Castanea
Gard. Dict. Abr. ed. 4. 1754.
Trees or shrubs, winter-deciduous, sometimes rhizomatous. Terminal buds absent, pseudoterminal bud (axillary bud of youngest leaf) ovoid, with 2 unequal opposite outer scales enclosing several imbricate inner scales. Leaves: stipules prominent on new growth, soon deciduous. Leaf blade thin, somewhat leathery, secondary veins unbranched, ±parallel, extending to margin, each vein ending in sharp tooth or well-developed awn. Inflorescences staminate or androgynous, axillary, spicate, erect, rigid or flexible; androgynous inflorescences with pistillate cupules/flowers toward base and staminate flowers distally. Staminate flowers: sepals distinct; stamens 12(-18), typically surrounding indurate pistillode covered with silky hairs. Pistillate flowers 1-3 per cupule; sepals distinct; carpels and styles typically 6(-9). Fruits: maturation in 1st year following pollination (termed annual by many authors); cupule 2-4-valved, valves connate marginally until maturity, ±completely enclosing nut(s), spiny, spines irregularly branched, often interlocking, densely or sparsely covered in simple hairs; nuts 1-3 per cupule, plano-convex, or if 3, then central nut often reduced and flattened, or if solitary, then often rounded in cross section, not winged, adjacent nuts not separated by internal cupule valves. x = 12.
Distribution
North America, Europe, Asia.
Discussion
Species ca. 8-10 (3 in the flora, often interpreted as 2).
As evidenced by United States breeding programs, all species are probably interfertile (including American × Asian species). Local morphologic intergradation between species is to be expected.
Selected References
Lower Taxa
Key
| 1 | Cupules 4-valved, enclosing 3 flowers/fruits; leaf blade abaxially without stellate trichomes, appearing glabrous, with minute multicellular glands, these often embedded on blade, and simple trichomes on veins; nut obovate, flattened at least on 1 side, beak thin, flexible, to 8 mm or more excluding styles. | Castanea dentata |
| 1 | Cupules 2-valved, enclosing 1 flower/fruit; leaf blade abaxially bearing stellate trichomes (occasionally visible only with magnification), often with simple trichomes on veins; nut round in cross section, ovoid-conic, beak less than 3mm excluding styles. | > 2 |
| 2 | Longest spines of cupule often exceeding 10 mm; young twigs glabrous; petiole usually 8–10(–15) mm; bark brownish, moderately to deeply fissured. | Castanea ozarkensis |
| 2 | Longest spines of cupule usually less than 10 mm; young twigs puberulent (sometimes glabrate with age); petiole usually 3–7(–10) mm; bark gray to brown, smooth, not fissured or only shallowly fissured. | Castanea pumila |