Walnut care guide: when & how to prune, fertilize and spray
Juglans regia (English/Persian) / J. nigra (black walnut) · USDA zones 5–9
Large, handsome trees. English (Persian) walnuts have thin shells; Carpathian strains are hardy to zone 5. Black walnut has rich-flavored, very hard nuts. Walnut roots release juglone, which stunts tomatoes, potatoes, peppers, blueberries, azaleas and many other plants, so site them away from vegetable gardens. Walnuts bleed heavily if pruned in late winter or spring. Prune in summer or early winter instead.
☀️ Sun
Full sun.
💧 Water
Deep watering in dry spells, especially while nuts fill in midsummer.
🪱 Soil
pH 6.0–7.5. Deep, fertile, well-drained loam. Compost at planting. Keep juglone-sensitive plants out of the root zone (about 1.5× the canopy width).
How and when to prune walnut
Prune in summer (not late winter)
When: 12–16 weeks after the last spring frost.
- zones 3–5: about Aug 2–30
- zones 6–7: about Jul 8 – Aug 5
- zones 8–10: about May 20 – Jun 17
Walnuts bleed heavily if cut in late winter or spring. Summer cuts seal quickly.
- Young trees: train to a central leader with well-spaced scaffold branches.
- Remove dead, broken, crossing and low branches.
- Hire an arborist for large limbs on mature trees.
Tools: Loppers, Pruning saw, Pole saw
Fertilizing walnut
Spring feeding
When: from 2 weeks before to 2 weeks after the last spring frost.
- zones 3–5: about Apr 26 – May 24
- zones 6–7: about Apr 1–29
- zones 8–10: about Feb 11 – Mar 11
Walnuts need steady nitrogen for strong growth and nut fill.
- Broadcast fertilizer under and beyond the canopy and water it in. Mature trees on good soil may need only compost.
What to use: 🌿 Organic tree & shrub food (e.g. Espoma Tree-tone 6-3-2) · 🌿 Finished compost or composted manure · Fruit tree spikes or 10-10-10 granular
Spraying & disease prevention for walnut
Walnut blight protection
When: from the last spring frost to 2 weeks after, then every 1 weeks (3 times a season).
- zones 3–5: about May 10–24
- zones 6–7: about Apr 15–29
- zones 8–10: about Feb 25 – Mar 11
The bacteria infect catkins and young nutlets during wet weather at bloom.
- In wet springs, spray copper at early bloom (when catkins and tiny female flowers appear), then twice more at 7–10 day intervals.
What to use: 🌿 Copper fungicide (e.g. Bonide Captain Jack's Liquid Copper)
Husk fly protection (if needed)
When: 12–14 weeks before the first fall frost, then every 2 weeks (3 times a season).
- zones 3–5: about Jun 25 – Jul 9
- zones 6–7: about Jul 19 – Aug 2
- zones 8–10: about Aug 25 – Sep 8
Husk fly lays eggs in husks in midsummer, staining shells and making them hard to clean.
- If you had husk fly last year, coat reachable nuts with kaolin clay, or use a spinosad bait spray as the label directs.
What to use: 🌿 Kaolin clay (e.g. Surround WP) · 🌿 Spinosad (e.g. Captain Jack's Deadbug Brew)
Soil, compost & mulch for walnut
Refresh mulch
When: 2–6 weeks after the last spring frost.
- zones 3–5: about May 24 – Jun 21
- zones 6–7: about Apr 29 – May 27
- zones 8–10: about Mar 11 – Apr 8
Mulch keeps roots cool and moist, suppresses weeds and slowly feeds the soil. Applying it after the soil warms lets roots wake up first.
- Spread 2–3 in (5–7 cm) of mulch over the root zone.
- Keep mulch 2–3 in (5–7 cm) away from stems and trunks. Mulch piled against bark invites rot and rodents.
- Don't go deeper than 3 in (7 cm) in total. Too much mulch suffocates roots.
What to use: 🌿 Shredded hardwood or pine bark mulch
Other care for walnut
Harvest walnuts
When: from 6 weeks before the first fall frost until the first fall frost.
- zones 3–5: about Aug 20 – Oct 1
- zones 6–7: about Sep 13 – Oct 25
- zones 8–10: about Oct 20 – Dec 1
Walnuts are ready when the green hulls begin to split and nuts start to fall.
- Gather nuts every few days as they fall. Shake limbs to bring down the rest.
- Remove hulls promptly (wear gloves; black walnut hulls stain hands for weeks), then rinse the nuts.
- Dry nuts in a single layer in a warm, airy, shaded spot (or mesh bags hung indoors) for 1–3 weeks until the kernels snap rather than bend.
- Store dried nuts in the shell in a cool, dry place, or shelled in the fridge or freezer. Shelled nuts go rancid at room temperature.
Tools: Gloves, Buckets
Common walnut problems and how to fix them
Walnut blight
Signs: Black spots on leaves, catkins and young nuts in wet springs; nuts drop or blacken.
What to do: Copper sprays at early bloom and again 7–10 days later in wet weather.
Walnut husk fly
Signs: Husks turn black, soft and slimy; stained shells.
What to do: Harvest promptly and clean nuts. Kaolin clay or spinosad bait sprays in midsummer.
Codling moth
Signs: Worm tunnels into nuts.
What to do: Pick up dropped nuts. Pheromone traps help time sprays of spinosad if needed.
Juglone damage nearby
Signs: Tomatoes or shrubs near the tree wilt and die.
What to do: Move sensitive plants away and grow juglone-tolerant plants near walnuts.
Walnut care FAQ
When should I prune walnut?
Prune in summer (not late winter): 12–16 weeks after the last spring frost (around Jul 8 – Aug 5 in zones 6–7). Large, handsome trees. English (Persian) walnuts have thin shells; Carpathian strains are hardy to zone 5. Black walnut has rich-flavored, very hard nuts. Walnut roots release juglone, which stunts tomatoes, potatoes, peppers, blueberries, azaleas and many other plants, so site them away from vegetable gardens. Walnuts bleed heavily if pruned in late winter or spring. Prune in summer or early winter instead.
What is the best fertilizer for walnut?
Walnuts need steady nitrogen for strong growth and nut fill. Good options: Organic tree & shrub food (e.g. Espoma Tree-tone 6-3-2); Fruit tree spikes or 10-10-10 granular; Finished compost or composted manure.
What should I spray on walnut?
Walnut blight protection (from the last spring frost to 2 weeks after); Husk fly protection (if needed) (12–14 weeks before the first fall frost). Products: Copper fungicide (e.g. Bonide Captain Jack's Liquid Copper); Kaolin clay (e.g. Surround WP); Spinosad (e.g. Captain Jack's Deadbug Brew). Always follow the label.
What soil does walnut need?
Deep, fertile, well-drained loam. Preferred pH 6.0–7.5. Compost at planting. Keep juglone-sensitive plants out of the root zone (about 1.5× the canopy width).
How much sun and water does walnut need?
Sun: Full sun. Water: Deep watering in dry spells, especially while nuts fill in midsummer.
What are common walnut problems?
Walnut blight: Black spots on leaves, catkins and young nuts in wet springs; nuts drop or blacken. Copper sprays at early bloom and again 7–10 days later in wet weather. Walnut husk fly: Husks turn black, soft and slimy; stained shells. Harvest promptly and clean nuts. Kaolin clay or spinosad bait sprays in midsummer. Codling moth: Worm tunnels into nuts. Pick up dropped nuts. Pheromone traps help time sprays of spinosad if needed. Juglone damage nearby: Tomatoes or shrubs near the tree wilt and die. Move sensitive plants away and grow juglone-tolerant plants near walnuts.
More nut trees care guides
Timings are given relative to your average frost dates, with examples for typical US climates. Always read and follow product labels.