Like many other Australian trees, the macadamia thrives in Hawaii. Other species that are suited to the islands include grevillea, melaleuca, callistemon and eucalyptus. When it comes to our favourite nut, many people on the mainland think of macadamia nut trees as native to Hawaii, but here we know it is an Australian tree that we have adopted as our own.
Scientists at the University of Hawaii took the wild forms and developed the many improved varieties we have today. We use the nut in many local dishes, especially desserts. We even use the leaves for holiday decorations instead of holly.
When the first humans arrived in Hawaii, edible nutritious seeds or nuts were hard to find. The only native nut was the mahoe, or Alectron macrococculus. Polynesians then brought with them the coconut and the kukui nut. Technically, the coconut is not a true nut. Although the kukui nut is edible, it can cause serious stomach problems if eaten in large quantities, as it is related to the castor oil plant. So in terms of food and nutrition, true nuts were lacking.
In the 20th century, researchers at the University of Hawaii College of Tropical Agriculture literally scoured the tropical world for nut crops that could adapt to some of Hawaii’s diverse climates. Many nut-bearing species were introduced, such as almonds and cashews, but none became as popular as the Australian macadamia nut.
Although the first macadamias arrived here in the late 1800s, it took years for them to be seriously considered as a commercial crop. Subsequently, researchers developed many superior varieties, and it wasn’t long before farmers began growing them commercially. When people think of macadamia today, they think of Hawaii, as the best varieties were promoted as Hawaiian macadamias, even though they are now also grown in parts of Africa, tropical America, and Australia.
Besides macadamias, let’s look at other nuts with potential. Cashews are a good fit for the home garden. The nut or seed develops at the bottom of the cashew fruit. It is easy to grow from seed and grows into a small tree with a round head. Cashew trees are related to mango trees and have irritating sap, so the seed must be handled with care when processing. The juicy fruit is edible fresh or can be processed into juice or even an alcoholic beverage.
At higher elevations, above 4,000 feet, pistachios and almonds may be grown, but are not readily available from local nurseries. However, they can be special ordered from California. Growing conditions that are cool and dry are best.
Back to the coconut palm, it is a great tree for the Hawaiian garden. The dwarf Samoan form is the best and available at some local nurseries. The tree begins to produce fruit young and can be easily harvested at ground level for years. Another advantage is that it is resistant to the deadly yellowing disease that has killed millions of trees in Florida and the Caribbean. These palms thrive below 1500 feet in elevation but cannot tolerate the long cool temperatures above that.
When was the last time you had pili nut cake, pili nut chunks, or pili nut cookies? Unless you’ve lived in the Philippines, you probably never have. How about tropical almond cookies? Again, we don’t see those here, but tropical almond cookies are popular in Haiti and other parts of the Caribbean. The tropical almond, or false kamani (taxonomically, Terminalia catappa) is native to the East Indies, but is now found throughout the coastal areas of the tropical Pacific.
Another delicious but rare nut is the Brazil nut from the Amazon region. Bertholletia excelsa is known to boost your immune system due to its antioxidants. Unfortunately, this tree is only found in a few private and botanical gardens. If you manage to find a tree, do not eat the nut. Let it sprout. By the way, if you have a tree or know where one is, please let me know.
One of the tastiest nuts you can find in the Philippines is the pili. The pili nut, Canarium ovatumis native to the Philippines and is the most important of about 10 species of nuts. The tree reaches a final height of about 60 feet. It can easily be kept lower by good pruning. Leaves are compound like the African tulip. Flowers are yellow, fragrant and form in terminal clusters. Male and female flowers are produced on separate trees, so two trees of opposite sexes are needed to produce nuts on the female tree.
The oblong greenish fruits are black when ripe and are nearly 2.5 to 3 inches long. The nut can be eaten raw or roasted and some consider it superior to the almond. The kernel is processed into a variety of products including plain roasted nuts, sugar-coated nuts, pudding, and pili nut butter. They are excellent in nut chocolates and are a source of good cooking oil. Resin can be tapped from the tree, as in the rubber tree. It is used in perfumes, glues, plastics, printing inks, paints, varnishes, and many other products.
The University of Hawaii College of Tropical Agriculture and Human Resources has spent years researching the production of pili and found that it grows very well at lower elevations. It is a beautiful tropical tree that needs protection from strong winds and irrigation when rainfall is less than 50 inches of well-distributed rain per year.
The limiting factor in growing pili trees is the availability of plants. Most trees in Hawaii and the Philippines are grown from seed. Grafting and grafting are difficult. Air layering has limited success. Since the University has a number of trees at the UH Experiment Station near Hilo, it is possible to obtain seeds by contacting our UHCTAR Agricultural Extension office there. Ask one of the Master Gardeners to assist you. In Hilo, the number is (808) 981-5199. Seeds are not always available, but can be obtained when in fruit.
Since the politics of 2024 are making a bit of a fool of us all, it’s a good time to do some soul-searching by planting some nuts in your garden!
Norman Bezona is a professor emeritus in the Department of Tropical Agriculture and Human Resources at the University of Hawaii.
