21. Quercus prinoides Willd. (dwarf chestnut oak)

Pl. 416 c; Map 1859

Plants shrubs, 0.5–3.0(–5.0) m tall. Bark light ashy gray, divided into loose plates, blocks, or strips. Twigs 1.0–2.5 mm wide, orangish brown to reddish brown or grayish, glabrous or with branched spreading hairs. Buds 2–4 mm long, reddish brown or grayish, the scales glabrous or sparsely pubescent, usually hairy along the margins. Petioles 5–21 mm long. Leaf blades 7–13 cm long, 2.7–6.5(–9.0) cm wide, relatively thin and flexible, obtuse or rounded at the base, divided 10–25% of the width, the coarse scallops 6–9 per side, equal or slightly shallower above the midpoint; well-developed scallops rounded or rounded-obtuse, undivided; secondary veins 6–9 per side, each (except the basalmost) reaching the margin at the tip of a scallop; the upper surface rather dull, glabrous or nearly so (with a few inconspicuous, 4–8-rayed, spreading or appressed hairs), the undersurface white or sometimes pale green, covered (usually very densely so) with mostly 7–15-rayed, stellate hairs and sometimes also 5–7-rayed, spreading hairs (with rays 0.2–0.4 mm long), usually more or less felty to the touch. Acorn stalks 1–7 mm long, the cup 6–11 mm long, 12–19 mm wide, covering 40–50% of the nut, hemispheric or bowl-shaped, the outer surface with the scales 1.5–3.0 mm long, those near the cup margin not differentiated. Nuts 10–18 mm long, 9–12 mm wide, cylindric to ovoid or ellipsoid. April–May.

Scattered mostly in the western half of the state (eastern U.S. west to Nebraska and Oklahoma; Canada). Upland prairies, loess hill prairies, glades, savannas, openings of dry upland forests, and tops of bluffs; also roadsides.

For a discussion of the problems in separating Q. prinoides from the closely related Q. muehlenbergii, see the treatment of that species. Hybridization between the two is also discussed in the treatment of Q. muehlenbergii. In Missouri, hybrids involving Q. prinoides and three other oak species have been documented.