Quercus engelmannii |
Quercus vaseyana |
|
---|---|---|
Engelmann oak, Engelmann's oak |
sandpaper oak, Vasey oak |
|
Habit | Trees, subevergreen, to 10 m. Bark gray or whitish, closely furrowed. | Shrubs or small trees, evergreen or subevergreen, to 10 m. Bark dark brown, furrowed and exfoliating in long strips. |
Twigs | light brown, 1-1.5 mm diam., densely or sparsely stellate-tomentose, soon glabrate. |
reddish or grayish brown, 1-1.5 mm diam., short stellate-tomentose or tomentulose, later glabrate or persistently pubescent, rarely glabrous. |
Buds | reddish brown, subspheric to broadly ovoid, 1-2 mm, glabrous or basal scales pubescent; stipules persistent about terminal buds. |
dark red-brown or gray, round-ovoid, 1-1.5 mm, apex obtuse, sparsely pubescent or glabrate. |
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 narrowly lanceolate to usually oblong, mostly planar or slightly convex, 20-60(-90) × 10-20 mm, often rather leathery, base cuneate to rounded, margins coarsely 3-5-toothed on each side or shallowly lobed or entire, with teeth or lobes acute or obtuse, mucronate-tipped, secondary veins 4-6 on each side, usually branched, apex acute, rarely obtuse; surfaces abaxially densely stellate with minute appressed hairs, rarely glabrate and lustrous green, adaxially dark green, lustrous, glabrous or very sparsely stellate-puberulent. |
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 peduncle 2-3 mm; cup saucer-shaped to cup-shaped, 3-4 mm deep × 10 mm wide, margin thin, scales reddish brown, strongly, regularly tuberculate; nut light brown, ovoid to oblong or subcylindric, to 12 × 12 mm, glabrous. |
Cotyledons | connate. |
distinct. |
2n | = 24. |
|
Quercus engelmannii |
Quercus vaseyana |
|
Phenology | Flowering in spring. | Flowering spring. |
Habitat | Oak woodlands, margins of chaparral, arroyos, slopes and bajadas | Dry limestone slopes, oak and mesquite woodlands, juniper woodlands, and canyons and ravines in otherwise dry, open grasslands, sometimes descending into margins of dry scrub |
Elevation | 50-1200 m (200-3900 ft) | 300-600 m (1000-2000 ft) |
Distribution |
CA; Mexico (Baja California)
|
TX; Mexico (Chihuahua, Coahuila, and Nuevo León) |
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.) |
Apparent hybridization between Quercus vaseyana and Q. pungens is discussed under the latter species. (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. pungens var. vaseyana, Q. undulata var. vaseyana | |
Name authority | Greene: Ill. W. Amer. Oaks 1: 33, plate 17. (1889) | Buckley: Bull. Torrey Bot. Club 10: 91. (1883) |
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