Walnut
Juglans regia
Late summer is the only safe pruning window — and the squirrels reach the fallen nuts first.
- Type
- Fruit · Perennial
- Botanical family
- Mixed / other
- Foliage color
- Green · Gold and chartreuse
- Sunlight
- Full sun, if the nut crop is the point.
- Watering
- Water while young; an established tree rarely asks for it.
- Feeding
- A compost mulch in spring; extra feeding is seldom needed.
- Frost tolerant
- Yes
- Flowering
- May
- Pruning
- Prune in late summer and at no other time — and not much then.
- Mar–May Bud Break
- May–May Flowering
- May–Aug Fruit Set
- Aug–Oct Harvest
- Oct–Dec Leaf Fall
- Jan–Mar Leaf Fall
- Plant spacing
- 27 ft 5 in
- In-row spacing
- 27 ft 5 in
- Between rows
- 34 ft 5 in
- Square-foot density
- Not suited to SFG
- Root system
- Woody, with a taproot it keeps
- Working depth
- 24 in–5 ft
- Can reach
- 10 ft down where the soil allows
- Spread
- 49–82 ft across, about 1.5–2.5× the width of the plant
It anchors downwards as well as sideways, which is what lets it stand in a gale and what makes it hate being moved. Plant it small: past a few years in the ground a taprooted tree transplants badly, and often not at all.
The roots release juglone, which poisons a long list of neighbours: tomatoes, potatoes, apples, blueberries, rhododendrons and birch among them. The affected ground is the root spread rather than the shade, so it reaches well beyond the canopy, and it persists for years after the tree is felled.
The habit is Walnut’s own; the figures are what that habit usually comes to at this size, not a measurement of this species. Roots follow the soil either way: a compacted pan, a high water table or heavy clay stops them well short of any of it, and deep open ground lets them go further.
- Codling moth Its caterpillars tunnel to the core of apples and pears, leaving frass-filled exit holes. Hang pheromone traps from late spring and pick up windfalls promptly.
- Squirrels Dig up newly planted bulbs and raid fruit and nuts. Lay wire mesh over pots and freshly planted bulb beds until shoots emerge.
- Blight Walnut blight
- Leaf spot Walnut leaf blotch
Beneficial predators that hunt this plant's pests — grow their favourite flowers nearby to recruit them. companion plant
- Bats ChiropteraHunts Codling moth
A single bat takes hundreds of moths and mosquitoes in a night, and the moths are the parents of your cutworms, corn earworms and hornworms. Put up a bat box on a warm south wall, leave a night-scented corner unlit, and never spray after dark.
- Parasitic wasps Braconidae & TrichogrammaHunts Codling moth
Tiny, stingless wasps that lay eggs in or on caterpillars, aphids, and moth eggs — the white cocoons riding a hornworm are their calling card, so leave that caterpillar be. Umbel flowers with shallow nectar keep the adults fuelled.
Comfrey, Clover
The Cottage Garden Companion — the gardener's herbarium at cottagegardencompanion.com