Trees, rarely shrubs , deciduous, with gray or brownish bark. Terminal buds larger than lateral buds. Leaves alternate [or opposite], aromatic, usually odd-, rarely even-, pinnately compound; stipules absent; petiole present. Leaflets 3-23, margins serrate or entire. Inflorescences: staminate catkins solitary or fasciculate, pendulous, elongate, on reduced shoots arising on branches of previous year or at base of current year's growth; pistillate catkins solitary or few-flowered spikes [or many-flowered racemes]. Flowers unisexual, staminate and pistillate on same plants; bract 1, bracteoles (0-)2. Staminate flowers: calyx 2-6-lobed or absent; corolla absent; stamens 3-50; filaments very short or absent; anthers usually pubescent. Pistillate flowers: calyx 4-lobed or absent; corolla absent; ovary 1, inferior, usually 2-carpellate, 1-locular distally; ovule 1; stigmas 2, fleshy or plumose. Fruits large nuts [or samaras], nuts enclosed in dehiscent or indehiscent, fibrous-fleshy or hard involucres (husks), thus ± drupelike. Seeds 1; endosperm absent; cotyledons fleshy and oily, variously lobed.
Trees or rarely shrubs, deciduous, semievergreen, or evergreen, monoecious or rarely dioecious; bark tight (or exfoliating). Branchlets with solid or chambered pith. Terminal buds subglobose or ovoid to oblong, naked or with scales. Stipules absent. Leaves alternate (or opposite), odd- or even-pinnate, sometimes trifoliolate, rarely simple; leaflets with glandular, peltate scales, often resinous and aromatic, particularly conspicuous abaxially on young leaves and twigs, margin serrate or rarely entire. Inflorescences pendulous or sometimes erect, lateral or terminal, on reduced shoots arising on branchlets of previous year (old growth) or on current year’s growth (new growth), of several types: androgynous panicle with male, lateral spikes and female, central spike; androgynous panicle with male, mainly lateral spikes and female, central spike male at apex; cluster of male spikes and solitary female spike; or solitary male and female spikes. Flowers unisexual, anemophilous, rarely entomophilous. Male flowers subtended by an entire or 3-lobed bract; bracteoles 2 or absent; sepals 0-4, adnate to receptacle when present; stamens 3-40(-100), inserted on receptacle; filaments short to nearly absent, free or united at base; anthers glabrous or pubescent, 2-loculed, dehiscing longitudinally. Female flowers with an entire or 3-lobed bracts; bracteoles 2 or 3 (or absent); sepals 0-4, adnate to ovary, free at apex; gynoecium of 2 carpels united into an inferior ovary, 1-loculed, but at base 2-4(-8)-loculed; style 1, short or elongate, rarely absent; stigmas 2, carinal or commissural, sometimes 4-lobed, plumose or fleshy; ovule 1, orthotropous. Fruiting spike elongate, and pendulous or short and erect, rarely conelike. Fruit a drupelike nut, 2-4(-8)-chambered at base, with a dehiscent or indehiscent husk, or a 2- or 3-winged or disc-winged nutlet. Seed solitary, without endosperm. Cotyledons 4-lobed, much contorted. Germination hypogeal or epigeal. 2n = (28), 32, (64).
Elias, T. S. 1972. The genera of Juglandaceae in the southeastern United States. J. Arnold Arbor. 53: 26-51. Manchester, S. R. 1987. The fossil history of the Juglandaceae. Monogr. Syst. Bot. Missouri Bot. Gard. 21: 1-137. Manning, W. E. 1978. The classification within the Juglandaceae. Ann. Missouri Bot. Gard. 65: 1058-1087. Stone, D. E. 1993. Juglandaceae. In: K. Kubitzki et al., eds. 1990+. The Families and Genera of Vascular Plants. 2 +vols. Berlin etc. Vol. 2, pp. 348-359.