acorns

biennial;

cup saucer-shaped, 2.5-5.5 mm high × 10-18 mm wide, covering 1/4 nut or less, outer surface puberulent, inner surface sparsely to uniformly pubescent, scale tips tightly appressed, acute;

nut broadly ovoid, 9.5-14 × 9.5-14.5 mm, often faintly striate, glabrate, scar diam. 6-11.5 mm.

solitary or paired on thin axillary peduncle (5-)30-50 mm;

cup shallowly cup-shaped, thin, 3-4 mm deep × 6-8(-10) mm wide, enclosing only base of nut, scales brownish, moderately tuberculate, pubescent;

nut oblong to narrowly ovoid, 12-15 × 5-8 mm.
Cotyledons

distinct.
Terminal

buds reddish brown, ovoid, 3-6.5 mm, puberulent throughout, occasionally densely pubescent on apical 2/3.

Quercus nigra

Quercus ajoensis
Phenology Flowering spring. Flowering in spring.
Habitat Mesic alluvial and lowland sites, also barrens, dunes, hammocks, and low ridges to steep slopes Rare to locally abundant on igneous slopes
Elevation 0-450 m (0-1500 ft) 500-1500 m (1600-4900 ft)
Distribution
from FNA
AL; AR; DE; FL; GA; KY; LA; MD; MO; MS; NC; NJ; OK; SC; TN; TX; VA
[WildflowerSearch map]
[BONAP county map]
from FNA
AZ; Mexico (Baja California)
[BONAP county map]
Discussion

Typically on mesic alluvial and lowland sites, Quercus nigra also occurs on a wide variety of soil types and in a diversity of habitats.

Trees with 3-lobed leaves with attenuate bases have been recognized as Quercus nigra var. tridentifera Sargent.

Quercus nigra reportedly hybridizes with Q. falcata (= Q. ×garlandensis E. J. Palmer), Q. incana, Q. laevis (= Q. ×walteriana Ashe), Q. marilandica (= Q. ×sterilis Trelease), Q. phellos (= Q. ×capesii W. Wolf), Q. shumardii (= Q. ×neopalmeri Sudworth), and Q. velutina (Q. ×demarei Ashe). In addition, D. M. Hunt (1989) cited evidence of hybridization also with Q. arkansana, Q. georgiana, Q. hemisphaerica, Q. laurifolia, Q. myrtifolia, Q. palustris, Q. rubra, and Q. texana.

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

Populations of Quercus ajoensis in southern New Mexico show characteristics suggesting introgression from hybridization with Quercus toumeyi, such as increased twig and leaf pubescence and sometimes the prominent golden puberulum of the abaxial leaf surfaces. Hybrids between Q. ajoensis and both Q. turbinella and Q. gambelii (Utah) are also known.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 3. FNA vol. 3.
Parent taxa Fagaceae > Quercus > sect. Lobatae Fagaceae > Quercus > sect. Quercus
Sibling taxa
Q. acerifolia, Q. agrifolia, Q. ajoensis, Q. alba, Q. arizonica, Q. arkansana, Q. austrina, Q. berberidifolia, Q. bicolor, Q. boyntonii, Q. buckleyi, Q. carmenensis, Q. chapmanii, Q. chihuahuensis, Q. chrysolepis, Q. coccinea, Q. cornelius-mulleri, Q. depressipes, Q. douglasii, Q. dumosa, Q. durata, Q. ellipsoidalis, Q. emoryi, Q. engelmannii, Q. falcata, Q. fusiformis, Q. gambelii, Q. garryana, Q. geminata, Q. georgiana, Q. graciliformis, Q. gravesii, Q. grisea, Q. havardii, Q. hemisphaerica, Q. hinckleyi, Q. hypoleucoides, Q. ilicifolia, Q. imbricaria, Q. incana, Q. inopina, Q. intricata, Q. john-tuckeri, Q. kelloggii, Q. laceyi, Q. laevis, Q. laurifolia, Q. lobata, Q. lyrata, Q. macrocarpa, Q. margarettae, Q. marilandica, Q. michauxii, Q. minima, Q. mohriana, Q. montana, Q. muehlenbergii, Q. myrtifolia, Q. oblongifolia, Q. oglethorpensis, Q. pacifica, Q. pagoda, Q. palmeri, Q. palustris, Q. phellos, Q. polymorpha, Q. prinoides, Q. pumila, Q. pungens, Q. robur, Q. robusta, Q. rubra, Q. rugosa, Q. sadleriana, Q. shumardii, Q. similis, Q. sinuata, Q. stellata, Q. tardifolia, Q. texana, Q. tomentella, Q. toumeyi, Q. turbinella, Q. vacciniifolia, Q. vaseyana, Q. velutina, Q. viminea, Q. virginiana, Q. wislizenii
Q. acerifolia, Q. agrifolia, Q. alba, Q. arizonica, Q. arkansana, Q. austrina, Q. berberidifolia, Q. bicolor, Q. boyntonii, Q. buckleyi, Q. carmenensis, Q. chapmanii, Q. chihuahuensis, Q. chrysolepis, Q. coccinea, Q. cornelius-mulleri, Q. depressipes, Q. douglasii, Q. dumosa, Q. durata, Q. ellipsoidalis, Q. emoryi, Q. engelmannii, Q. falcata, Q. fusiformis, Q. gambelii, Q. garryana, Q. geminata, Q. georgiana, Q. graciliformis, Q. gravesii, Q. grisea, Q. havardii, Q. hemisphaerica, Q. hinckleyi, Q. hypoleucoides, Q. ilicifolia, Q. imbricaria, Q. incana, Q. inopina, Q. intricata, Q. john-tuckeri, Q. kelloggii, Q. laceyi, Q. laevis, Q. laurifolia, Q. lobata, Q. lyrata, Q. macrocarpa, Q. margarettae, Q. marilandica, Q. michauxii, Q. minima, Q. mohriana, Q. montana, Q. muehlenbergii, Q. myrtifolia, Q. nigra, Q. oblongifolia, Q. oglethorpensis, Q. pacifica, Q. pagoda, Q. palmeri, Q. palustris, Q. phellos, Q. polymorpha, Q. prinoides, Q. pumila, Q. pungens, Q. robur, Q. robusta, Q. rubra, Q. rugosa, Q. sadleriana, Q. shumardii, Q. similis, Q. sinuata, Q. stellata, Q. tardifolia, Q. texana, Q. tomentella, Q. toumeyi, Q. turbinella, Q. vacciniifolia, Q. vaseyana, Q. velutina, Q. viminea, Q. virginiana, Q. wislizenii
Synonyms Q. nana, Q. nigra var. tridentifera, Q. uliginosa Q. turbinella subsp. ajoensis, Q. turbinella var. ajoensis
Name authority Linnaeus: Sp. Pl. 2: 995. (1753) C. H. Muller: Madroño 12: 140. (1954)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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