Cashew Nut Tree Plant Profile (Anacardium occidentale)

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The cashew nut tree is one of the most interesting nut/fruit trees you can grow. Most people don’t realise how weird the fruit is until they see one in real life. The actual nut grows outside the fruit, like it’s hanging off the bottom. It’s a tropical tree, and it needs a warm climate, but if you’ve got the space and patience, it’s well worth growing. Just don’t expect to eat a handful of homegrown cashews anytime soon – it's a bit of a process.

Climate

Cashews grow best in tropical and warm subtropical climates. They need long, hot summers to fruit properly. If you’re in coastal Queensland or anywhere frost-free north of Brisbane, you’re in the right zone. They hate frost. Even a light frost can kill a cashew tree when it's young. They won't grow well in cool weather, so if you’re further south, it’s probably not the right tree. You could try growing one in a large pot so you can move it to a warm spot in winter, but cashews are a big tree and you might find you won't get them to fruit unless they're in the ground.

Soil

Cashew nut tree seedling when I bought it

Cashews don’t need perfect soil. They prefer sandy, slightly acidic soil that drains well. Heavy clay is a no-go unless it’s been well improved and drains freely. They’re often grown in poor soils overseas, so fertile soil isn’t the biggest issue, but drainage is. If water sits around the roots, they’ll rot.

Sun and Water

Full sun is a must. They won’t fruit properly in shade. Cashew trees are drought-tolerant once they’re established, but they need water in the early years. During long dry spells, watering deeply every few weeks helps keep them healthy. They don’t like wet feet, so don’t overdo it, and make sure the soil drains well. A thick layer of mulch (affiliate link) helps regulate moisture and protects the surface roots.

Size and Spacing

The cashew nut tree seedling after about 3 years — The seedling after about 3 years

Cashew trees grow around 6 to 12 metres tall, depending on conditions, but you can keep them smaller with pruning (#ad). In a home garden, most people keep them under 4 metres. My tree is around 5 years old, in a crappy spot, and it's about 3 metres tall. The canopy spreads out wide, so give it space. Plant it away from paths – fallen fruit can be messy, and the seed (#ad) pods stain!

Propagation

Cashew trees are usually grown from seed (#ad). Use fresh, raw seeds (#ad) (not the roasted ones from the shop). Sow them on their sides in a loose, well-draining seed raising mix. They germinate in a few days to a couple of weeks. You can also grow them from grafted or air-layered trees if you want faster fruiting, but it’s harder to find these in Australia. Daley's nursery is a good place to start. Territory Native Plants could be worth a go, too, and their photos are worth a look.

Once sprouted, they grow pretty fast in warm weather. Keep them sheltered from wind while they're young – they can be a bit brittle until they harden off.

Fruit and Harvesting

Cashew Nut Tree (Anacardium occidentale) apple closeup with nut hanging underneath

The part most people call the “cashew fruit” is actually the swollen stem or receptacle. It’s called the cashew apple. It’s yellow or red and very juicy, but it doesn’t store well. You won’t find it in shops because it ferments fast and bruises easily. You can eat it fresh (if you don’t mind astringent fruit) or juice it, though it’s an acquired taste.

The nut itself hangs off the bottom of the fruit and comes in a hard, toxic shell. You can’t eat it raw. It contains anacardic acid, which is similar to poison ivy and causes burns if you don't handle it carefully. To eat a homegrown cashew, you need to dry the nut, roast the outside to release the toxins, crack it open, and then roast the kernel again. It’s a lot of effort for one nut! Satisfying though, if you’re up for the challenge.

Uses

The tree is useful beyond just the nuts. It gives some shade, handles wind well, and can help stabilise soil in sandy areas. The wood is sometimes used for firewood or small timber projects. You can eat the apples fresh, juice them, or ferment (#ad) them into alcohol. They're best eaten straight after picking. You can also feed the apples to livestock if you're not eating them yourself.

Traditional and Medicinal Uses

Cashew trees have been used for a long time in traditional medicine. In Brazil and West Africa, the bark and leaves are used for digestive problems and infections. Some people make a tea from the bark or leaves for sore throats or diarrhoea. The apple juice is also used to treat mouth ulcers and throat infections, and in some countries it’s fermented into alcohol or vinegar.

The oil in the shell (called cashew nut shell liquid) is caustic, but it also has antimicrobial and insect-repelling properties. It’s been used in traditional remedies for skin issues, though it must be handled very carefully. In Ayurvedic medicine, cashew bark and leaves are used to reduce inflammation and support digestion.

These aren’t uses I’d recommend trying without knowing what you’re doing, but it’s interesting to know how widely the tree has been used. As always, consult with a health professional before using it as medicine.

Caution

Be careful with the shell! Wear gloves if you’re handling fresh nuts. The oil inside is caustic and can cause skin burns. Don’t roast them indoors – the fumes can be harmful. Most people grow cashew trees for the interest and shade, rather than for large nut harvests. One or two trees can give you a handful of nuts per season once they're mature.

They are an awesome talking point in your garden – this is one of the trees everyone wants to look at when it's fruiting!