Black walnuts trees are valuable for the nuts and dark timber. While the black walnut tree may take up to 35 years to reach maturity for timber harvest, the tree's fruits, or nutmeats, are utilized in the food industry. The return on investment for planting black walnuts is two-fold, first for the nutmeats and later as valuable timber. Perhaps the most economical method of propagation for black walnuts is planting the large nutmeat seed directly into the soil.
Wear gloves and old clothes, as the black walnut hulls will cause dark stains. Collect the walnuts as soon as the nuts hit the ground. Fill a plastic bucket with the green husk walnuts that have as few defects as possible.
Soak the walnuts in water for two hours to aid in removing the outer husks.
Peel the outer husks from the nuts. Place the peeled nuts back into the plastic bucket. Fill the bucket with water. Remove all floating nuts.
Remove the remaining nuts from the plastic bucket. Spread the nuts on a flat tabletop, away from any predator access. Allow the nuts to dry.
Place the nuts in a plastic bag. Set the nuts in a refrigerator or a cold storage that will maintain temperatures between 34 to 41 degrees F for a 90- to 120-day stratification period.
Plant the seeds the next spring. Prepare the planting field after the nuts are placed in stratification. Plant the seeds in a grid formation 15 feet apart. Mow the field to remove all errant weeds and shrubs.
Make a hole using a shovel or by inserting a rock bar 2 inches into the soil. Place two black walnut seeds into one planting location, approximately 3 inches apart. Cover the seed with the native soil.
Pound a single wooden stake into the ground to identify the seed planting holes. The black walnut seeds should germinate in four to five weeks. Keep the field mowed.