Quercus ellipsoidalis |
Quercus engelmannii |
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Hill's oak, Jack oak, northern pin oak |
Engelmann oak, Engelmann's oak |
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Habit | Trees, deciduous, to 20 m; lower trunk often with stubs of dead branches. | Trees, subevergreen, to 10 m. Bark gray or whitish, closely furrowed. |
Bark | dark gray-brown, shallowly fissured, inner bark orangish. |
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Twigs | dark reddish brown, (1-)1.5-3 mm diam., glabrous. |
light brown, 1-1.5 mm diam., densely or sparsely stellate-tomentose, soon glabrate. |
Buds | reddish brown, subspheric to broadly ovoid, 1-2 mm, glabrous or basal scales pubescent; stipules persistent about terminal buds. |
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Leaves | blade elliptic, 70-130 × 50-100 mm, base obtuse to truncate, margins with 5-7 deep lobes and 15-55 awns, lobes distally expanded, sinuses usually extending more than 1/2 distance to midrib, apex acute; surfaces abaxially glabrous except for minute axillary tufts of tomentum, adaxially glossy light green, glabrous, secondary veins raised on both surfaces. |
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. |
Acorns | biennial; cup narrowly turbinate to deeply cup-shaped, 6-11 mm high × 10-19 mm wide, covering 1/3-1/2 nut, outer surface reddish brown, puberulent, inner surface light brown, glabrous, rarely with ring of pubescence around scar, scales with straight or slightly concave margins, tips tightly appressed, obtuse or acute; nut ellipsoid to ovoid, rarely subglobose, 10-20 × 9-15 mm, occasionally striate, glabrous, occasionally with 1 or more faint rings of fine pits at apex, scar diam. 4-8 mm. |
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. |
Cotyledons | connate. |
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Terminal | buds dark reddish brown, ovoid, 3-5 mm, often conspicuously 5-angled in cross section, usually silvery- or tawny-pubescent toward apex. |
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2n | = 24. |
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Quercus ellipsoidalis |
Quercus engelmannii |
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Phenology | Flowering spring. | Flowering in spring. |
Habitat | Dry sandy sites, rarely on moderately mesic slopes or uplands | Oak woodlands, margins of chaparral, arroyos, slopes and bajadas |
Elevation | 150-500 m (500-1600 ft) | 50-1200 m (200-3900 ft) |
Distribution |
IA; IL; IN; MI; MN; OH; WI; ON
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CA; Mexico (Baja California)
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Discussion | In many treatments (e.g., E. G. Voss 1972+, vol. 2), Quercus ellipsoidalis is included in Q. coccinea. Variation in fruit morphology has led to recognition of several formae (W. Trelease 1919; see also R. J. Jensen 1986) and one variety (Q. ellipsoidalis var. kaposianensis, based on specimens from St. Paul, Minnesota, in which the cup tightly encloses the nut for two-thirds its length at maturity). Quercus ellipsoidalis reportedly hybridizes with Q. rubra and Q. velutina. The Menominee used Quercus ellipsoidalis medicinally to treat suppressed menses caused by cold (D. E. Moerman 1986). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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.) |
Source | FNA vol. 3. | FNA vol. 3. |
Parent taxa | Fagaceae > Quercus > sect. Lobatae | Fagaceae > Quercus > sect. Quercus |
Sibling taxa | ||
Synonyms | Q. ellipsoidalis var. kaposianensis | |
Name authority | E. J. Hill: Bot. Gaz. 27: 204, plates 2, 3. (1899) | Greene: Ill. W. Amer. Oaks 1: 33, plate 17. (1889) |
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