Eastern black walnut

Appearance

*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 . 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 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 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 long and 2–3 cm broad. The leaflets have a rounded base and a long pointed 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
⤷ Flowers Black walnut is monoecious. The male flowers are in drooping catkins 8–10 cm long. These are borne from axilary buds on the previous year's growth. The female flowers are terminal, in clusters of two to five on the current year's growth.
⤷ Fruit Ripens during the autumn into a fruit with a brownish-green, semifleshy husk and a brown, corrugated nut. The whole fruit, including the husk falls in October; the seed is relatively small and very hard.

The fruit production tends to occur irregularly with some years producing larger crops than others . Fruiting may begin when the tree is 4–6 years old, but large crops take 20 years. Total lifespan of ''J. nigra'' is about 130 years. Like other trees of the order Fagales, such as oaks, hickories, chestnuts, and birches, it is monoecious, with wind-pollinated catkins. Male and female flowers are in separate spikes, and the female flowers typically appear before the male on a single tree . As a consequence, self-pollination is unlikely. However, individual trees are commonly self-compatible; if they are not pollinated by neighboring trees, they may set self-fertilized seeds. For maximum seed germination, the seeds should be cold-moist stratified for 3–4 months, although the exact time depends on the seed source. The seedlings emerge in April or May. While most trees with taproots have a reputation for slow growth, black walnut is an exception and can achieve very rapid growth in the seedling stage, typically 90 cm their first year and even more in the 2nd year. Black walnut has one of the shortest growing seasons of any tree native to the eastern US. Leafout varies from early April in the southernmost extent of its range to early June in the northern extent.

Black walnut has a strong taproot, which makes the seedlings resilient, but difficult to transplant.

Black walnut is more resistant to frost than the English or Persian walnut, but thrives best in the warmer regions of fertile, lowland soils with high water tables, although it will also grow in drier soils, but much more slowly. Some soils preferred by black walnut include Alfisol and Entisol soil types. Walnut grows best on sandy loam, loam, or silt loam type soils but will also grow well on silty clay loam soils. It prefers these soils because they hold large quantities of water which the tree draws from during dry periods.

Visually, black walnut is similar to the butternut in leaf shape, and the range also overlaps significantly. The fruits are quite different, and their presence makes an identification easy, as black walnut fruits are round and butternuts are more oval-oblong shaped. When a fruit is not available, two species can be differentiated based on the leaf scars, or the place where the leaf meets the stem: butternut has a leaf scar with a flat upper edge and with a velvety ridge above that flat part, but black walnut has an indented leaf scar with no hairy ridge.

Habitat

Black walnut is primarily a pioneer species similar to red and silver maple and black cherry. Because of this, black walnut is a common weed tree found along roadsides, fields, and forest edges in the eastern US. It will grow in closed forests, but is classified as shade intolerant; this means it requires full sun for optimal growth and nut production.

Black walnut's native range extends across much of the eastern US. It is absent from the coastal plain south of North Carolina as well as the Mississippi Valley, and does not occur in the northern tier of the eastern US, where the frost-free season is too short for the nuts to develop. Its western range extends all the way to the eastern Great Plains, after which climate conditions become too dry for it.

Black walnut is one of the most abundant trees in the eastern US, particularly the Northeast, and its numbers are increasing due to epidemics that have affected other tree species, including emerald ash borer, chestnut blight, butternut canker, wooly hemlock adelgid, dogwood anthracnose, Dutch elm disease, and Gypsy moth infestations. Widespread clear-cutting of oaks due to Gypsy moth damage in the 1970s-80s particularly aided in the tree's spread. The aggressive competitive strategy of black walnut such as its fast growth, alleopathic chemicals, and rodent-dispersed seeds, have also contributed.

The nuts are food for many rodents and make up to 10% of the diet of eastern fox squirrels. The nuts are also eaten by species of birds. The leaves are browsed by white tailed deer, although they are not a preferred food. Squirrels benefit this species by distributing and burying the seeds; if the seeds are not reclaimed by the squirrel, they will germinate and help disperse the species.

Where the range of the eastern black walnut overlaps that of the Texas black walnut , the two species sometimes interbreed, producing populations with characteristics intermediate between the two species. ''J.nigra'' and ''J. cinerea'' often grow in the same range as well but they do not hybridize naturally.

The tree's roots often form endomycorrhizal relationships with fungi in the genus ''Glomus''. Some endomycorrhizal relations improve the plant's growth.

Species often associated with ''J. nigra'' include yellow-poplar , white ash , black cherry , basswood , American beech , sugar maple , oaks , and hickories . Near the western edge of its range, black walnut may be confined to floodplains, where it grows either with American elm , common hackberry , green ash , and boxelder , or with basswood and red oak on lower slopes and other favorable sites.

Food

Black walnut nuts are shelled commercially in the United States. About 65% of the annual wild harvest comes from the U.S. state of Missouri, and the largest processing plant is operated by Hammons Products in Stockton, Missouri. The nutmeats provide a robust, distinctive, natural flavor and crunch as a food ingredient. Popular uses include ice cream, bakery goods and confections. Consumers include black walnuts in traditional treats, such as cakes, cookies, fudge, and pies, during the fall holiday season. The nuts' nutritional profile leads to uses in other foods, such as salads, fish, pork, chicken, vegetables and pasta dishes.

Nutritionally similar to the milder-tasting English walnut, the black walnut kernel is high in unsaturated fat and protein. An analysis of nut oil from five named ''J. nigra'' cultivars showed the most prevalent fatty acid in ''J. nigra'' oil is linoleic acid , followed by oleic acid , linolenic acid , palmitic acid , and stearic acid . The oil from the cultivar Carter had the highest mol percentage of linoleate , linolenate , and palmitate ; the oil from the cultivar Baugh had the highest mol percentage of oleate ; the oil from the cultivar Ogden has the highest mol percentage of stearate .

Tapped in spring, the tree yields a sweet sap that can be drunk or concentrated into syrup or sugar that is not unlike the sap of sugar maple.

Uses

Walnut, black Black walnutNutritional value per 100 gramsEnergy2,586 kJ Carbohydrates9.91 gStarch0.24 gSugars1.10 gDietary fiber6.8 g
Fat59.00 gSaturated3.368 gMonounsaturated15.004 gPolyunsaturatedomega‑3omega‑635.077 g2.006 g33.072 g
Protein24.06 g