For years we had a cashew tree growing in the Economic section of Foster Botanical Garden. This section is where plants with economic value or potential are grown; they include herbs, spices, medicines, food and even poisons.
The main thing we were taught about cashews is to handle them with extreme care. If they are not ripe enough (or too ripe) — abunai! (Japanese for danger). It is difficult — and possibly toxic — to harvest and process the hard-shelled seeds (nuts). You need to harvest them at just the right time, and then extract the seed carefully. The juice from the shell around the fruit might burn your skin.
That’s why I’m happy to buy this heart-healthy nut at the store!
Cashew trees are mainly grown commercially in Brazil and India.
The Latin name is Anacardium occidentale, and it is in the mango family, Anacardiaceae. Cashews are native to Brazil and Tropical America. Relatives include fruit trees such as mango, wi or Otaheite apple and hog plum (my honey’s favorite). Poisonous relatives include poison ivy and sumac, and the marking nut tree.
Interestingly, researchers are looking into whether the toxic principles in the cashew’s shell might make a good insecticide.
A cashew tree’s flowers are greenish yellow, fragrant and grow in panicles (cluster of flowers on branches). The trees can grow up to 40 feet in ideal conditions, though we usually find shorter, wider trees here in Hawaii.
The fruit and nut are very interesting to see. The “fruit” that catches our eye is actually a pseudocarp, or false fruit. Some call this a “cashew apple.”
Botanically speaking, the actual fruit of the cashew tree is a yellow or red kidney-shaped drupe (fleshy fruit) that grows at the end of the cashew apple. The drupe develops first on the tree, and then the pedicel (a small stalk bearing an individual flower) expands to become the cashew apple. The true fruit contains a single seed, which is generally considered to be a nut.
While bees pollinate its flowers, the colorful and juicy fruit is an adaptation to attract fruit-eating animals to aid in seed dispersal.
Aren’t plants wonderful and complex?
Although it is perishable, we can eat the fruit and make value-added products such as wine and fruit roll-ups.
Cashew trees favor well-drained soils and regular watering to get established. The flowers like it dry, just like mangoes. They benefit from leafy mulch. Keep turf grass well away from the root zone.
A FEW years ago, I went to an event at Reppun Farm where I saw a gorgeous cashew tree loaded with ripe fruit. It got me thinking it might be a good crop to grow more of in Hawaii, especially if we cultivated it like old-time Hawaii farmers did, or use modern practices such as permaculture and regenerative agroforestry.
That is, grow a diversity of tree species, not a single monoculture (plantation style). Layers of tall and short trees, shrubs and groundcovers are all grown together. This diversity keeps the plants and soil healthy, and helps capture rainwater and let it percolate down to our aquifer.
Recently my friend Kaui Lucas, a trained permaculturist, showed me some cute keiki cashew trees she is growing on her sunny lanai, protected with chicken wire. They’d grown from seeds Lucas scored from Hinshaw Farms on Oahu.
“Frank Hinshaw is the cashew guy,” she said. “He invited me to go visit, we could make a holoholo day out of that. Super sweet guy and he was so helpful.”
An email from the Department of Agriculture had alerted her to the seed giveaway.
On Kauai, Neu Mana Hui Farm — which was established in 2002 — has more than 200 cashew trees. Owners Linda and Scott Neuman have found out which varieties grow best and how to harvest, dry and roast the nuts. They are a major local producer of organic cashew nuts and related value-added products; you can check them out online at cashewnutshawaii.com.
Heidi Bornhorst is a sustainable landscape consultant specializing in native, xeric and edible gardens. Reach her at heidibornhorst@gmail.com.
