The black walnut tree used to be a staple in everyone’s backyard orchard planted along with apple and peach trees. The nuts from this tree have a stronger taste than its English Walnut cousin and are more difficult to harvest. Years ago, black walnuts would be spread out on top of farm sheds to hasten their ripening. When the nuts have turned completely black, they are easier to shuck. But be careful! As the nuts ripen, they are filled with a dark black fluid which will stain everything. The liquid was once used as ink and is still used as a natural dye.
Juglans nigra, the eastern black walnut, is a species of deciduous tree in the walnut family, Juglandaceae, native to eastern North America. It grows mostly in riparian zones, from southern Ontario, west to southeast South Dakota, south to Georgia, northern Florida and southwest to central Texas. Wild trees in the upper Ottawa Valley may be an isolated native population or may have derived from planted trees.
Black walnut is an important tree commercially, as the wood is a deep brown color and easily worked. The fruits, walnuts, are cultivated for their distinctive and desirable taste. Often, trees are grown for both lumber and walnuts simultaneously and many cultivars have been developed for improved quality nuts or wood. Black walnut is currently under pressure from the thousand cankers disease that is causing decline of walnuts in some areas. Black walnut is also allelopathic, which means that it releases chemicals from roots and other tissues that harm other organisms and give the tree a competitive advantage; this is often undesirable as it can harm garden plants and grasses.
Odor Most parts of the tree including leaves, stems, and fruit husks have a very characteristic pungent or spicy odor. This odor is lacking in the nut itself.
Trunk Height 30–40 m (100–130 ft). Under forest competition, it develops a tall and straight trunk. When grown in an open area it has a short trunk and broad crown.
Bark The bark is typically grey-black and deeply furrowed into thin ridges that gives the bark a diamond shaped pattern.
Pith The pith of the twigs is chambered and light brown.
Buds The buds are pale silky and covered in downy hairs. The terminal buds are ovate, and 8 mm (5⁄16 in) long, and slightly longer than broad, the lateral buds are smaller and superposed.
Leaves The leaves are compound and alternately arranged on the stem. They are 30–60 cm (1–2 ft) long, typically even-pinnate but there is heavy variation among leaves. The stems have 15–23 leaflets, with the largest leaflets located in the center, 7–10 cm (2 3⁄4–4 in) long and 2–3 cm (3⁄4–1 1⁄4 in) broad. The leaflets have a rounded base and a long pointed (acuminate) tip as well as having a serrated edge. The leaves are overall dark green in color and are typically hairy on the underside.
Leaf scar The leaf scar has 3 prominent bundle scars and has a notch on the side that points toward the tip of the branch (distal side)
Flowers Black walnut is monoecious. The male (staminate) flowers are in drooping catkins 8–10 cm (3 1⁄4–4 in) long. These are borne from axilary buds on the previous year’s growth. The female (pistillate) flowers are terminal, in clusters of two to five on the current year’s growth.
Fruit Ripens during the autumn into a fruit (nut) with a brownish-green, semifleshy husk and a brown, corrugated nut. The whole fruit, including the husk falls in October or November; the seed is relatively small and very hard.