English walnut
Also known as
Persian walnut, Common walnut
Keep this plant’s care guide close at hand.
Get the appAbout English walnut
Juglans regia, commonly called English or Persian walnut, is a large, long-lived deciduous tree prized for its nutritious nuts and fine timber. Mature trees often reach 15–25 m with a broad, rounded crown and a deep root system with strong lateral spread. Leaves are pinnate with 5–9 leathery leaflets that release a resinous scent when crushed. The species is monoecious: drooping male catkins and small terminal female flowers appear in spring; fruits are green, fleshy drupes enclosing the familiar corrugated shell and edible kernel. It thrives in deep, fertile, well-drained loams with adequate moisture and full sun, and it tolerates mildly calcareous soils. Walnuts produce juglone, an allelopathic compound that can inhibit sensitive plants. Good nut production requires sufficient winter chilling and a long, warm, frost-free period for kernel fill. The tree is adapted to temperate climates (USDA zones 5–9) but flowers are frost-sensitive. Common challenges include walnut blight, scale insects, codling moth, and sunscald on young bark. Proper siting, pruning, irrigation, and cultivar choice greatly improve health and yield.
Taxonomy
Properties & Requirements
How to care for English walnut
Water
Keep soil evenly moist, never waterlogged. For the first 3–5 years, give a slow, deep soak every 7–10 days during dry weather, wetting the root zone just beyond the drip line. Use drip lines or soaker hoses to deliver water gradually and reduce leaf wetness. Mature trees need fewer but deeper irrigations, especially during kernel fill in mid to late summer. Mulch 5–8 cm deep to conserve moisture. Reduce watering in autumn to help harden wood before winter, and avoid standing water at any time.
Light
Requires full sun for best growth and nut production—at least 6–8 hours of direct light daily. Light shade reduces flowering and kernel quality. Site the tree with ample lateral space to prevent competition and ensure uniform light penetration into the canopy. Maintain an open structure through selective pruning to improve internal light and airflow, which helps limit disease pressure. Avoid north-facing frost pockets where spring sun arrives late yet cold air accumulates, increasing bloom damage risk.
Nutrients
Test soil before fertilizing. Young trees benefit from modest nitrogen in early spring to drive canopy establishment; use a balanced, slow-release formulation (e.g., 8-8-8 or 10-10-10) and keep fertilizer outside the trunk’s immediate base. Incorporate compost and maintain a mulch ring to recycle nutrients and conserve moisture. Avoid heavy late-summer nitrogen that can spur tender growth and increase frost risk. Monitor micronutrients—especially zinc and boron—for nut set and kernel fill; address deficiencies with targeted foliar or soil applications based on leaf analysis.
Temperature
Hardy in USDA zones 5–9. Dormant trees tolerate roughly −20 to −10 °F (−29 to −23 °C), but emerging shoots and flowers are damaged by late frosts near 28 °F (−2 °C). Optimal growing-season temperatures are about 65–86 °F (18–30 °C). Prolonged extreme heat above ~100 °F (38 °C) can reduce nut quality and increase sunburn; provide soil moisture and consider trunk/limb protection. Requires moderate winter chilling for reliable budbreak; avoid frost pockets and sites with strong, desiccating winds.
