Butternut looks a lot like its close relative, black walnut, with compound leaves featuring 11 to 17 oval leaflets with serrated edges. The bark is more gray and less fissured than the black walnut, and the nuts are more oval and less rounded than the fruit of the black walnut. Butternut tree forms a broadly rounded crown that serves well to provide shade in the landscape; the crown can hang quite low if the tree is not kept pruned. Yellowish-green flowers appear in late spring, giving way to the fruits that ripen into nuts in fall. The fall color is a fairly unremarkable yellow. Butternut trees are normally planted in spring or fall from potted nursery saplings, ball-and-burlap specimens, or bare-root trees. They are fairly slow-growing trees, adding less than 12 inches per year. Because they have deep taproots, it is quite hard to move butternuts once they are established. In the right location, they will live happily for as much as 75 years. Because of its susceptibility to canker disease, this tree is grown mostly by native plant enthusiasts, or growers interested in harvesting the nuts. But for homeowners willing to take a risk, it can make a surprisingly good landscape tree under the right conditions. Butternut will be most likely to survive the fungal canker disease that has ravaged the species when isolated in a landscape setting far from natural stands of butternut. Make sure to regularly inspect the tree and prune away any suspicious branches as soon as you spot them. But if you can avoid butternut canker, this can be a fairly easy tree to grow if it gets adequate sun and moisture.
Light
Butternut trees need full sun and are intolerant of shady conditions. These are best grown in open spaces far from other trees and plants.
Soil
In the wild, butternut is usually found growing in the moist soil of bottomlands around streams, and it will do best in rich soils that are fairly moist and slightly acidic.
Water
This tree does best with fairly consistent moisture—at least 1 inch per week through rainfall and/or irrigation. Make sure to water it during dry spells.
Temperature and Humidity
Butternut trees can thrive in the temperatures found throughout its hardiness range, zones 3 to 7, but it has been known to survive in zone 8 as far south as Georgia. It does equally well in humid and dry air conditions, provided it gets adequate soil moisture.
Fertilizer
Feed this tree only if a soil test determines there is a deficit of some essential nutrient. Good soils generally do not require fertilizing in order to grow butternut trees.
Butternut Varieties
There are no named cultivars of the J. cinera, but a hybrid cross between the butternut and Japanese walnut, Juglans ailantifolia, seems to possess some of the Japanese walnut’s resistance to canker disease. Both the hybrid and J. ailantifolia itself are good substitutes for butternut in areas that are susceptible to butternut canker.
Pruning
The most effective pruning will occur while a butternut tree is still young. Thin, weak branches should be pruned away to open up the center of the tree to light and air. Prune to eliminate sharp V-shaped crotches, keeping those with a U shape. Keep the crown raised above the ground by pruning away downward-facing branches from the lower limbs. Without such pruning, the tree’s crown may grow too low to walk beneath. Don’t remove more than one-fourth of the tree’s crown material at any one time, as this can make the tree susceptible to disease. Pruning near the end of the dormant season (late winter) is the best time to perform major pruning. If cankers appear on any branches, prune them immediately down to about 8 inches below the affected areas; this may prevent the disease from spreading and killing the entire tree.
Propagating Butternut Trees
The butternut is monoecious, which means that it grows separate male and female flowers during its bloom in the spring. These flowers are fairly small—only a few inches long—and generally insignificant. Its male flowers are a light yellow-green, while its female flowers are lighter yellow and yield the tree’s namesake edible nuts in the fall. The butternut grows yellow-green fruit during its bloom that contains nuts encased in husks. These nuts mature throughout the summer and are generally completely mature by the fall. When the husks are cracked, they yield a meaty, edible nut. Butternuts are relatively easy to propagate by planting the ripened nuts collected from a mature tree in fall. As the nuts begin to fall from the tree, gather a few up. Boil the nuts to loosen the outer husks, then crack open and remove the outer layer. Plant the nuts in fall, about 2 inches deep, in the chosen location. Butternuts need a period of cold stratification to germinate, so fall is the best time for planting. Cover the area with a thick layer of mulch. The seed should sprout into a sapling the following spring. As it is becoming established, protect the sapling with a cage of wire mesh to prevent animals from gnawing on the stem.
Common Pests and Diseases
Butternuts are susceptible to multiple insects, including bark beetles, caterpillars, borers, and lace bugs. The grackle also can do damage to butternuts—they eat its fruit. Butternut canker, a disease spread by fungus, has wreaked havoc on the native butternut population to the point that in some areas it has been completely eradicated. There is no cure and trees stricken with the canker generally die within a few years. Early signs of the canker are dead branches and stems, particularly in the tree’s crown; from these branches, the canker spreads to the lower foliage. Though the canker continues to spread the continent, many healthy butternuts still exist— free-standing trees apart from forests seem less susceptible. This means that isolated trees in the landscape have a decent chance of survival.
