Cashew trees are evergreen tropical trees which can grow up to 40 feet high. Branches spread widely in an umbrella-like shape and may even droop down to touch the ground, where they can send out new roots. Attractive pink flowers grow in clusters and precede the dual fruit, which consists of the cashew nut, a kidney shaped grey fruit, and the cashew apple, which is actually the swollen stem. Closely related to mangoes and pistachios, trees produce large, oblong, shiny leaves near the end of branches. Usually trees will start producing nuts within 3 years, and harvests can continue for as long as 30–50 years.
There are not many named varieties of cashew trees, in part because it cross pollinates easily and is mostly grown from seed. Therefore, each seedling will be slightly, or very, different from its parent tree. Trees are mostly differentiated by the color of their cashew apples: most often red or yellow.
Seed: Only seeds which sink in a container of water should be planted. Avoid handling seeds with bare skin. Cashew trees grown from seed do not “grow true” or necessarily have the same characteristics as their parent plant, and it will take around 3 years for trees to begin producing a harvest. However, this is still the most common way of propagating cashews and if you want to take a stab at growing cashews from seed:
Seed Depth: Surface to 3″
Space Between Plants: 30′ final spacing.
Space Between Rows: 30–35′
Germination Soil Temperature: 72–80°F
Days for Germination: 4–10
Sow Indoors: At any time.
Sow Outdoors: After all danger of frost has passed.
Vegetative: Commonly propagated by grafting or layering.
Grows well in a tropical climate. Daytime temperatures above 50°F are necessary, with ideal averages around 75–80°F. Fairly drought resistant and heat tolerant, most trees are grown within 25° latitude north or south of the equator. Not frost tolerant. Excessive moisture during the flowering phase can result in low yields.
Natural: Full sun. Germinating seedlings and young trees should be started in partial shade and gradually hardened off to adjust to full sun.
Artificial: Seedlings will grow well under LED or fluorescent lamps. Switch to a high pressure sodium HID lamp for larger trees. Provide at least 12 hours of light per day.
Soil: Grows best in well-drained sandy or loamy soils. Tolerant of a wide range pH between 4.5 and 8.5.
Soilless: Container-grown trees should be planted in a free draining mix of pine bark, well-rotted manure, and vermiculite. Germinate seeds on or just under the surface of a pine-bark-based soilless mix.
Hydroponics: Not much is known about growing cashews hydroponically, so if you try it out, let us know how it goes!
Water: Requires low to moderate levels of water. When trees are young, they’ll need regular moisture. Mature trees can survive drought due to their deep root system. However, fruit and nut quality and yields will be improved with regular water. You should always let the soil surface dry out between watering to avoid soggy roots. Aim for about 1 inch per week during dry and hot weather.
Nutrients: Requires low to moderate levels of nutrients. Can tolerate poor soils, but will have a higher yield with more fertile soil or occasional applications of a balanced organic fertilizer. In particular, plants need adequate amounts of nitrogen, phosphorus, and zinc.
Foliar: Will benefit from foliar applications of zinc. Spraying with an extract derived from moringa leaves every two weeks can help protect plants from fungal diseases.
Pruning: Minimal pruning is needed. Remove any dead or damaged branches. Pruning the top of the tree back after 5 or 6 years of growth will make it easier to harvest by keeping trees bushy and shorter.
Mulching: Use mulch to conserve soil moisture. You can use fallen leaves that are either green or dried.
Deficiency(s): A nitrogen deficiency will cause slow growth and reduced yields. Magnesium, potassium, and phosphorus deficiencies can cause low yield and poor quality nuts.
Rotation: Since trees have such a long lifespan, rotation will not be a concern!
Companions: Grows well with rice, corn, cassava, pineapple, and legumes when practicing inter-cropping. Can also be planted with coconut trees. Avoid planting with cotton or sweet potato.
Harvest: Pick fruit when ripe, usually starting in the winter or dry season. Fruits will continue to mature for 2–4 months, beginning about 2 months after the flowers bloom. When it is ready, the cashew apple will be pink or red (sometimes yellow) and the shell of the nut will turn dark grey. Collect any fruits that have fallen, as they are already ripe. Separate the fruit part from the nut part for processing. Dry nuts for several days or store for up to 2 years before processing. Roast nuts before cracking them to get rid of the toxic oils found in their skins.
Storage: Whole nuts can stay fresh awaiting processing for up to 2 years if dried and stored in a cool and dry location. Once nuts have been hulled and processed, it’s best to use them within 6–9 months or up to a year if kept in the refrigerator. The fresh cashew apple does not store well and is best used within a few days of harvesting.
The world’s largest cashew tree has a rare genetic mutation that causes 4 of its 5 main branches to grow laterally and sprout new roots anywhere they touch the ground. It now covers an area of between 7,300 and 8,400 square meters in Pirangi do Norte, Brazil, and makes as many as 60,000 fruits and nuts per year!
Preserve: Cashew nuts can be made into a nut butter by grinding them finely. This spread should be refrigerated and used within 6 months. Cashew apples can be made into a vinegar, or alcohol, through fermentation. The fruit is also used for making preserves, chutneys, juices, or jams which can be canned for later use. It can also be dehydrated and candied, a practice popular in Costa Rica.
Prepare: The cashew nut needs to be hulled before it’s ready to eat, but the shell is infused with a toxic oil which will cause blistering and other unpleasant skin reactions. To avoid getting this on your skin or on the edible inner nut, whole un-shelled cashews are usually roasted or steamed to neutralize the oil before shelling. You can also deep freeze them and then separate the nut from the shell while still frozen. Wear gloves, safety goggles, and other protective clothing for this process. Processed nuts are eaten as a snack, either raw or roasted. They can also be made into a vegan cheese alternative, added to curries, baked into dessert recipes, or used as a cereal topping. The cashew apple can be eaten raw as a fruit, though it has some astringency. Cooking briefly by boiling or steaming will remove this, and peeling can also help since tannins are concentrated in the skin. It can also be added to recipes like a vegetable.
Nutritional: The nut of this tree provides a good source of calories, dietary fiber, and healthy mono-unsaturated fatty acids. Also contains vitamin K, many B-complex vitamins, manganese, potassium, copper, iron, magnesium, selenium, and zinc. The cashew apple contains high levels of vitamin C.
Medicinal: Regular consumption of cashew nuts may provide health benefits to the eyes. The skin of the nuts and leaf extracts may have antibacterial and antifungal properties. Historically used as a fever reducer, blood pressure regulator, and in the treatment of snakebites. The high levels of antioxidants found in the nut are beneficial to overall health. Fruit juices and oils of the nut are used topically to treat warts and calluses. Leaves may be used for treating toothaches.
Warnings: Cashew nuts can provoke an allergic reaction in some individuals. Use caution, especially if you have known allergies to other tree nuts. The shells of the nut contain a toxic oil which can cause skin reactions including blistering. Use gloves when you are picking or processing fruits or nuts. Roasting or steaming will get rid of this chemical.
You’ll never need to be sad about giving up dairy cheese once you’ve learned to make this Cultured Cashew Cream Cheese.