How to Grow Walnut Trees

Planting and site

Choose a deep, fertile, well-drained spot in full sun with room for a large canopy. Walnuts develop a strong taproot, so start them where they will grow or transplant young.

1. 1Collect and clean — Gather fallen nuts in early autumn when ripe and remove the husks.
2. 2Cold-stratify — Provide about 90 to 120 days of cold, moist chilling; fall outdoor planting supplies this naturally.
3. 3Plant shallow — Set nuts only a couple of inches deep, just below grade, in loose fertile soil.
4. 4Water in the first year — Keep soil consistently moist through the establishment year to build a strong root system.

Juglone and companion planting

Juglone (5-hydroxy-1,4-naphthoquinone) is a respiration inhibitor concentrated in walnut buds, nut hulls and roots. Toxic effects of a mature black walnut can reach roughly 50 to 80 feet from the trunk, strongest within the dripline. Sensitive plants show yellowing, wilting leaves, especially in hot, dry weather.

• Keep tomatoes, peppers, eggplant, potatoes, blueberry, rhododendron, mountain laurel and peony away from the root zone.
• Many plants are juglone-tolerant and grow fine nearby; check an Extension tolerance list before planting.
• Lined raised beds and good drainage with added organic matter reduce root contact and speed juglone breakdown.

⚠ Do not compost black walnut leaves, hulls or wood chips into vegetable beds; juglone can persist and injure sensitive crops.

Sources

Reviewed 2026-07-18. We cite university Extension, government, and established horticultural sources — and never invent pesticide rates or dangerous treatments.

• University of Maryland Extension — Walnut Toxicity (Juglone) — Juglone from black walnut roots inhibits sensitive plants; toxic zone extends about 50-80 feet, strongest at the dripline; lists susceptible species.
• WSU Extension — Do Black Walnut Trees Have Allelopathic Effects on Other Plants? — Confirms juglone allelopathy and identifies tolerant versus susceptible garden plants.
• University of Missouri Extension — Growing Black Walnut (Agroforestry) — Walnuts need deep, well-drained fertile soil; nuts require cold stratification to germinate.

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