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.
Tree 15 - 22 m tall, trunk 30 cm - 0.75 m in diameter Leaves: alternate, odd-pinnately compound, 15 - 30 cm long, with five to seven leaflets. Flowers: either male or female, found on the same tree (monoecious), male flowers in clusters of three hanging catkins 8 - 18 cm long, female flowers in short spikes of two to five. Fruit: a nut surrounded by a husk, 2 - 4.5 cm long, 2 - 3.5 cm wide. The husk is tan to reddish brown, pear-shaped to elliptical or spherical, sometimes splitting to the base, and the nut is sometimes four-ribbed. Bark: light gray, developing thin fissures with interlacing ridges. Twigs: shiny, changing from green to reddish to gray. Terminal buds: green to gray, 0.5 - 1.5 cm long, dome-shaped, hairy, with the outer scales dropping in autumn. Leaflets: shiny yellowish green above, paler beneath, 7 - 16 cm long, 2 - 5 cm wide, the terminal leaflet largest, oblong to egg- or lance-shaped, toothed, hairy-veined beneath. Leaves turn golden in fall. Foliage is aromatic when crushed.
Similar species: Carya cordiformis can be distinguished from other hickories by its sulfur-yellow buds that appear naked, nine narrow leaflets, fruit with a husk that splits to the middle, and bark that remains tight. Carya laciniosa has shaggy bark, stout orangish tan twigs with orange lenticels, seven leaflets with soft hairs beneath, very large oblong to spherical and four- to six-ridged nuts with husks splitting to the base, and large terminal buds with slightly curling outer scales. Carya ovata differs by its shaggy bark, foliage that smells like apples when crushed, five leaflets fringed with tufts of hair along the margins, nearly spherical husks that separate from a four-ridged nut, and large terminal buds with slightly curling outer scales. Carya tomentosa has fissured bark, densely hairy and reddish brown twigs, seven to nine leaflets with hairs beneath, and husks that split to the middle or base to reveal four-ridged nuts.
Flowering: May to June
Habitat and ecology: Occasionally found in dry upland woods.
Occurence in the Chicago region: native
Notes: The wood of C. glabra is used to make sporting equipment, tool handles, and furniture.
Etymology: Carya comes from the Greek name for walnut. Glabra means "without hairs."
Bark light or dark gray, on younger trunks tight and patterned, becoming finely furrowed and checked, later rough and deeply furrowed; outer bud-scales sparsely resinous-dotted, otherwise glabrous; petiole, rachis, and lower lf-surface soon glabrous, or pubescent only on the larger veins and in the vein-axils; lfls usually 5(7), the terminal one broadly oblanceolate to obovate; fr subglobose to obovoid, 2-3.5(-5) cm; husk 2-6 mm thick, eventually dehiscent to the middle, sometimes only along one or two sutures; nut 2-3 cm, rather thin-shelled, pale buff, slightly 4-angled or smooth, round or compressed; kernel astringent, scarcely edible, varying to bland; 2n=64. Upland woods; s. Vt. and se. N.H. to Mich., se. Io., and e. Kans., s. to Fla. and e. Tex.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.