Black Walnut Juglans nigra

Black walnut is an edible, deciduous tree in the walnut family (Juglandaceae) and is native to a broad swath of central and eastern North America. It grows well on rich bottom lands, in moist, fertile coves and on lower slopes throughout North Carolina. The species epithet is Latin for "black" in reference to the dark bark and stain of the tree and the nuts.

Black walnut prefers moist, organically rich, well-drained soils. It prefers full sun and will tolerate partial shade. However, it is intolerant of full shade. It grows in wet to dry loam, clay or sandy highly acidic to slightly alkaline soil. Its survival, growth and quality in less fertile sites is problematic.This species is particularly resistant to heat, drought and soil compaction. The tree's leaves, stems and roots contain juglone, which inhibits the growth of some plants beneath the tree's dripline. Plants known to be sensitive to juglone include azaleas, peonies and some fruits and vegetables, such as tomatoes, apples and blueberries. Propagate by seed. It has a very deep taproot, making it difficult to transplant.  

This massive tree can grow to 50 to 90 feet high with a 3 to 6 foot diameter trunk when mature. It has the habit of losing its lower branches to begin its spread at 20 feet above the ground. Each tree bears both male and female flowers (monoecious). In October the trees develop brown to black nuts inside a yellow-green husk that heavily stains skin and clothing. Nut production can sometimes begin as early as 6 years but usually takes 20 years for a substantial crop. The nuts are edible but difficult to remove from the husk, and the fleshy husk can be used to make a brown dye. Once used by Native Americans medicinally, the tree is a scarce, valuable native hardwood used for furniture and veneer. It is a host plant for the larvae of the hickory horndevil (Citheronia regalis) moth, banded hairstreak butterflies and the luna moth. Squirrels eat the nuts.

The black walnut works well as a shade tree in meadow and woodland locations. It also can be used in butterfly, edible, native and nighttime gardens.

Diseases, Insects and Other Plant Problems: Under pressure in some areas from thousand cankers disease. Other potential diseases include anthracnose, bacterial blight, root rot, canker, leaf spot and shoot dieback. Watch for aphids, fall webworm and a variety of foliage chewing caterpillars.

VIDEO Created by Laura Barth for "Vegetables, Herbs, Fruits, and Nuts," a plant identification course developed in partnership with Longwood Gardens.