This is an Excerpt from the Book called “NATIVE TREES FOR NORTH AMERICAN LANDSCAPES ”. Continue reading to learn more about Black Walnut – North American Trees, thanks to the author.
DESCRIPTION: Our most valuable native hardwood lumber comes from one of our most interesting and resilient trees. Black walnut is a tall, strong forest tree of well-drained bottom lands but is seen just as often as a picturesque, weathered survivor in overgrazed pastures or sterile, eroded old fields. Everywhere it grows, humans and squirrels compete for its valuable nut crop, and mature trees in the back forty must be guarded with vigilance against log poachers.
It is rare to see massive old-growth walnuts in their native habitat, with straight trunks clear of limbs for their first 80 feet (24 m), such as those along Sugar Creek in Turkey Run State Park, Indiana. Most old giants in national forests or on private land have already been harvested for their valuable wood. In fact, the largest known black walnut is a planted tree on Sauvie Island, Oregon, more than 1000 miles (1600 km) from its ancestral home. Measured in 1991 at 130 feet (39 m) in height, it is a sprawling, low-limbed tree with a trunk that is 7.4 feet (2.25 m) in diameter. It is probably still alive because its trunk is too short to make a good sawlog.
LEAVES: The highly aromatic, pinnately compound leaves of all our native walnut species look similar, emerge very late in spring, and drop early in fall. Those of black walnut are up to 2 feet (60 cm) long, with paired leaflets and no terminal leaflet. They can turn a good clear yellow early in fall, contrasting nicely with the dark bark, but many trees are defoliated by insects or leaf blights before this happens.
FLOWERS AND FRUIT: Walnuts are close relatives of hickories (Carya), and their flower structures are nearly identical. Staminate catkins are produced in hanging clusters, like green tinsel; pistillate flowers occur singly or in small groups at the ends of twigs.
The fruits ripen in late summer, but many don’t fall until after the first autumn frost. They are among the largest of our native nut-tree fruits; before husking, they occasionally exceed the size of tangerines. The nuts are predictably variable from tree to tree in size, shape, and quality. Lester Cox of Carlinville, Illinois, who has gathered walnuts on his property for years, can examine a nut, tell you which tree it came from, and accurately predict the quality and oil content of each nut based upon the historic performance of that tree.
BEST SEASONS: FALL (for the nut harvest and for the good yellow fall color on disease-resistant specimens). SUMMER (for the open shade and for the aromatic, fernlike foliage).
NATIVE AND ADAPTIVE RANGE: Black walnut grows in scattered groves along the St. Lawrence River, southwest through southern Ontario, and westward to eastern South Dakota, then south throughout most of the eastern United States except for southern coastal areas.
This tree’s performance is closely tied to provenance, and seed sources from local areas or from up to 100 to 200 miles (161 to 322 km) south are recommended. Seeds from more southern sources, when moved north, grow more each year than those from local stock, but the trees are less hardy and more likely to die back in severe winters. Locally adapted black walnut is hardy through most of USDA zone 4
CULTURE: Black walnut is a tough tree that survives with abuse but thrives with proper care. Such care includes full sun and a good, fertile, moist, well-drained soil (limed if too acidic). Black walnut can grow surprisingly quickly under such conditions. It will propagate readily from fall-planted seed, which must be protected from squirrels for the entire first year, and selected trees can be grafted or budded.
Care should be taken to minimize pruning wounds that might serve as entry points for disease, but black walnut is resistant to damage from storms, drought, alkaline soil, and atmospheric ozone. Its deep roots, the long, leafless dormancy period from early fall to late spring, and the light shade cast even in summer promote strong turfgrass growth under its canopy. All native walnut species develop long taproots and can be tough to transplant unless they have been undercut in the nursery.
PROBLEMS: Walnut foliage can be subject to heavy attack by the walnut caterpillar (Datana integerrima) and the related yellowneck caterpillar (D. ministra). These moth larvae feed in groups and arch into a fearsome bluff when disturbed. Target canker (Nectria galligena) is destructive to damaged or weakened trees. The most noticeable disease on some black walnuts is anthracnose, caused by Gnomonia leptostyla. Trees vary in resistance to this leaf spot fungus, which harmlessly but conspicuously defoliates the most susceptible victims in late summer. Many other leaf diseases affect these trees to a lesser extent.
All walnut species and many close relatives manufacture an allelopathic substance called juglone, and none are more potent than black walnut. When the roots of juglone-sensitive plants (including other walnut seedlings) contact walnut roots, they can be stunted or killed. Turfgrasses, most ferns, conifers such as hemlocks (Tsuga) and junipers (Juniperus), and ornamental shrubs like boxwoods (Buxus) and Viburnum species are not usually harmed by juglone. Most of the usual forest tree associates like oaks (Quercus), maples (Acer), hickories (Carya), hackberries (Celtis), ashes (Fraxinus), and beeches (Fagus grandlifolia) are also not severely affected. But juglone is potent against some garden vegetables, apples (Malus) and their relatives, fringe trees (Chionanthus), birches (Betula), azaleas (Rhododendron), and pines (Pinus).
The falling nuts of black walnut can injure the objects or people they and on, and the stain released by their husks is practically impossible to remove from patios. They can also cause litter and mowing problems in closely maintained lawn areas, along with the leaflets and stiff leaf rachises that begin to drop in late summer or early fall.
CULTIVARS: For many years I have admired the lacy, ornamental, slow-growing ‘Laciniata’ at the Morton Arboretum near Chicago. Most other black walnut selections have been directed toward timber or fruit production, and many exist. ‘Lambs Curly’ was chosen not for its fast growth or straightness but for its crooked, curly grains, which is so valuable in the specialty wood trade.
The Northern Nut Growers Association has worked for decades to identify superior trees for nut production throughout the range of the species. Among the best are ‘Cochrane’ from Wisconsion, ‘Edras’ and ‘Grundy’ from lowa, ‘Hare’ from Illinois, ‘Schreiber’ from Indiana, ‘Bowser’ from Ohio, ‘Harney’ and ‘Victoria’ from Kentucky, ‘Norris’ from Tennesse, and ‘Monterey’, ‘Pinecrest’, ‘Thomas’, and ‘Vandersloot’ from Pennsylvania. Although the large-fruited ‘Thomas’ is most frequently offered by nurseries. ‘Pinecrest’and ‘Vandersloot’ reportedly bear even larger nuts. I have selected two more in central Illinois with orange-sized fruits that we use for superior seed sources, but it hardly seems necessary to introduce more walnut selections as cultivars.
SIMILAR AND RELATED SPECIES: Butternut (Juglans cinered), our other-relatively common walnut species, usually a smaller tree. Butternut leaves are complete with a terminal leaflet, unlike those of black walnut. The U.S. national champion grows in a sylvan setting in Chester, Connecticut. It is an exceptional example, standing 78 feet (23.4 m) tall with a trunk nearly 7 feet (2.1 m) thick. The distribution of butternut is more northerly than other native species, but nowhere is it common. It extends north to Quebec City and southern New Brunswick, and many of the finest specimens I have seen have been in Canada. Butternuts hardy in USDA zone 3. It is more particular about soil than black walnut and will not succeed on a poor or dry site, through t tolerates rocky soil. Nut crops can be sporadic due to the sensitivity of the pistillate flowers to frost, even when the staminate catkins develop normally.
Butternut blight is a fatal disease caused by a fungus named Sirococcus clavigignenti-juglandacearum, which forms cankers later invaded by another fungus. Melanconis juglandis. These organisms are as difficult to cure as they are to pronounce, and eventually the tree dies. This disease is spreading throughout the natural range of butternut, even into Ontario, and the tree may be on the road to extinction unless a cure is found.
Of the four other walnuts native to North America, two can be grown in the warmer portions of our area: Arizona walnut (Juglans major), from Arizona and western New Mexico, and nogalito (J. microcarpa), or little walnut, from Oklahoma, Texas, and New Mexico. They make beautiful specimens in desert canyons of the Southwest and very tolerant of alkaline soils. Both may be grown at least as far north as USDA zone 6 under the right soil conditions, and they have very small fruits that are much less painful when landing on your head. The record (Arizona walnut is 73 feet (21.9 m) tall and nearly 6 feet (1.8 m) thick. Nogalito is smaller, with a U.S. national champion in Texas that is 50 feet (15 m) tall and slightly more than 4 feet (1.2 m) in diameter. It is particularly fine in texture for a walnut and is useful in small landscapes that might not have room for a larger walnut species. The other two native North American walnut species are confined to California.
About fourteen additional species are found in other parts of the world, including some commercially productive nut-orchard species. Of these, by far the most well known is Persian walnut (Juglans regia), also known as European walnut, sold in stores and grown in parts of North America for nut production.
COMMENTS: Black walnut is a preferred host of the beautiful luna moth and the immense regal moth (including its awe-inspiring larva, the hickory horned devil), which can be 6 inches (15 cm) across. Once seen, neither can be forgotten. Black walnut also hosts the larva of the walnut sphinx moth, unusual for the squeaking sound it makes. Nutmeats of black walnut and butternut are used commercially for oil and flavoring, and on the farm for walnut bread and other delights. Birds pick through the debris left behind when humans shell out walnuts, but they are unable to crack whole walnuts without help. The shells are extremely hard, so squirrels and chipmunks seem unique among wildlife in being to gnaw through them.
Some creative uses have been devised for walnut. Dried walnut leaves can be mixed with straw as a flea repellent in animal bedding. Ground walnut shells have been used as specialty abrasives in sandblasters to polish metals. Some orchardists who grow Persian walnuts commercially graft them high on black walnut under stocks; when production peaks out and the trees are removed, each tree has developed a high-quality, marketable black walnut veneer log at its base.
Butternuts are so tasty that Native Americans planted them for a food source. One tree that was probably planted for this purpose, a state champion in Poughkeepsie, New York, was rescued from destruction in 2001 by a heroic effort of the Forbus Butternut Association, a neighborhood association of concerned citizens. They raised enough money to buy the vacant city block, where the tree had lived for centuries, from the developer who planned to remove it for construction of a subdivision.
On a much broader scale, the U.S. Forest Service is leading an interagency effort to solve the butternut blight problem through research and identification of resistant trees. If you know of mature, healthy butternut trees in an area where butternut blight is established, you can help by reporting their location to the Forest Service or to your state or provincial natural resource agency for possible use in resistance-selection breeding programs.
