How to grow Walnut

Where to plant

Walnuts need full sun and deep, fertile, well-drained soil, and space for a large, long-lived tree. Plant them well away from houses, vegetable gardens and other trees.

Black walnut produces juglone, a natural compound in its roots, buds, leaves and hulls that stunts or kills many sensitive plants. Its effect can extend 50 to 80 feet from the trunk and is strongest within the drip line. Tomatoes, potatoes, eggplant and peppers, apples, blueberries, lilacs, peonies, rhododendrons and azaleas are particularly sensitive. Other walnuts produce less, but it is wise to keep vegetable beds away from any walnut.

• Northern California and the Central Valley: English walnut's home ground. Plant bare-root trees in winter and give them plenty of room.
• Southern California: walnuts need roughly 500 to 1,000 hours of winter chill, so they crop in inland valleys, not on the coast. Ask for a lower-chill variety.
• Pacific Northwest: English walnut suits the milder valleys. Plant in late winter or fall.
• Northeast, Midwest, Mid-Atlantic and Mountain West: choose Carpathian English walnut or black walnut. Plant as soon as the ground can be worked, or in fall.
• Mid-South and Southern Plains: black walnut does well and is native; English walnut struggles with humid summers.
• Northern Plains: black walnut only, in the milder zone 4 areas.
• Texas, the Gulf South and North Florida: English walnut lacks chill and suffers in the humidity. Native black walnut grows on deep, good soil; pecan is the easier nut tree.
• Central and South Florida, the low desert, Hawaii and Alaska: not suited.

Choosing a variety

• English walnut (Juglans regia) gives thin-shelled nuts; choose varieties suited to your chill hours and season. Carpathian strains are the hardiest for cold regions.
• Black walnut (Juglans nigra) is native to the eastern and central US, very hardy and drought tough, with hard shells and rich flavor. Grafted named varieties crack more easily than wild seedlings.
• Walnuts are wind pollinated and largely self-pollinating, but a second tree or variety nearby often improves crops.

How to plant

1. Plant bare-root trees while dormant, in winter in mild areas or as soon as the ground can be worked in cold areas.
2. Dig a wide hole and spread the long taproot down without bending it, setting the tree at the depth it grew in the nursery.
3. Water in thoroughly and mulch a wide circle, keeping the mulch off the trunk.
4. Protect young trunks from sunburn in hot inland areas with white trunk paint.

Watering and feeding

Water young trees deeply through their first few summers. In dry-summer climates such as California, mature English walnuts still need deep irrigation through the summer for good nuts, but overwatering and poorly drained soil cause root and crown rots.

Feed young trees lightly in spring; established trees in good soil need little.

Harvesting

Walnuts ripen in fall. English walnuts are ready when the green hulls split and the nuts drop; shake or knock them from the tree and gather them promptly. Black walnuts fall in their thick green hulls, which blacken and stain hands, so wear gloves.

Remove the hulls, wash the nuts, and dry them in shallow layers in a warm, airy, shaded place for a few weeks until the kernels are crisp. Store in the shell in a cool, dry place, or freeze shelled kernels.

Using it

Use walnuts in baking, salads and sauces, or eat them toasted. Black walnut has a stronger, distinctive flavor prized in ice cream and cakes.