Quercus engelmannii |
Quercus durata |
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Engelmann oak, Engelmann's oak |
leather oak |
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Habit | Trees, subevergreen, to 10 m. Bark gray or whitish, closely furrowed. | Shrubs, evergreen, 1-2(-3) m. Bark scaly. | ||||
Twigs | light brown, 1-1.5 mm diam., densely or sparsely stellate-tomentose, soon glabrate. |
gray or yellowish, 1-3 mm diam., densely or sparsely tomentulose, often with prominent, yellowish, spreading hairs. |
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Buds | reddish brown, subspheric to broadly ovoid, 1-2 mm, glabrous or basal scales pubescent; stipules persistent about terminal buds. |
brown or reddish brown, ovoid or globose, 1-2 mm, glabrous or puberulent. |
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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 cupped or convex, rarely somewhat planar, (10-)15-40 × 7-15(-20) mm, base cuneate, rounded-attenuate, or truncate, margins entire or irregularly toothed, sometimes spinose, usually unevenly revolute, secondary veins 4-6 on each side, apex rounded or subacute; surfaces abaxially densely to sparsely covered with erect, stipitate, (1-)2-4(-6)-rayed hairs 1-4 mm, felty to touch, secondary veins prominent, adaxially grayish or yellowish, with dense or scattered, semi-erect or appressed hairs, secondary veins obscure or somewhat impressed. |
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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. |
solitary or paired, subsessile; cup reddish, hemispheric, deeply cup-shaped or turbinate, 4-6 mm deep × 12-18 mm wide, enclosing to 1/2 nut or more, scales reddish or yellowish, weakly to strongly tuberculate, often somewhat glandular; nut globose, ovoid or cylindric, 15-25 × 10-25 mm, apex rounded or obtuse, persistently minute-puberulent. |
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Cotyledons | connate. |
distinct. |
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2n | = 24. |
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Quercus engelmannii |
Quercus durata |
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Phenology | Flowering in spring. | |||||
Habitat | Oak woodlands, margins of chaparral, arroyos, slopes and bajadas | |||||
Elevation | 50-1200 m (200-3900 ft) | |||||
Distribution |
CA; Mexico (Baja California)
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CA
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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.) |
Chaparral, oak woodlands, open pine forests, on serpentine and nonserpentine soils; 150-1500 m. Varieties 2 (2 in the flora). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 3. | FNA vol. 3. | ||||
Parent taxa | Fagaceae > Quercus > sect. Quercus | Fagaceae > Quercus > sect. Quercus | ||||
Sibling taxa | ||||||
Subordinate taxa | ||||||
Synonyms | Q. dumosa var. bullata, Q. dumosa var. revoluta | |||||
Name authority | Greene: Ill. W. Amer. Oaks 1: 33, plate 17. (1889) | Jepson: Fl. Calif. 1(2): 356. (1909) | ||||
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