11. Carya glabra (Miller) Sweet, Hort. Brit. 97. 1826.
Pignut hickory, sweet pignut
Juglans glabra Miller, Gard. Dict. ed. 8., Juglans no. 5. 1768; Carya glabra var. megacarpa Sargent; C. glabra var. odorata (Marshall) Little; C. leiodermis Sargent; C. magnifloridana Murrill; C. ovalis (Wangenheim) Sargent; C. ovalis var. hirsuta (Ashe) Sargent; C. ovalis var. obcordata (Muhlenberg & Willdenow) Sargent; C. ovalis var. obovalis Sargent; C. ovalis var. odorata (Marshall) Sargent; Hicoria austrina Small; H. microcarpa (Nuttall) Britton
Trees , to 30 m. Bark light gray, smooth or fissured or exfoliating with small platelike scales or narrow strips. Twigs reddish brown, slender, essentially glabrous or sparsely scaly. Terminal buds reddish brown to tan, ovoid, 5-15 mm; outer scales sparsely scaly, hirsute to glabrous, inner scales finely pubescent, sparsely scaly, bud scales imbricate; axillary buds protected by bracteoles fused into hood. Leaves 2-6 dm; petiole 3-14 cm, glabrous to moderately pubescent near rachis, moderately scaly, rachis glabrous or finely puberulent. Leaflets (3-)5-7(-9), lateral petiolules 0-2 mm, terminal petiolules 2-18 mm; blades ovate to elliptic or obovate, not falcate 4-21 × 2-10 cm, margins finely to coarsely serrate, apex acuminate to narrowly acuminate; surfaces abaxially glabrous to densely pubescent with unicellular and 2-4-rayed fasciculate hairs, large peltate scales and small irregular, round, and 4-lobed peltate scales in spring, usually becoming glabrous in fall, adaxially scaly in spring. Staminate catkins pedunculate, to 13 cm, stalks glabrous or densely pubescent, bracts hirsute at tips; anthers hirsute. Fruits tan to reddish brown, obovoid, spheric or ellipsoid, not compressed to compressed, not angled, 2-4.5 × 2-3.5 cm; husks rough, 2-5 mm thick, partially dehiscent or dehiscing to base, sutures smooth or slightly winged; nuts tan, obovoid to ellipsoid, not compressed to compressed, not angled, rugulose; shells thick. Seeds sweet.
Flowering spring. Edge of bayous, deep flood plains, well-drained sandy soils, rolling hills and slopes, dry rocky soils, or thin soils on edge of granite outcrops; 0-800 m; Ont.; Ala., Ark., Conn., Del., D.C., Fla., Ga., Ill., Ind., Iowa, Kans., Ky., La., Md., Mass., Mich., Miss., Mo., N.H., N.J., N.Y., N.C., Ohio, Okla., Pa., R.I., S.C., Tenn., Tex., Vt., Va., W.Va.
Carya glabra is a highly polymorphic species. Tight-barked trees bearing large pear-shaped fruits are common along the Gulf Coast ( C . glabra var. megacarpa and C . leiodermis , C . magnifloridana ). Trees with exfoliating bark, reddish petioles, and small, compressed, ellipsoid fruits that dehisce to the base (i.e., C . ovalis ) are more common at higher latitudes. Carya glabra intergrades with C . floridana , C . pallida , and C . texana , and it is reported to hybridize with the diploid C . cordiformis ( C . × demareei Palmer). The extreme northern ovalis form of the species also appears to hybridize with the typical glabra in areas of sympatry.