Tree · Juglandaceae
Walnut
Juglans regia
With deep, rich soil and open sun, a walnut forgives your early mistakes, shades the yard for generations, and fills 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 grown as much for the nuts it drops as for the calm it brings to a yard. It belongs to the walnut family and can reach 60 feet (18 m) with a wide, open crown, so it really does want a space of its own. Give it deep, fertile soil and plenty of sun, and it will crop and shade for generations, even if you are only just starting out.
The English or Persian walnut, grown for its kernels, is the one most people plant, while the native black walnut is its hardier cousin, loved for hard-shelled nuts and dark timber. Both trees make a compound called juglone that seeps from roots and hulls and can hold back a few sensitive plants nearby. Knowing that early simply helps you choose a good spot and pick what to grow beneath it.
More than anything, a walnut asks for patience, and that is good news for a nervous grower. A grafted tree takes several years to bear, and the falling nuts with their staining hulls do make a mess on paving, so plant it well clear of the house and walks. Get the spot right and the tree does the rest, giving back shade, structure, and a steady fall harvest.
Care
The short version: give it full sun and deep, well-drained loam, water it deeply while it is young, then only now and then once it settles in. Feed in early spring, prune in late summer so it doesn't bleed sap, and leave it plenty of room.
Light
Walnuts love full sun and only put up with light partial shade. A tree hemmed in by buildings or bigger trees tends to grow lopsided and set far fewer nuts, so give yours open sky all around and it will thank you.
Water
While a tree is young, water it deeply every 1 to 3 weeks through those first few seasons so the roots settle in well. Once it is established a walnut copes fairly well with drought, but it still gives its heaviest crop when you offer a good deep soak now and then through a dry summer.
Soil
Plant into deep, fertile, well-drained loam and your walnut will feel right at home. A pH of 6.0 to 7.5 suits it nicely, and the one thing it can't forgive is wet feet, so steer clear of soggy or shallow ground where the roots have nowhere to run.
Temperature
A walnut is tough and takes a wide swing of weather, from about -22°F to 95°F (-30°C to 35°C). The one thing to watch is a late spring frost nipping the young growth and catkins, which is exactly why later-leafing cultivars give you a little edge in colder spots.
Humidity
Ordinary outdoor humidity of 40% to 70% is perfectly fine for a walnut, so this is nothing to fuss over. Damp, still air in a wet spring can feed blight though, so an open canopy that dries quickly matters far more than any reading on a gauge.
Feeding
Feed in early spring before the new growth pushes, using a nitrogen-focused balanced fertilizer guided by a soil or leaf test. Walnuts are hungry for nitrogen, but a quick test first saves you guessing, since anything extra just washes away.
Pruning
Train a young tree to a single central leader, then gently thin out dead, crossing, and low limbs as it grows. Do the work in late summer or early fall, because a walnut bleeds sap heavily from cuts made in late winter and spring, and timing it right spares the tree that stress.
Repotting
A walnut is a landscape and orchard tree rather than a pot plant, so once it is in the ground there is no repotting to worry about. If you do hold a young tree in a nursery pot too long, keep an eye out for roots circling the pot and stalled top growth, and get it planted out.
Size & spacing
Picture a big tree in time, 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 has room to open and the staining nuts don't drop on paving below.
When to plant
A walnut follows the seasons, and it likes to go in while it is still resting. Set bare-root or balled trees out in late winter to early spring, enjoy the wind-pollinated catkins that appear in spring, and gather the ripe nuts in fall once the hulls begin to split.
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
Most walnut worries land on the nuts in summer or the leaves toward fall, and the good news is that early action usually saves the crop. Take a calm look at what you are seeing, match it to the notes below, and step in while it still makes a difference. None of this is beyond a first-time grower.
Blackened, slimy husks with maggots inside
Those soft, blackened husks with little maggots are the work of the walnut husk fly, whose grubs feed in the husk and stain the shell as the tissue rots. Hang yellow sticky traps by June, and once you start catching flies steadily, spray a bait insecticide. Rake up and get rid of the fallen, infested nuts so the flies can't carry over into 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-packed holes and nuts falling early
When you spot frass at a neat entry hole and nuts dropping too soon, codling moth larvae have bored straight into the kernels and spoiled them. Set pheromone traps in mid-March, follow degree-days to time your sprays after biofix, and think about mating disruption across the orchard. Clearing away the infested drops and old mummies keeps the next generation from building up.
Fix:
- Use pheromone mating disruption in the orchard
- Time insecticide sprays by degree-day models after biofix
- Remove infested drops and mummies
Greasy black spots on young nuts and shoots after wet weather
Greasy black patches on young nuts, leaves, and shoots during a wet, mild spring point to walnut blight, a bacterium that can knock down a good share of the crop. Time your copper-based bactericide sprays with a leaf-wetness model, and keep the canopy open so it dries fast. Choosing a later-leafing cultivar helps you sidestep the wettest stretch altogether.
Fix:
- Apply copper-based bactericide sprays timed by a wet-weather model
- Improve air movement and avoid overhead wetting
Yellowing leaves with dark blotches dropping in late summer
Dark, angular spots that lead to early leaf fall usually mean anthracnose and related leaf-spot fungi, made worse by a wet spring or a drought-stressed summer. Rake up and destroy the fallen leaves to cut back the spores that overwinter. A good deep watering through dry spells keeps the tree strong enough to shrug the trouble off.
Fix:
- Rake and destroy fallen leaves to reduce inoculum
- Water deeply during dry spells to limit stress
Toxicity
The shelled nuts are lovely to eat and safe for people, but a few parts of the tree do ask for care. The wood and shavings carry juglone and can cause laminitis in horses, and a moldy fallen nut can bring tremors and seizures in dogs. Rake up the drops, bin anything moldy, and never bed a horse on walnut shavings, and everyone stays safe.
Toxic to
Cats · Dogs · Horses · Rabbits · Livestock · Birds
Safe for
People
Cats Caution
A shelled kernel is not going to poison a cat, but all that fat can still upset the stomach and cause vomiting. Keep any fallen or moldy nuts out of paw's reach, because the mold on a walnut carries the very toxins that trigger tremors.
Dogs Caution
Plain kernels aren't systemically toxic, yet a whole nut can choke a dog or lodge in the gut, and the fat on its own often brings on vomiting. The real worry is a moldy walnut picked up off the ground, which can trigger muscle tremors and seizures within hours.
Horses Severe
Walnut shavings used as bedding bring on 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 well away from any stable.
Rabbits Caution
Walnuts really have no place in a rabbit's diet. The rich, fatty kernel can upset a gut that is built for grass and hay, so keep the nuts and hulls away from any hutch.
Livestock Caution
Grazing animals are best kept off fallen walnuts and hulls. The fatty nuts can sour the rumen, and a heap of moldy drops carries the same mycotoxins that harm dogs.
Birds Caution
A small piece of plain kernel suits some birds, but the fat adds up quickly and a moldy nut is dangerous. Offer only fresh, unspoiled bits and clear away anything that has fallen and begun to rot.
People Shelled nuts safe
Shelled walnuts are a healthy, welcome food for people. Bin any nut that smells musty or shows mold, and keep the staining hulls and walnut sawdust off bare 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
Just a few walnut cultivars cover most gardens and orchards, and getting to know them by name makes choosing an easy, friendly first step.
'Chandler'
A leading lateral-bearing English walnut, 'Chandler' is loved for heavy yields of light, clean kernels, and its late leafing helps it slip past the worst spring frosts.
'Franquette'
'Franquette' is a late-leafing French cultivar that bears on its terminals and earns its place as a dependable pollinizer on cooler, frost-prone sites.
Black walnut (Juglans nigra)
Black walnut is the native North American species with darker, hard-shelled nuts and prized timber, and it is the main source of juglone, harmful to horses, and the usual rootstock beneath English walnut.
'Carpathian'
'Carpathian' is a cold-hardy strain of English walnut, tough enough to come 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 are grafted when you want a known crop, or grown from seed when the nut itself is the point, though seed takes its time and never quite copies the parent.
GraftingDemanding
Late winter to spring (bench grafting or field budding) · About 4-7 years to a meaningful nut crop
Nearly every named walnut begins life as a graft. Growers join an English walnut scion onto black walnut or Paradox rootstock in late winter or spring for the vigor and pest tolerance those roots give, and the young tree needs about 4 to 7 years to reach 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
Growing from seed is easy but slow and full of surprises. Cold-stratify the nuts for about 90 to 120 days and sow in spring, or plant stratified nuts straight into fall ground. The seedlings won't match the parent cultivar and can take 8 to 12 years or more to bear, so most are used as rootstock for grafting.
Myths
A walnut tree poisons everything planted near it.
The tree does give off a compound called juglone that troubles sensitive plants like tomato, potato, apple, and blueberry, but mostly within the drip line. Plenty of plants tolerate juglone and grow happily nearby, so the ground beneath a walnut is far from a dead zone.
Walnuts make a safe, healthy snack for dogs.
A plain kernel won't poison a dog, but it is rich enough to upset the stomach, and a whole nut can choke or block the gut. The real danger is a moldy walnut, which carries mycotoxins that bring on tremors and seizures.
Plant a walnut from seed and you'll harvest the same variety.
Named English walnuts are grafted onto black walnut or Paradox rootstock, so the seed inside a nut simply won't breed true. A seedling is a gamble that grows variable nuts and takes many years to bear.