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Black walnut trees are easy to start from seed. In a favorable site, they often reach 80 to 100 feet in height and their crowns may spread an equal distance.
Choose the planting site carefully
Black walnuts secrete juglone, a chemical that is toxic to many plants. Locate your planting at least 60 feet from any sensitive plants or garden areas.
Black walnut trees will do very well in a moist bottom area that is well drained, or on a moist hillside or upland site. They will tolerate occasional dry spells, and they accept any soil pH from moderately acidic to moderately alkaline.
If you are planting walnuts as garden trees, space the plantings about 60-70 feet apart so their crowns can develop a majestic spread as they mature. However, if you're planting black walnuts for their valuable wood, plant them about 30 feet apart so their trunks will grow long and straight.
Planting the seeds
Gather the nuts as they fall from a tree in your area, and remove the husks. Place half a dozen nuts several inches apart in a cluster, four or five inches deep. If you have squirrels, lay a piece of hardware cloth over the planting spot and pin it to the ground with v-shaped wires. Lay a mulch of straw or leaves over the hardware cloth to reduce the freeze/thaw cycles. Mark the site so you can find it again.
After fall planting and a session of damp, cold weather, the walnut seeds will germinate in the spring. Remove the mulch and hardware cloth from the planting spot in late winter, and mark the spot clearly so you don't accidentally mow over it! After the baby trees have grown for a few months, choose the best one and eliminate the others.