Tree · Juglandaceae
Walnut
Juglans regia
Give it deep soil, full sun, and room to spread, and a walnut takes off, shading the yard for generations and filling baskets each fall.
Full sun
Every 7–21 days
USDA 5–9
39–59 ft · 12–18 m
Overview
A walnut is a long-lived shade tree that pulls its weight twice over, once for the nuts and once for the sheer presence it brings a yard. It belongs to the walnut family, climbs to 60 feet (18 m), and throws out a wide, open crown, so hand it a space all its own. Feed it deep, fertile soil and full sun and it will crop and shade for generations.
Reach for the English or Persian walnut when kernels are the goal, or the native black walnut when you want hard-shelled nuts and dark, sought-after timber. Both trees pump out a compound called juglone from their roots and hulls that keeps a few sensitive plants in check nearby. Work with that quirk and you will nail the tree's spot and pick smart companions for the ground below.
A walnut rewards the grower who plays the long game. A grafted tree needs a few years to hit its stride, and the tumbling nuts with their staining hulls will splatter any paving beneath, so set it well clear of the house and walks. Get the spot right and you cash in on years of shade and a crop that rolls in every fall.
Care
The short version: load it up with full sun and deep, well-drained loam, soak it deeply while it is young, then just top it up now and then once it settles. Feed in early spring, prune in late summer to skip the sap bleed, and hand it plenty of room to run.
Light
Walnuts chase full sun to crop hard, and they will settle for only light partial shade. Box one in with buildings or bigger trees and it grows lopsided and drops its yield, so throw open the sky on every side and let it rip.
Water
Soak young trees deeply every 1 to 3 weeks through those first few seasons and the roots dig right in. An established walnut laughs off dry weather, but slip it a deep drink now and then across a dry summer and it pushes out its heaviest crop.
Soil
Set a walnut into deep, fertile, well-drained loam and it thrives. Keep the pH between 6.0 to 7.5, and dodge waterlogged or shallow ground at all costs, since wet feet is the one thing that stops a walnut cold.
Temperature
A walnut shrugs off a huge range, from about -22°F to 95°F (-30°C to 35°C), so cold rarely fazes it. The catch is a late spring frost that can nip the young growth and catkins, which is exactly why later-leafing cultivars pull ahead in cold country.
Humidity
Everyday outdoor humidity of 40% to 70% suits a walnut just fine, so skip the fuss. Damp, still air in a wet spring, though, fuels blight, so an open canopy that dries fast beats any gauge reading hands down.
Feeding
Feed in early spring before the growth flush with a nitrogen-focused balanced fertilizer, steered by a soil or leaf test. Walnuts burn through nitrogen, but test before you feed, since anything extra just washes straight away.
Pruning
Steer a young tree to a single central leader, then clear out the dead, crossing, and low limbs as it powers up. Time every cut for late summer or early fall, because a walnut bleeds sap heavily from wounds made in late winter and spring.
Repotting
A walnut is built for the landscape and orchard, not a pot, so once it hits the ground repotting is off the table. Leave a young one too long in a nursery pot, though, and you will spot roots circling the pot and stalled top growth, your cue to get it planted.
Size & spacing
Brace for a big tree, 40 to 60 feet (12 to 18 m) tall with a spread of 33 to 49 feet (10 to 15 m). Set it well clear of buildings, walks, and other trees so the crown can stretch out and the staining nuts stay off the paving.
When to plant
A walnut moves with the seasons, so get it in the ground while it is still dormant. Plant bare-root or balled trees in late winter to early spring, watch the wind-pollinated catkins swing out in spring, and pull the ripe nuts in fall as the hulls crack open.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Plant: Plant bare-root or balled-and-burlapped trees during dormancy, late winter to early spring
- Harvest: Wind-pollinated catkins in spring (April to May); nuts ripen and are harvested in fall, September to October
Hardiness
USDA hardiness zones: 5–9
Temperature: down to -29°C
Troubleshooting
Walnut trouble tends to strike the nuts in summer and the leaves as fall closes in. Jump on the first sign of a pest or blight and you can rescue that year's crop before it hits the ground. Track down the match below, then move fast while it counts.
Black, slimy husks with maggots inside
Blackened, slimy husks with maggots and stained shells hand you the walnut husk fly, whose grubs chew through the husk as it rots. Get yellow sticky traps up by June, then hit the tree with a bait insecticide the moment the catch turns steady. Rake up and destroy the fallen, infested nuts so no flies carry over to next year.
Fix:
- Monitor with supercharged sticky traps from early summer
- Apply a bait insecticide spray at first sustained fly catch
- Pick up and destroy fallen, infested nuts
Frass in the entry holes and nuts dropping early
Frass at a neat entry hole and early nut drop point straight to codling moth, whose larvae tunnel deep into the kernel. Hang pheromone traps in mid-March, ride the degree-days to time sprays after biofix, and roll out mating disruption across the orchard. Sweep up the infested drops and mummies to shut down the next generation.
Fix:
- Use pheromone mating disruption in the orchard
- Time insecticide sprays by degree-day models after biofix
- Remove infested drops and mummies
Slick black blotches spreading over baby nuts and fresh shoots after spring rain
Greasy black spots racing across young nuts, catkins, and shoots in a wet, mild spring flag walnut blight, a bacterium that can wipe out a big slice of the crop. Time copper-based bactericide with a leaf-wetness model and fling the canopy open so it dries fast. Grab a later-leafing cultivar to skip the wettest stretch entirely.
Fix:
- Apply copper-based bactericide sprays timed by a wet-weather model
- Improve air movement and avoid overhead wetting
Yellowing, spotted leaves raining down well before fall arrives
Dark angular spots that snowball into early leaf drop call out anthracnose and its leaf-spot cousins, cranked up by a wet spring or a drought-stressed summer. Rake up and destroy the fallen leaves to slash the spores that overwinter. Pour on a deep watering through dry spells and the tree stays tough enough to shrug it off.
Fix:
- Rake and destroy fallen leaves to reduce inoculum
- Water deeply during dry spells to limit stress
Toxicity
The shelled nuts are a joy to eat and safe for people, but a few parts of the tree call for a careful eye. The wood and shavings pack juglone and cause laminitis in horses, and a moldy fallen nut can trigger tremors and seizures in dogs. Rake up the drops, toss anything moldy, and never bed a horse on walnut shavings.
Toxic to
Cats · Dogs · Horses · Rabbits · Livestock · Birds
Safe for
People
Cats Caution
A shelled kernel will not poison a cat, though all that fat can still spark vomiting and a loose stomach. Keep fallen and moldy nuts out of reach, since the mold on a walnut packs the very toxins that set off tremors.
Dogs Caution
Plain kernels are not systemically toxic, yet a whole nut can choke a dog or jam the gut, and the fat alone often kicks off vomiting. The real danger is a moldy walnut snatched off the ground, which can fire off muscle tremors and seizures within hours.
Horses Severe
Walnut shavings used as bedding cause laminitis. Watch for a reluctance to move, swollen lower limbs, heat in the hooves, and a pounding digital pulse, sometimes within a day of contact, and keep walnut wood or sawdust nowhere near a stable.
Rabbits Caution
Walnuts have no business in a rabbit's diet. That rich, fatty kernel throws a gut built for grass and hay off balance, so keep the nuts and hulls clear of any hutch.
Livestock Caution
Grazing animals do best fenced off from fallen walnuts and hulls. The fatty nuts can sour the rumen, and a pile of moldy drops packs the same mycotoxins that harm dogs.
Birds Caution
A small piece of plain kernel suits some birds, but the fat piles up fast and a moldy nut is dangerous. Serve only fresh, unspoiled bits and clear away anything that has fallen and started to rot.
People Shelled nuts safe
Shelled walnuts are a wholesome food and safe to eat. Just toss any nut that smells musty or shows mold, and keep the staining hulls and walnut sawdust off your skin.
Keep fallen nuts and hulls raked up, discard any moldy nuts, and never use walnut shavings or sawdust as horse bedding.
Helpline numbers
United States
ASPCA Animal Poison Control: (888) 426-4435 (fee applies)
United Kingdom
Animal PoisonLine: 01202 509000 (fee applies)
Australia
Animal Poisons Helpline: 1300 869 738
Varieties
A handful of standout cultivars cover most home and orchard plantings, and these are the names worth chasing down.
'Chandler'
'Chandler' leads the lateral-bearing English walnuts, cranking out heavy yields of light, clean kernels, and its late leafing ducks the worst of the spring frost.
'Franquette'
'Franquette' is a late-leafing French cultivar that bears on its terminals and doubles as a rock-solid pollinizer on cooler, frost-prone sites.
Black walnut (Juglans nigra)
Black walnut is the native North American powerhouse with darker, hard-shelled nuts and prized timber, and it drives most of the juglone, hits horses hard, and anchors English walnut as the usual rootstock.
'Carpathian'
'Carpathian' is a cold-hardy strain of English walnut, tough enough to power through winters down to roughly USDA zone 5.
Companions
Walnuts make life hard for juglone-sensitive plants in their root zone, so the best neighbors are the few species that shrug off juglone and grow happily beneath the canopy.
Keep apart
tomato: Solanaceous crop highly sensitive to juglone; wilts and dies within the walnut root zone.
potato: Juglone-sensitive; stunts and yellows near walnut roots and hulls.
apple: Apple trees decline and can die from juglone exposure near walnuts.
blueberry: Highly juglone-sensitive; foliage yellows and plants collapse near walnuts.
How to propagate
Walnuts start from a graft when you are after a known crop, or from seed when the nut itself is the prize, though seed drags its feet and never copies the parent.
GraftingDemanding
Late winter to spring (bench grafting or field budding) · About 4-7 years to a meaningful nut crop
Almost every named walnut launches from a graft. Growers fuse an English walnut scion onto black walnut or Paradox rootstock in late winter or spring to grab the vigor and pest tolerance those roots deliver, and the young tree needs about 4 to 7 years to crank out a meaningful nut crop.
SeedModerate
Sow stratified nuts in fall, or cold-stratify and sow in spring · Seedlings may take 8-12 or more years to bear and are used mainly as rootstock
Seed is the easy route, but it plays slow and keeps you guessing. Cold-stratify the nuts for about 90 to 120 days and sow in spring, or drive stratified nuts straight into fall ground. The seedlings break from the parent cultivar and can take 8 to 12 years or more to bear, so most end up as rootstock for grafting.
Myths
Planting anything under a walnut is a lost cause.
True, the tree fires off juglone, and it does knock back sensitive plants like tomato, potato, apple, and blueberry, but mostly within the drip line. Loads of species tolerate juglone and grow strong nearby, so the ground under a walnut is anything but a dead zone.
A dog can happily munch walnuts with zero risk.
A plain kernel will not poison a dog, but it is rich enough to churn the stomach, and a whole nut can choke or block the gut. The real danger is a moldy walnut, loaded with mycotoxins that fire off tremors and seizures.
Sprout a walnut in the ground and the same great nuts come back.
Named English walnuts ride on black walnut or Paradox rootstock, so the seed inside a nut never breeds true. A seedling is a roll of the dice, throwing variable nuts and stalling many years before it bears.