Juglans nigra, the eastern black walnut, a species of flowering tree in the walnut family, Juglandaceae, is 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. Isolated wild trees in the upper Ottawa Valley may be an isolated native population or may have derived from planted trees. The black walnut is a large deciduous tree attaining heights of 30 - 40m (98 - 131 ft). Under forest competition, it develops a tall, clear trunk; the open-grown form has a short trunk and broad crown. The bark is grey-black and deeply furrowed. The pith of the twigs contains air spaces. The leaves are alternate, 30 -60 cm long, odd-pinnate with 15 - 23 leaflets, with the largest leaflets located in the center, 7 - 10cm long and 2 - 3cm broad. The male flowers are in drooping catkins 8 - 10cm long, the female flowers are terminal, in clusters of two to five, ripening 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; the seed is relatively small and very hard. The tree tends to crop more heavily in alternate years. Fruiting may begin when the tree is 4 - 6 years old, however large crops take 20 years. Total lifespan of J. nigra is about 130 years. Black Walnut does not leaf out until late spring when the soil has warmed and all frost danger is past. Like other trees of the Fagales order (oaks, hickories, chestnuts, birches, etc.), it has monoecious wind-pollinated catkins. The flowers comprise separate males and females, which do not appear on the same plant at once in order to prevent self-pollination and inbreeding. Thus, two trees are required to produce a seed crop and Black Walnut readily hybridizes with other members of the Juglans genus. While its primary native region is the Midwest and east-central United States, the black walnut was introduced into Europe in 1629. It is cultivated there and in North America as a forest tree for its high-quality wood. 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. Black walnut is primarily a pioneer species similar to red and silver maple and black cherry. It will grow in closed forests, but needs full sun for optimal growth and nut production. Because of this, black walnut is a common weed tree found along roadsides, fields, and forest edges in the eastern US. The wood is used to make furniture, flooring, and rifle stocks, and oil is pressed from the seeds. Nuts are harvested by hand from wild trees. 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 black walnut nutmeats are used as an ingredient in food, while the hard black walnut shell is used commercially in abrasive cleaning, cosmetics, and oil well drilling and water filtration. Where the range of J. nigra overlaps that of the Texas black walnut J. microcarpa, the two species sometimes interbreed, producing populations with characteristics intermediate between the two species. Planting. Black walnut plantings can be made to produce timber, nuts, or both timber and nuts. Patented timber-type trees were selected and released from Purdue University in the early 1990’s. These trees have been sporadically available from nurseries. Varieties include Purdue #1, which can be used for both timber and nut production, though nut quality is poor compared to varieties selected specifically as nut producers. Grafted, nut-producing trees are available from several nurseries operating in the U.S. Selections worth considering include Thomas, Neel #1, Thomas Myers, Pounds #2, Stoker, Surprise, Emma K, Sparrow, S127, and McGinnis. Several older varieties, such as Kwik Krop, are still in cultivation; while they make decent nuts, they would not be recommended for commercial planting. A variety index and characteristics guide is available from Missouri Extension. Pollination requirements should be considered when planting black walnuts. As is typical of many species in Juglandaceae, Juglans nigra trees tend to be dichogamous, i.e.. produce pollen first and then pistillate flowers or else produce pistillate flowers and then pollen. An early pollen-producer should be grouped with other varieties that produce pistillate flowers so all varieties benefit from overlap. Cranz, Thomas, and Neel #1 make a good pollination trio. A similar group for more northern climates would be Sparrow, S127, and Mintle. J. nigra is also grown as a specimen ornamental tree in parks and large gardens, growing to 30 m (98 ft) tall by 20 m (66 ft) broad. It has gained the Royal Horticultural Society's Award of Garden Merit. (3555 1993 H6 Keep Woody Juglans nigra (F)). Food. Black walnut nuts are shelled commercially in the United States. 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 (Ogden, Sparrow, Baugh, Carter and Thomas) showed the most prevalent fatty acid in J. nigra oil is linoleic acid (27.80 - 33.34 g/100g dry kernel), followed (in the same units) by oleic acid (14.52 - 24.40), linolenic acid (1.61 - 3.23), palmitic acid (1.61 - 2.15), and stearic acid (1.07 - 1.69). The oil from the cultivar Carter had the highest mol percentage of linoleate (61.6), linolenate (5.97%), and palmitate (3.98%); the oil from the cultivar Baugh had the highest mol percentage of oleate (42.7%); the oil from the cultivar Ogden has the highest mol percentage of stearate (2.98%). Tapped in spring, the tree yields a sweet sap that can be drunk or concentrated into syrup or sugar. Nut processing by hand. The extraction of the kernel from the fruit of the black walnut is difficult. The thick, hard shell is tightly bound by tall ridges to a thick husk. The husk is best removed when green, as the nuts taste better if it is removed then. Rolling the nut underfoot on a hard surface such as a driveway is a common method; commercial huskers use a car tire rotating against a metal mesh. Some take a thick plywood board and drill a nut-sized hole in it (from one to two inches in diameter) and smash the nut through using a hammer. The nut goes through and the husk remains behind. While the flavor of the Juglans nigra kernel is prized, the difficulty in preparing it may account for the wider popularity and availability of the Persian walnut. Dye. Black walnut drupes contain juglone (5-hydroxy-1, 4-naphthoquinone), plumbagin (yellow quinone pigments), and tannin. These compounds cause walnuts to stain cars, sidewalks, porches, and patios, in addition to the hands of anyone attempting to shell them. The brownish-black dye was used by early American settlers to dye hair. According to Eastern Trees in the Petersen Guide series, black walnuts make a yellowish-brown dye, not brownish-black. The apparent confusion is easily explained by the fact that the liquid (dye) obtained from the inner husk becomes increasingly darker over time, as the outer skin darkens from light green to black. Extracts of the outer, soft part of the drupe are still used as a natural dye for handicrafts. The tannins present in walnuts act as a mordant, aiding in the dyeing process, and are usable as a dark ink or wood stain.

Juglans nigra EN