Northern pin oak, jack oak, Hill's oak

Quercus ellipsoidalis var. kaposianensis J. W. Moore

Trees , deciduous, to 20 m; lower trunk often with stubs of dead branches. Bark dark gray-brown, shallowly fissured, inner bark orangish. Twigs dark reddish brown, (1-)1.5-3 mm diam., glabrous. Terminal buds dark reddish brown, ovoid, 3-5 mm, often conspicuously 5-angled in cross section, usually silvery- or tawny-pubescent toward apex. Leaves: petiole 20-50 mm, glabrous. Leaf 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. 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.

Flowering spring. Dry sandy sites, rarely on moderately mesic slopes or uplands; 150-500 m; Ont.; Ill., Ind., Iowa, Mich., Minn., Ohio, Wis.

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).