19. Quercus michauxii Nutt. (swamp chestnut oak, basket oak, cow oak)

Pl. 416 a, b; Map 1857

Plants trees to 35 m tall. Bark light ashy gray, divided into loose plates or strips, or ± persistent ridges on old trunks. Twigs (1.0–)2.0–3.5 mm wide, grayish brown to brown, glabrous, finely hairy, or occasionally with a few branched, spreading hairs. Buds 4–7 mm long, reddish brown, finely short-hairy. Petioles 6–33 mm long. Leaf blades 13–21 cm long, 6.5–13.0 cm wide, relatively thin and flexible, obtuse, rounded, or truncate at the base; divided 10–20% of the width, the coarse scallops 11–14 per side, smaller toward the blade tip; well-developed scallops rounded or rounded-obtuse, undivided; secondary veins 12–17 per side, each (except the basalmost) reaching the margin at the tip of a scallop; the upper surface dull or somewhat shiny, glabrous or with scattered, 1–7-rayed, spreading hairs, the undersurface green or pale, sparsely to densely covered with 1–7-rayed, spreading hairs, never with appressed-stellate or unbranched appressed hairs, usually very felty to the touch. Acorn stalks 10–23 mm long, the cup 13–19 mm long, 24–33 mm wide, covering 30–50% of the nut, hemispheric, the outer surface with the scales 3–5 mm long, those near the cup margin not differentiated. Nuts 20–30 mm long, 15–24 mm wide, ovoid or ellipsoid. 2n 24 (reported as by Friesner [1930]). April–May.

Scattered in the Mississippi Lowlands Division and adjacent portions of the Ozarks and Ozark Border (eastern [mostly southeastern] U.S. west to Missouri, Oklahoma, and Texas). Bottomland forests, swamps, and banks of streams and rivers.

The name Q. prinus L. has been used at times for either for Q. michauxii or Q. montana Willd. (Hardin, 1979). In view of its persistent use for more than one species, Whittemore and Nixon (2005) proposed that it be formally rejected from further use.

The wood of Q. michauxii is of high quality, and it has the sweetest acorns (with the lowest tannin concentration) of any Missouri oak. Because of this, cows relish the acorns, giving rise to the common name cow oak. Because the wood tends to split naturally into long narrow strips, it was used in basketry in some of the southeastern states (Steyermark, 1963), hence the common name basket oak. In Missouri, hybrids have been recorded involving Q. michauxii and three other species.