Juglans nigra

The tree grows to tall. Under forest competition, it develops a tall and straight trunk. When grown in an open area it has a short trunk and broad crown. The buds are pale silky and covered in downy hairs. The terminal buds are ovate, and long, and slightly longer than broad, the lateral buds are smaller and superposed. 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. The leaf scar has three prominent bundle scars and has a notch on the side that points toward the tip of the branch (distal side). Black walnut is monoecious. The male (staminate) flowers are in drooping catkins long. These are borne from axillary 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. During the summer/autumn, a spherical fruit (nut) ripens. It comprises 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. 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. == Distribution and habitat ==

The species is native to 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. The range of the black walnut is strongly correlated with low maximum vapour-pressure deficit. == Ecology ==

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, beyond 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 spongy moth infestations. Widespread clear-cutting of oaks due to spongy moth damage in the 1970s–1980s 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, J. nigra and J. cinerea often grow in the same range as well but they do not hybridize naturally. However, infestations of maggots are undesirable because they make the husk difficult to remove and are unsightly. Maggots can be serious for commercial walnut growers, who tend to use chemical treatments to prevent damage to the crop. Some non-chemical controls also exist, such as removing and disposing of infested nuts. The walnut weevil (Conotrachelus retentus) grows to long as an adult. The adult sucks plant juices through a snout. The eggs are laid in fruits in the spring and summer. Many nuts are lost due to damage from the larvae, which burrow through the nut shell. Black walnut is affected by European canker (Neonectria galligena). The infection spreads slowly but infected trees eventually die. Important leaf sucking insects include species of aphids and plant lice including (Monellia spp. and Monelliopsis spp.), which suck the juices from leaves and often deposit a sticky substance called "honey-dew" on the leaf surface that may turn black and prevent photosynthesis; and the walnut lace bug (Corythucha juglandis), which causes damage when the adults and nymphs suck the sap from the lower surfaces of walnut leaflets. This disease has recently been discovered in Tennessee, and could potentially have devastating effects on the species in the eastern United States. Vectored by the walnut twig beetle (Pityophthorus juglandis), a fungus, Geosmithia morbida, spreads into the wood around the galleries carved by the small beetles. The fungus causes cankers that inhibit the movement of nutrients in black walnut, leading to crown and branch dieback, and ultimately death. Allelopathy While black walnut is considered allelopathic, meaning it excretes chemicals into its environment that harm competition, research from 2019 has questioned whether this long-held belief holds up to scientifically rigorous examination. Many publications that have repeated claims of black walnut allelopathy cite a very limited set of dated research literature, which has not held up to scientific scrutiny. Anecdotally, records of walnut toxicity to other plants have been observed as far back as the first century when Pliny the Elder wrote: "The shadow of walnut trees is poison to all plants within its compass." Like other walnuts, the roots, inner bark, nut husks, and leaves contain a nontoxic chemical called hydrojuglone; Even after a tree is removed the soil where the roots once were will still contain juglone for several years after the tree is removed as more juglone will be released as the roots decay. Interaction with horses Horses are susceptible to laminitis from exposure to black walnut wood in bedding. ==Cultivation==

The fruit production tends to occur irregularly with some years producing larger crops than others (see mast year). 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 (dichogamy). 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. While its primary native region is the Midwest and east-central United States, the black walnut was introduced into Europe, likely in the year 1629, where it has gained economic significance. It is also cultivated in Hawaii. Pollination requirements should be considered when planting black walnuts. As is typical of many species in Juglandaceae, J. nigra trees tend to be monoecious, 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. Sometimes black walnut is planted as part of reclaiming mines. the U.S. state of Missouri is home to the world's largest processor and distributor of black walnuts, which the Missouri Department of Conservation considers to be the state's most valuable timber. In 1990, Missouri named the "Eastern Black Walnut" as its official tree nut. Missouri's largest processing plant is operated by Hammons Products in Stockton, Missouri. NPR affiliate KCUR stated in an article that "Ralph Hammons began the company in 1946 with a nut cracking machine acquired from Tennessee." The Stockton Black Walnut Festival, which has been held annually since 1961, "brings the community together for a 3-day event jam-packed with activities including a carnival, tractor pull, nut roll and 2-hour parade," stated Alexa Hodges in a VOX article. Nut processing by hand (right) 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. 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. American pioneers let the nuts dry in the sun, then removed the husks and let the kernels dry—making them less bitter. 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 English walnut. Ornamental J. nigra is also grown as a specimen ornamental tree in parks and large gardens, growing to tall by broad. It has gained the Royal Horticultural Society's Award of Garden Merit. ==Uses==

As food Black walnut kernels are edible. The nut provides a robust, distinctive, natural flavor and crunch as a food ingredient. Common 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 are versatile for uses in other foods, such as salads, fish, pork, chicken, vegetables and pasta dishes. 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. Nutrition Black walnut kernels are 5% water, 59% fat, 24% protein, and 10% carbohydrates. In a reference amount of , walnuts supply 619 calories and several micronutrients in "rich" amounts (20% or more of the Daily Value, DV), including the dietary minerals manganese (169% DV) and copper (156% DV), among others, and the B vitamins, B6 (34% DV) and pantothenic acid (33% DV). Black walnut kernels are a moderate source (10–19% DV) of vitamin E and riboflavin. Analysis of black walnut fat content showed the most prevalent fatty acids are linoleic acid (33.8%), followed by oleic acid (15.3%), alpha-linolenic acid (2.7%), palmitic acid (1.9%), and stearic acid (1.5%). 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. Shells Walnut shells are often used as an abrasive in sand blasting or other circumstances where a medium hardness grit is required. The hard black walnut shell is also used commercially in abrasive cleaning, a filtering agent in scrubbers in smoke stacks, cleaning jet engines, cosmetics, and oil well drilling and water filtration. which makes it less dense than oak. == Largest trees ==

The U.S. national champion black walnut is on a residential property on Sauvie Island, Oregon. It is diameter at breast height and tall, with a crown spread of . , Oregon. The tallest black walnut in Europe is located in the Woluwe Park in the city of Sint-Pieters-Woluwe, Brussels, Belgium. It has a circumference of , height of exactly (measured by laser), and was planted around 1850 (± 10 years). The largest black walnut in Europe is located in the Castle Park in the city of Sereď, Slovakia. It has a circumference of , height of and estimated age of 300 years. == See also ==