Black walnut and butternut roots excrete an acid (juglone) that inhibits the growth of many plants, so plant far away from vegetables and flowers. Weed control is vital to the initial years of walnut tree growth. All walnuts benefit from mulching. Walnut trees grown for nut crops require large crowns; those grown for veneers need a straight trunk. To grow for both, veneer requirements prevail, so prune for straight growth.
Carpathian walnuts grow rapidly, about 4-5 feet per year. Black walnuts, the largest Juglans, bear nuts that are high in protein and polyunsaturated oils and should be used sparingly in cooking. Grafted trees usually yield 3-4 times higher kernel filling than seedlings. Butternuts, or white walnuts, are the hardiest Juglans, don't require as much water, and also have a rich buttery taste. Buy as a small tree as possible to minimize injury to the taproot which, in Juglans, is very straight and long. True nut flavor and quality may not emerge for 2-3 years after bearing, so don't judge trees prematurely.
Height - 20-80 ft.
Due to the indelible stains imparted by the husks, always wear gloves. Remove the outer husks within 1 week of harvest; let dry for several days, after which the husks will be easy to remove. There are 2 methods to de-husk the nut.
- Use a corn sheller equipped with a flywheel and pulley, driven by 1/4 hp motor.
- Take them to a professional huller.
Rinse off hulled nutshells and place in water. Remove the rotten and diseased nuts that float to the top. Dry and cure by spreading in one layer in a cool, dry, well-ventilated area. They're ready for storage when the kernels rattle in the shell, 1-2 weeks, or when unshelled kernels snap when bent. Store shelled nuts in plastic bags with holes, or in tightly sealed tin cans lined with paper (with a hole punctured in the side of the can beneath the lid), or freeze. Store unshelled nuts in an unheated shed over the winter; in spring move them to a cool place. Fresh walnuts can be stored at 32°-36°F for 1 year.
Breadth - 20-40 ft.
Spacing - 10 ft. When 10 ft in diameter (about 25 years), thin to 22-50 ft.
Root Depth - Very deep
pH - 5.5-7.0
Bearing Age - 3-5 years for nuts; 10-20 years to produce veneer for market.
Pollination - All need cross-pollination.
Chilling Requirements - All walnuts require some chilling hours.
Site - Full sun; deep, well-drained loam. Don't plant anywhere near vegetable garden or orchard.
Water - Medium
Fertilizer - don't fertilize the first year. In following years, apply compost or well-rotted manure.
Training - Free-standing tree: central leader.
Walnut caterpillar Datana integerrima
Credit: Lacy L. Hyche, Auburn University, Bugwood.org
Height - 20-80 ft.
Pruning - Unlike most fruit and nut trees, prune in the fall. Don't start until 4-5 years old. Cut out dead or diseased wood, and crossed or competing branches.
Walnut Pests & Diseases
Aphids, blue jay, codling moth, fall webworm, mouse, navel orangeworm, squirrel, walnut caterpillar, walnut husk fly, walnut maggot.
Crown gall, walnut anthracnose, walnut blight, walnut bunch.