9. Quercus palustris Münchh. (pin oak)

Pl. 414 a, b; Map 1847

Plants trees to 25 m tall. Bark medium to dark gray, divided into low persistent ridges, the inner bark pinkish. Twigs 1.5–3.5 mm wide, dark reddish brown, glabrous (rarely with scattered hairs). Buds 2.0–6.5 mm long, tan or brown, glabrous except along the margins. Petioles 15–52 mm long. Leaf blades 8.5–20.0 cm long, 6–23 cm wide, truncate to obtuse or sometimes tapered at the base, divided 70–90% of the width, the lobes 2 or 3(4) per side, evenly spaced or the lowest closer together, the second pair from the base the largest; well-developed lobes 10–33(–40) mm wide, oblong or tapered, seldom much broadened outward, narrowly tapered or sometimes merely acute apically, with a few teeth and sometimes a secondary lobe on each margin, each with 3–9 bristles 3–9 mm long (the whole blade with 17–38 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 usually rather shiny, glabrous or with scattered hairs on the major veins, the undersurface green, glabrous, smooth to the touch, the vein axils with prominent tufts of 11–19-rayed, stalked hairs. Acorn cups 3–6 mm long, 12–19 mm wide, covering 10–30% of the nut, saucer-shaped, the inner surface regularly dimpled, the central portion hairy, the outer surface with the scales thin and plane, pubescent. Nuts 9–15 mm long, 10–15 mm wide, short-ovoid, without concentric grooves around the tip. 2n=24. April–May.

Common nearly throughout the state (eastern [mostly northeastern] U.S. west to Wisconsin, Nebraska, and Oklahoma; Canada). Bottomland forests, swamps, banks of streams, rivers, and spring branches, margins of ponds, lakes, sinkhole ponds, oxbows, and sloughs, and occasionally mesic upland forests; also fencerows, edges of pastures, and roadsides.

Hybrids between Q. palustris and six other oaks have been documented from Missouri.

Pin oak is a common street tree in some cities, as it tends to grow somewhat more quickly than most other red oak species. However, in areas with soils having high pH the leaves can yellow, so care must be taken periodically to acidify such soils.