Anacardium occidentale Seeds | Cashew
LATIN NAME: Anacardium occidentale
COMMON NAME: Cashew
Plant Profile
Anacardium occidentale is grown for a seed that comes with a hazard attached. The nut hangs below a swollen, fleshy stalk that looks like a fruit and is not: the cashew apple is the enlarged pedicel, and the true fruit is the kidney-shaped shell above it. The tree is evergreen, low and spreading, five to twelve metres, with leathery leaves and small pink flowers in a panicle.
The species is native to the dry coastal woodlands of north-eastern Brazil, and it was carried to India and to East Africa by the Portuguese in the sixteenth century. India, Vietnam, Nigeria and Brazil are now the main producers. The tree tolerates poor sand and a long dry season, and it fruits within three years, which is why it is a smallholder crop as much as a plantation one.
Science & Biotechnology
The shell contains a phenolic oil, cashew nut shell liquid, made up of anacardic acid, cardol and cardanol. These compounds are closely related to the urushiol of poison ivy, and touching the raw shell causes a severe, blistering rash that in India is called cashew itch. The oil is driven off by roasting, and the nuts are then shelled, which is why cashew processing is a skilled and dangerous job.
The same liquid is valuable in its own right. Polymerised, it makes a friction dust for brake linings and a resin for varnishes and for oil-resistant coatings, and cardanol is used in epoxy formulations. The cashew apple is edible but perishable, and its juice is fermented or distilled in Brazil and in Goa, since it bruises within a day of picking and cannot be shipped.
Uses & Benefits
The kernel is eaten roasted and salted, and it is one of the most traded tree nuts in the world. The shell liquid goes to brake linings, to varnishes and to plastics, and the apple is used for juice, for jam and for a spirit called feni in Goa.
In medicine the bark and the leaf are used as an astringent and the kernel oil for skin complaints, and the apple is used for a cough syrup in Brazil. The tree is also planted for shade and for sand stabilisation, and the wood is used for boxes and for boats, though it is not durable.
Growing from Seed
Seed is sown fresh, since it loses viability within a few months. Sow the nut on its side, one per deep pot, at 25 to 30 degrees; germination is in two to four weeks. The seedling has a long taproot and should be planted out when it is thirty centimetres high.
The tree wants full sun, a long dry season and sandy, well-drained soil. It is tender below about minus one, so it needs a frost-free climate. Plant it where there is room for a crown six metres across, and do not irrigate heavily, since the tree fruits best with a marked dry spell before flowering. Handle the shells outdoors and with gloves.
Our Take
A nut that comes with a caustic oil and a fruit that will not travel. Grow it in the tropics for the apple as much as for the kernel.
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