Flora of North America species comparison

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Castanea

chestnut, châtaignier
Habit Trees or shrubs, winter-deciduous, sometimes rhizomatous.
Leaves

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.
Terminal

buds absent, pseudoterminal bud (axillary bud of youngest leaf) ovoid, with 2 unequal opposite outer scales enclosing several imbricate inner scales.
x

= 12.

Castanea
Distribution
from USDA
North America; Europe; Asia
[BONAP county map]
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.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
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.
C. 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.
C. 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.
C. pumila
Source FNA vol. 3.
Parent taxa Fagaceae
Subordinate taxa
C. dentata, C. ozarkensis, C. pumila
Name authority Miller: Gard. Dict. Abr. ed. 4. (1754)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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