12. Quercus shumardii Buckley (Shumard oak)

Quercus shumardii var. schneckii (Britton) Sarg.

Quercus shumardii var. stenocarpa Laughlin

Pl. 415 c, d; Map 1850

Plants trees to 35 m tall. Bark medium to dark gray, divided into narrow persistent ridges, the inner bark pinkish. Twigs 2.0–3.5 mm wide, yellowish brown, grayish brown, or dark brown, glabrous. Buds 4–8 mm long, brown to grayish brown or sometimes dark brown, glabrous. Petioles 25–72 mm long. Leaf blades 11–17 cm long, 8–18 cm wide, truncate or broadly obtuse at the base, divided (50–)60–90% of the width, the lobes 3 or 4 per side, the largest lobes at or above the midpoint; well-developed lobes 25–60 mm wide, obovate and broadened outward (usually strongly so), rarely ovate, acutely angled or tapered apically, rarely rounded-obtuse, with several teeth, 1 or 2 secondary lobes on the lower margin and 0 or 1 on the upper margin, each with 5–12 bristles 2–5 mm long (the whole blade with 25–60 marginal bristles); the strongest secondary veins reaching the margin at the tips of the lobes and ending in bristles, others reaching toward sinuses and turning aside before reaching the margin; the upper surface glossy, glabrous, the undersurface green, glabrous or rarely with inconspicuous, unbranched, appressed hairs, smooth to the touch, the vein axils with prominent tufts of 7–15-rayed, stalked hairs. Acorn cups 5–14 mm long, 12–24 mm wide, covering 20–50% of the nut, saucer- or bowl-shaped, the inner surface smooth, glabrous or with a few hairs near the nut scar, the outer surface with the scales mostly distinctly convex-thickened at the base, sparsely pubescent. Nuts 14–27 mm long, 11–19 mm wide, ovoid or almost cylindric, without concentric grooves around the tip. April–May.

Scattered in the southern 2/3 of the state (eastern U.S. west to Nebraska and Texas; Canada). mesic to dry upland forests, savannas, edges of glades, tops of bluffs, banks of streams and rivers, and rarely margins of fens.

Forms with the acorn cup deeply bowl-shaped have been called var. schneckii. Steyermark (1963) noted that in Missouri such plants tend to occupy sites at the dry end of the ecological spectrum of the species. However, Hess and Stoynoff (1998) noted that the type of var. schneckii originated from a bottomland site in southern Illinois, and they could not distinguish trees at the type locality of this segregate from typical var. shumardii. Similarly, Laughlin (1969) segregated var. stenocarpa to distinguish large trees in Missouri and Illinois having ellipsoid acorns with very shallow cups. Another variant that most botanists currently treat as a separate species is Quercus acerifolia (E.J. Palmer) Stoynoff & W.J. Hess (Q. shumardii var. acerifolia E.J. Palmer), maple-leaved oak, which differs in its nearly palmately compound leaves that are mostly wider than long. Although this taxon currently is thought to be endemic to west-central Arkansas, some specimens of Q. shumardii from southwestern Missouri come close to it in their leaf lobing pattern and dimensions. Morphological variation within this species complex requires further study before such variants can be recognized with confidence. It seems likely that in the future new data from molecular or other sources will result in a refinement of the taxonomy of Q. shumardii and its variants. Potentially complicating the issue is the fact that hybrids with four other oak species have been documented from Missouri.