2. Juglans nigra L. (black walnut, eastern black walnut)
Pl. 431 l–n; Map
1933
Plants trees to
35 m tall (to 50 m elsewhere). Bark medium to dark gray or brown, deeply split
into narrow, rough ridges. Pith light brown. Terminal buds 8–10 mm long, ovoid
or subglobose, weakly flattened. Leaf scars with the upper margin notched,
glabrous or sometimes velvety, but never forming a prominent velvety ridge.
Leaves 20–60 cm long, the petiole 6.5–14.0 cm long, glandular-hairy, with
(9–)15–19(–23) leaflets, sometimes including a small terminal leaflet. Leaflets
(3–)6–15 cm long, 1.5–5.5 cm wide, lanceolate to narrowly ovate, more or less
symmetrical or slightly arched (appearing slightly asymmetrically tapered),
rounded to shallowly cordate (sometimes asymmetrically so) at the base, tapered
at the tip, the margins finely toothed, yellowish green to green, the upper
surface with scattered gland-tipped hairs and fasciculate hairs only along the
midvein, the undersurface with moderate to abundant unbranched or 2-branched
hairs (the branches appearing fasciculate) on and between the veins. Staminate
catkins 5–10 cm long, the staminate flowers with 17–50 stamens, the anthers
0.8–0.9 mm long. Fruits usually solitary or paired, 4–8 cm long, subglobose to
globose or rarely ellipsoid, the husk somewhat warty to nearly smooth, with
scattered gland-tipped hairs and dense, minute scales, remaining fleshy or
becoming somewhat leathery with age. Nuts 3–4 cm long, subglobose to globose or
rarely ellipsoid, with numerous, irregular, rounded, longitudinal grooves and
coarsely warty between the grooves. 2n=32. April–May.
Scattered to
common nearly throughout the state (eastern U.S. west to North Dakota and
Texas; Canada; introduced farther west). Bottomland forests, mesic upland
forests, bases of bluffs, and banks of streams and rivers; also margins of
pastures and crop fields, railroads, and roadsides.
Black walnut is
one of the premier hardwood timbers of North America. The nuts are a minor
trade item; they surely would be used heavily if it were not so difficult to
extract the nutmeat from the thick shell. In 1990, the Missouri legislature
officially designated the eastern black walnut as the state nut, although at
least one senator was of the opinion that this measure proved that Missouri had
197 state nuts sometimes also known as legislators (V. Young, 1990). The
process of shelling the nuts (removing the husks) produces a strong unpleasant
odor and stains the hands.
Walnut trees
frequently have few plants growing close-by. A quinone compound known as
juglone is produced mainly by the roots and fruit husks and has a strong allelopathic
effect, inhibiting the establishment and growth of many other plant species
(for a review, see Rice, 1984).
Plants with
ellipsoidal fruits have been called f. oblonga (Marsh.) Fernald.