Tree · Anacardiaceae
Cashew
Anacardium occidentale
A tropical tree that hands you two harvests in one, the cashew apple and the nut, as long as its roots stay warm, sunny, and well drained.
Full sun
Every 7–14 days
USDA 10–13
20–39 ft · 6–12 m
Overview
The cashew is a fast-growing tropical tree, a cousin of both poison ivy and the mango, that started out in the warm lowlands of Brazil and now flourishes across the frost-free tropics. It runs on real heat and folds in the cold, so it holds only in the warmest zones where frost never reaches. Give it room and it powers into a wide, spreading tree that can clear 40 feet (12 m), with a canopy just as broad.
What hangs from the branches throws a lot of people. The fleshy red or yellow piece everyone spots is the cashew apple, a swollen stalk rather than the true fruit, and the kidney-shaped nut dangles below it on the outside. That nut is the payoff, though its shell carries a caustic oil that has to be cooked off before you can eat the kernel inside.
For such a big tree, the cashew asks for surprisingly little once it settles in. It races ahead in poor, sandy ground that stalls fussier trees, and it shrugs off drought after the first few years. The one thing it flatly refuses is wet feet, so drainage outranks fertility from the day you plant it.
Care
The short version: give it full sun and deep, sandy, fast-draining soil. Water steadily while it is young, then ease off as it matures. Keep it warm and frost-free, and never let the roots sit in soggy ground.
Light
Cashews crave full sun and crop poorly in shade, so give yours an open, bright spot with nothing crowding the canopy. Pour on the light and the flowers and nuts keep coming.
Water
Water young trees often to get them rooted, then pull back hard, because a mature cashew is highly drought tolerant and hates soggy ground. Let the top half of the soil dry between drinks, around every 7 to 14 days, and always lean toward the dry side.
Soil
Plant it in deep, well-drained sandy or sandy-loam soil, even the poor, low-fertility ground that stumps other trees. A pH of 5.0 to 6.5 hits the mark, and fast drainage beats rich earth every time.
Temperature
This is a true tropical tree, thriving from 50°F to 104°F (10°C to 40°C) and finished off by frost. Grow it only where the cold never bites, in tropical or frost-free subtropical climates.
Humidity
Cashews enjoy air on the humid side, around 50% to 80%, mirroring the tropics they come from. Even so, keep the canopy open so the leaves dry fast, since trapped damp invites disease.
Feeding
Feed through the warm growing season with a balanced NPK carrying nitrogen, phosphorus, and potassium, and add zinc where the soil runs short. One seasonal feeding fuels this tough tree just fine.
Pruning
Train a young tree to a single strong leader, then clear out the dead, diseased, crossing, and low branches. Opening the canopy gets air moving through, your sharpest defense against the fungal diseases cashews tend to catch.
Repotting
A field-grown cashew settles in for the long haul, but a potted one wants a bigger home every 2 to 3 years. Watch for roots circling the pot, water shooting straight through, or growth that stalls, all signs it has outgrown its spot.
Size & spacing
A common cashew shoots up into a wide tree of 20 to 40 feet (6 to 12 m) tall and nearly as broad, so give it serious room. Set it well clear of buildings, paths, and power lines, since the canopy can fan out to 33 feet (10 m) across.
When to plant
Cashew follows the tropics, not a temperate calendar. Get the nuts going in nursery bags a couple of months early, move the young trees out once the soil warms and frost has passed, then watch for flowers in the dry season with nuts and apples arriving a few months on.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: Seeds sown in nursery bags 2 to 3 months before transplanting in warm climates
- Plant: After all frost danger when soil is warm; tropical and frost-free subtropical regions only
- Harvest: Flowers in dry season; nuts and cashew apples harvested several months later, typically late dry season
Hardiness
USDA hardiness zones: 10–13
Temperature: down to -1°C
Troubleshooting
Most cashew trouble strikes the new growth, the flowers, or the roots, and damp weather usually drives it. Catch it early and a fungicide or sharper drainage puts the tree back on course quickly. Find your symptom below and act on it before it spreads through the canopy.
Black sunken spots racing across leaves and shoots with twigs dying back
Those dark, sunken marks flag anthracnose, a fungus that pounces when warm weather stays wet and the new growth and flower clusters sit damp for hours. Prune out and burn the infected shoots, throw the canopy open so air moves, and bring in a labeled fungicide while the tree flushes and flowers. Space trees wide and keep water off the leaves, and you head off most of it before it starts.
Fix:
- Prune and destroy infected shoots
- Improve canopy air circulation
- Apply a labeled fungicide during susceptible flushing and flowering
Wilting branches and scorched leaves in wet, soggy soil
A cashew wilting and barely fruiting in heavy, waterlogged ground is fighting root rot, not thirst. The roots discolor and the trouble shows right after heavy watering or standing water. Sharpen the drainage, dial back the watering, and on heavy soils plant it up on a raised mound. A mature cashew shrugs off dry spells, so soggy roots are the real enemy.
Fix:
- Improve drainage
- Reduce irrigation
- Plant on mounds in heavy soils
Grayish-white powder dusting the flowers and tender new nuts
A dusty white film on the flower clusters and young nuts points to powdery mildew, which jumps on soft new growth during cool, dry flowering spells. Leave it be and it strips off flowers and tiny nuts and trims your crop. Hit it with sulfur or a labeled fungicide at bloom, snip away the worst clusters, and keep the canopy open so it finds little to grab.
Fix:
- Apply sulfur or a labeled fungicide at flowering
- Remove badly affected panicles
Toxicity
A roasted, shelled cashew makes a fine snack, but the raw nut is a different animal. The shell and the layer wrapping the kernel hold a caustic oil called CNSL, packed with the same urushiol that drives poison ivy, and it burns skin and mouth on contact. Keep raw shells, husks, sap, and prunings away from children and pets, and pull on gloves before you touch them.
Toxic to
Cats · Dogs · Horses · Rabbits · Livestock · Birds
Safe for
People
Cats Caution
The rich, fatty kernel can spark drooling, vomiting, and loose stools, and a cat that licks or bites a raw shell can burn its mouth on the caustic oil. Keep both well out of reach.
Dogs Caution
A few swiped nuts usually mean vomiting and diarrhea, and a bigger helping of the fatty kernel can trigger painful pancreatitis. Chew a raw shell on top of that and urushiol burns hit the mouth and skin too.
Horses Caution
Horses should stay well away from raw shells, sap, and prunings, where the same urushiol that scars human skin can blister the lips and mouth. Keep fallen shells and trimmings cleared from any paddock.
Rabbits Caution
The caustic shell oil and the heavy, fatty nut are both wrong for a rabbit's gut. Offer neither, and watch for soft stools or a stalled appetite if one gets into dropped shells.
Livestock Caution
Cattle, goats, and sheep can scorch their mouths on the raw shell liquid and sour their stomachs on the oily kernels. Fence stock away from the tree and rake up shell waste after harvest.
Birds Caution
Backyard birds should never get raw shells or husks, since the irritant oil burns soft tissue. A crumb of plain roasted kernel now and then does no harm, but the fat does them no favors either.
People Roasted nuts safe
Properly roasted and shelled cashews are a wholesome snack and safe to eat. The raw nut and its shell are another matter, since the urushiol they carry is the same irritant as poison ivy and burns skin and mouth, which is why nobody should handle or eat them unprocessed.
Wear gloves when handling raw shells, husks or sap; never let people or pets contact or chew unprocessed nuts. Roasting in the open can release irritant fumes.
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
Growers sort cashews mainly by size and how fast they bear, and these two broad types cover most of what you will plant.
Common (medium/tall) cashew
The common medium to tall cashew is the classic plantation tree, a big, spreading giant that climbs to 12 m or more and takes its time before it starts bearing.
Dwarf precocious cashew (e.g. anao precoce types)
Dwarf precocious cashews like the anao precoce types are compact selections that flower and fruit within a few years and stay small enough to pack in close and harvest with ease.
How to propagate
Start a cashew from a fresh nut or clone a tree you admire. The route you pick shapes how soon it fruits and how closely it tracks its parent.
SeedEasy
Sow fresh viable nuts in the warm season · Germinates in 2 to 3 weeks; bears in about 3 years
Seed. Sow fresh, viable nuts in the warm season, keeping the ones that sink in water, and the seedlings push up in 2 to 3 weeks. Drop them straight into the ground or into bags, since the long taproot resents being moved once it forms. Seedlings vary from one to the next, and a tree raised this way takes about 3 years to start bearing.
GraftingModerate
Onto vigorous seedling rootstock in warm conditions · Bears in roughly 2 to 3 years
Grafting. Graft a chosen clone onto a vigorous seedling rootstock in warm weather and you get uniform trees that crop sooner. A softwood, cleft, or veneer graft is the go-to, and the tree bears in roughly 2 to 3 years.
Air layeringModerate
Warm humid growing season · Several weeks to root before severing
Air-layering. Air-layering through the warm, humid growing season clones the parent tree. The wrapped stem needs several weeks to root before you cut it free, and it sees far less use than grafting on a commercial scale.
Myths
The cashews labeled raw in stores are truly raw, and any nut straight off the tree is fair game.
Those so-called raw cashews already went through steaming or heat treatment and shelling before they hit the shelf. A nut plucked straight from the tree still carries caustic shell oil, the urushiol and anacardic acid that burn skin and mouth. No cashew is safe to eat or handle until it has been roasted and processed.
The fleshy red or yellow cashew apple is the fruit, with the nut growing inside it.
That plump, juicy cashew apple is no true fruit at all but a swollen stalk, an accessory fruit the tree pumps up below the flower. The real fruit is the kidney-shaped nut that swings outside and below the apple, not inside it.