Quercus engelmannii |
Quercus austrina |
|
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Engelmann oak, Engelmann's oak |
bastard white oak, bluff oak |
|
Habit | Trees, subevergreen, to 10 m. Bark gray or whitish, closely furrowed. | Trees, deciduous, to 20(-25) m. Bark pale gray, scaly, eventually divided into broad ridges. |
Twigs | light brown, 1-1.5 mm diam., densely or sparsely stellate-tomentose, soon glabrate. |
dark brown to somewhat reddish, 2-2.5 mm diam., often with prominent, corky, white lenticels. |
Buds | reddish brown, subspheric to broadly ovoid, 1-2 mm, glabrous or basal scales pubescent; stipules persistent about terminal buds. |
dark reddish brown, ovoid, distally acute, 3-5 × 2-2.5 mm, puberulent. |
Leaves | blade oblong to elliptic, occasionally lanceolate or ovate, (20-)30-60(-80) × (5-)10-20(-25) mm, base cuneate to cordate, margins entire, undulate, sometimes irregularly toothed, especially toward apex, secondary veins 7-8(-10) on each side, branched, apex acute or broadly rounded; surfaces abaxially blue-green or pale green, densely and loosely glandular-tomentose, quickly glabrate or persistently floccose, especially about base of midrib, at maturity strongly glaucous, adaxially gray-green or pale green, bluish green or glaucous. |
blade green or grayish green, narrowly obovate or elliptic, (40-)70-100(-200) × (13-)30-50(-115) mm, base cuneate or attenuate, margins sinuately and irregularly shallowly lobed, lobes rounded, sometimes obtuse, secondary veins 4-6(-8) on each side, apex narrowly or broadly rounded; surfaces abaxially loosely covered with semi-erect stellate hairs to 0.5 mm diam., glabrous at maturity, often with a few hairs remaining along veins near midrib, adaxially glabrous, glossy. |
Acorns | solitary or paired, subsessile or on peduncle to 5-6 mm; cup cup-shaped or shallowly cup-shaped, 8-10 mm deep × 10-15 mm wide, enclosing 1/3 nut, scales 1.5-3 mm wide, strongly and regularly tuberculate near base of cup, gray-pubescent; nut light brown, ovoid or oblong, 15-25 × 12-14 mm, glabrate or puberulent about apex. |
subsessile or on stout axillary peduncle to 15 mm; cup hemispheric or deeply goblet- or cup-shaped, 9-10 mm deep × 10-13 mm wide, enclosing 1/3-1/2 nut, scales loosely appressed, gray, narrowly ovate, sometimes thickened near base, not tuberculate, canescent; nut ovoid or elliptic, 17 × 12 mm. |
Cotyledons | connate. |
distinct. |
2n | = 24. |
|
Quercus engelmannii |
Quercus austrina |
|
Phenology | Flowering in spring. | Flowering spring. |
Habitat | Oak woodlands, margins of chaparral, arroyos, slopes and bajadas | River bottoms, wet forests, flatwoods |
Elevation | 50-1200 m (200-3900 ft) | 0-200 m (0-700 ft) |
Distribution |
CA; Mexico (Baja California)
|
AL; FL; GA; MS; NC; SC
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Discussion | Quercus engelmannii is closely related to and possibly conspecific with Q. oblongifolia. The cups of Q. engelmannii are larger, deeper, and generally more tuberculate than those of Q. oblongifolia, and the scales are usually larger. Based on available samples, the nuts of Q. engelmannii are consistently larger than those of Q. oblongifolia, apparently with little, if any, overlap in diameter. Considerably more variation occurs within Q. engelmannii in leaf form, possibly reflecting introgression from other white oak species such as Q. cornelius-mulleri, Q. dumosa, and Q. durata (see treatment). On Catalina Island, Quercus engelmannii is known only from a small grove of trees. Putative hybrids between Q. engelmannii and Q. cornelius-mulleri are common in areas of contact between the two species in Riverside and San Diego counties in southern California. Such a population was the basis for Q. acutidens Torrey [Q. dumosa var. acutidens (Torrey) Wenzig]. Other names applied to those populations are Q. macdonaldii var. elegantula Greene and Q. dumosa var. elegantula (Greene) Jepson. Variable in leaf form and stature, those intermediates form extensive populations and are probably best disposed of under the name Q. ×acutidens. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Quercus austrina is probably the most misunderstood oak of the southeastern United States. Although the species is fairly widespread, it is apparently abundant only in local areas and is poorly represented in herbaria. This may be partly because Q. austrina is often misidentified as Q. sinuata, which it superficially resembles, or as Q. nigra, a red oak with similarly shaped leaves. It is easily distinguished from Q. sinuata by its larger, more acute buds; darker twigs; deeper, turbinate acorn cups; and absence of minute, appressed, stellate hairs on the abaxial leaf surface. Instead, Q. austrina has a tomentum of soft erect hairs on young leaves, and glabrate mature leaves. (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. Quercus |
Sibling taxa | ||
Synonyms | Q. durandii var. austrina | |
Name authority | Greene: Ill. W. Amer. Oaks 1: 33, plate 17. (1889) | Small: Fl. S.E. U.S., 353. (1903) |
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