How to grow walnut
Overview
Walnut (Juglans regia) is a large deciduous tree grown for its nutrient-dense nuts and strong landscape presence. It is a long-term investment that improves with age, requiring deep, well-drained soil and ample space. Key to success is planting in a sheltered, frost-free site with full sun and avoiding waterlogged roots.
Varieties
- Chandler — A popular, high-yielding variety with thin shells and good kernel quality, suited to temperate and cool zones.
- Franquette — Late-blooming, frost-resistant variety ideal for cooler climates; produces large, flavourful nuts.
- Wilson's Wonder — An Australian-bred variety with excellent flavour and reliable cropping in temperate regions.
Soil Preparation
Walnut prefers deep, fertile, well-drained loam with a pH of 6.0–7.0. Avoid heavy clay or waterlogged soils. Before planting, incorporate well-rotted compost or aged manure into the top 30 cm of soil. Improve drainage with raised beds if necessary.
Growing Guide
Plant walnut in deep, well-drained soil with a pH of 6.0–7.0 in a position that receives full sun. Space trees at least 10–12 m apart to accommodate their mature canopy. Dig a hole twice the width of the root ball, backfill with native soil, and water in well. Stake the tree for the first two years to establish a strong central leader. Mulch deeply with organic matter, keeping it away from the trunk to prevent collar rot.
Sowing
Sow walnut seeds directly in autumn (April–May) at 5–8 cm depth, spaced 10–15 cm apart in a nursery bed. Germination takes 3–6 months after a cold period. Transplant seedlings to their final position in winter when dormant. Alternatively, plant grafted trees from a nursery for faster cropping.
Care
Feed walnut with a balanced fertiliser (e.g., 10-10-10) in early spring and again in late summer at 1–2 kg per mature tree. Prune in winter dormancy to establish a strong central leader and remove crossing or dead branches. Mulch deeply with wood chips or straw to retain moisture and suppress weeds, but keep mulch off the trunk.
Companion Planting
Avoid planting sensitive plants like tomatoes, potatoes, and peppers near walnut due to juglone toxicity. Good companions include comfrey, dandelion, and clover as ground cover under the canopy. Keep a 3–4 m clear zone around the trunk for young trees.
Common Pests & Risks
Codling moth can tunnel into developing nuts; use pheromone traps and spray with spinosad in early spring. Walnut blight (bacterial canker) causes dark lesions on shoots and nuts; prune out infected wood and apply copper sprays in autumn. Borers may attack stressed trees; maintain tree health and avoid wounding the trunk.
Harvesting
Harvest walnuts when the hulls split open and the nuts drop naturally to the ground, typically from late summer to autumn. Gather promptly to avoid mould and pest damage. Remove the outer husk and dry the nuts in a single layer in a warm, airy spot for 2–3 weeks before storing.
In the Kitchen
Harvested walnuts can be eaten fresh or dried for storage. Use in baking, salads, or as a snack. Store in a cool, dark place for up to 6 months. The green hulls can be used to make a natural dye or tincture.
Troubleshooting
Yellow leaves: often due to waterlogging or poor drainage; improve soil aeration. Brown leaf edges: may indicate salt burn from fertiliser; reduce application rate. Black spots on nuts: walnut blight; prune infected wood and apply copper spray. Poor nut set: lack of pollination; plant two different varieties for cross-pollination. Stunted growth: juglone toxicity from nearby walnuts; avoid planting sensitive species within 10 m.