GROWING A WALNUT TREE
A walnut is the edible nut of the walnut fruit, produced by the walnut tree (Juglans regia). Walnut trees are native to the mountains of Central Asia, but are grown worldwide and have been cultivated by humans for thousands of years. There are several varieties of walnut, so it is important to choose one that is right for your area.
Grafted walnut trees and walnut seedlings are all similar sizes that can grow to approximately 40’ tall and need 35’ spacing.
Walnuts are self-fertile and require no pollinator. While walnuts are self-fertile, generally a pollination partner will increase the size and quality of the harvest.
Pollination is important during your orchard planning as well, since walnuts are wind pollinated they should be planted no further than 200 feet apart, to ensure proper cross-pollination.
USDA HARDINESS ZONE
Walnut trees are hardy to USDA zones 4-9, unless otherwise noted. This rating tells you the minimum winter temperature the plants typically survive when properly hardened off. On our web site you will find a USDA Hardiness Maps which provides information on the average minimum winter temperature in your location, by zip code.
Many plants native to locations that have cold winters have a Chill Hour requirement to ensure uniform waking up of flower and leaf buds in the spring. The chill hour requirement of plants varies by species, by cultivar, and sometimes by the level of dormancy achieved.
WHERE TO PLANT YOUR TREE
Walnut trees need to be planted where they receive at least 8 hours of direct sunlight measured in early summer (late June to early August). Sufficient sun exposure triggers the initiation of new flower buds for the next growing season, without which there will be no fruit. Fruit ripening and flavor development are also benefited by the carbohydrate production stimulated by the sun, as well as it’s heat.
Walnuts tolerate a wide variety of soils so long as they are well drained and moderately rich with a pH around 6.3-6.8. Improve your soil where you intend to plant by mixing an inch or two of plant based organic matter (manures are best for vegetable gardens), peat, or coconut coir into an area 1 1/2 to 2 times the diameter of the needed planting hole and up to a foot deep. A 2-4” deep layer of mulch (straw, leaves, or wood chips) applied after planting will continue to improve the soil.
Allow sufficient space for both the top of the tree and it’s roots when selecting the planting location. Refer to size descriptions for each variety, keeping in mind these are generally managed or pruned sizes, not maximum potential sizes. If you are planting an orchard be sure to include enough space between rows for transporting supplies in and fruit out.