Black Walnut
Juglans nigra L.
Noyer noir
Uncommon in Canada, occurring naturally in southern Ontario and frequently planted as an ornamental in its range. Found in eastern Canada and southern British Columbia (Zones CA3, NA4).
Leaves:
14-22 short-stalked leaflets (15-23 with terminal leaflet), on a moderately stout central stalk, 20-60 cm long.
Yellowish-green and smooth above, faintly hairy beneath.
Terminal leaflet is missing or much smaller than the largest lateral leaflets.
Middle leaflets are larger than those at either end of the leaf.
Buds:
Terminal bud ovoid, slightly flattened, 8-10 mm long, blunt, pale gray, and slightly hairy.
Leaf scars are deeply notched on the upper margin, hairless.
Twigs:
Stout, orange-brown, faintly hairy.
Pith is orange-yellow.
Flowers:
Pollen flowers in catkins, 5-10 cm long, with 20-30 stamens.
Seed flowers in erect clusters of 1-4.
Fruits:
Globular, 4-6 cm in diameter, in drooping clusters of 1-3.
Husk is slightly hairy.
Nut surface with deep grooves and smooth-topped ridges.
Kernel is strongly flavored and oily.
Bark:
Light brown and scaly when young.
Becomes darker with rounded, almost black, intersecting ridges as it matures.
Wood:
Heavy, hard, strong, dark brown to black, with nearly white sapwood.
Resistant to decay and straight-grained.
Size and Form:
Medium-sized trees, up to 30 m high, 120 cm in diameter, and 150 years old.
Trunk is straight.
Crown is open and rounded, with a few large ascending branches.
Root system is deep and wide-spreading, usually with a taproot.
Habitat:
Grows in well-drained, fertile lowlands.
Found singly or mixed with other broadleaf trees.
Intolerant of shade.
Notes:
Valued for its wood, which is easily worked and finished, does not shrink or warp, and has an attractive grain.
Isolated stands in the Ottawa Valley may be planted or remnants of warmer climates.
Toxic substance, juglone, leaches from fallen leaves and is exuded by roots; it inhibits the growth of many broadleaf plants, including walnut seedlings.
Quick Recognition:
Leaves slightly hairy beneath, terminal leaflet small or missing (vs. butternut’s normal-sized terminal leaflet).
Leaf scar notched and not hairy (vs. butternut’s flat, hairy leaf scar).
Fruit is globular with smooth-topped ridges (vs. butternut’s elongated fruit with jagged ridges).