7. Quercus nigra L. (water oak)
Pl. 414 e, f;
Map 1845
Plants trees to
30 m tall. Bark medium gray, divided into low persistent ridges, the inner bark
pinkish. Twigs 1–2 mm wide, dark brown, glabrous. Buds 3–5 mm long, dark brown
or grayish, pubescent or the lower scales glabrous. Petioles 2–10 mm long. Leaf
blade 5–11 cm long, 1.6–6.0 cm wide, narrowly angled to long-tapered at the
base, divided shallowly or up to 70% of the width, the lobes 1(2) per side, the
largest lobes above midpoint, often near the blade tip, even well-developed
lobes usually a mere convexity on the leaf margin, if distinct then 10–20 mm
wide, oblong or ovate, broadly rounded, undivided or with a distinct bulge on
the lower margin, each with 0(–2) bristles 0.5–1.0 mm long (the whole blade
with 0–7 marginal bristles), the secondary veins turning aside before reaching
the margin or with 1 pair reaching the margin at the tips of the lobes and
ending in bristles; the upper surface rather dull, glabrous, the undersurface
green, glabrous or with inconspicuous unbranched appressed hairs, smooth to the
touch, the vein axils with prominent tufts of 6–12-rayed, stalked hairs. Acorn
cups 4–6 mm long, 13–14 mm wide, covering 20–40% of the nut, saucer-shaped to
shallowly bowl-shaped, the inner surface smooth, hairy except near the rim, the
outer surface with the scales tending to be distinctly convex-thickened at the
base, pubescent. Nuts 11–13 mm long, 13–14 mm wide, depressed-ovoid, without
concentric grooves around the tip. 2n=24. April–May.
Scattered in the
Mississippi Lowlands Division (southeastern U.S. west to Missouri, Oklahoma,
and Texas). Swamps, bottomland forests, banks of streams and rivers, and
margins of lakes, oxbows, and sloughs; also ditches and fencerows.
Leaves of Q.
nigra are quite variable morphologically and a number of forms have been
described from material in other states to account for extremes in variation.
Juvenile leaves or leaves from vigorous sprouts may be deeply lobed. A specimen
from Dunklin County (Holmes 981, at the Missouri Botanical Garden
Herbarium) appears to represent a hybrid with either Q. palustris or Q.
texana, but the parentage cannot be confirmed. Other hybrids in Missouri
appear to be quite uncommon, only Q. falcata and Q. phellos have
been recorded to hybridize with Q. nigra in the state.