1. Juglans regia Linnaeus, Sp. Pl. 2: 997. 1753.
胡桃 hu tao
Juglans duclouxiana Dode; J. fallax Dode; J. kamaonia (C. de Candolle) Dode; J. orientis Dode; J. regia var. sinensis C. de Candolle; J. sinensis (C. de Candolle) Dode.
Trees to 25 m tall. Leaves 25-30 cm; petiole 5-7 cm; petiole and rachis glabrescent, without glandular hairs; leaflets (3 or)5-9, entire on mature trees, sometimes obscurely serrulate on young plants; lateral leaflets subsessile or petiolule 1-2 mm, blade elliptic-ovate to long elliptic, 6-15 × 3-6 cm, abaxially glabrous except for tufts of hairs in vein axils, without glandular hairs, base oblique, subrounded, apex obtuse or acute to shortly acuminate; terminal petiolule 2.5-6 cm. Male spike 5-10(-15) cm. Stamens 6-30(-40). Fruiting spike usually with 1-3(-38) nuts. Nuts subglobose, 4-6 cm; husk glabrous, irregularly dehiscent; shell thick except in commercial varieties, wrinkled. Fl. Apr-May, fr. Oct. 2n = 32.
Mountain slopes; 500-1800(-4000) m. Widely distributed in C, E, NW, and SW China [SW Asia to Himalayas, SE Europe]
Commonly cultivated in China from 23-42° N for its edible, oily nuts and hard, fine grained wood. Juglans regia has a very long history of cultivation in China and elsewhere; as a result, there are many cultivars, including five Chinese taxa that L.-A. Dode (Bull. Soc. Dendrol. France 2: 67-98. 1906), recognized on the basis of differences in shell thickness, size, etc.