Originating from southeastern Queensland in Australia, Macadamia nut trees are a fast growing and medium-sized tree. Their dark green foliage develops in pairs of three or four, with a rare solitary leaf. The flowers are off-white in color, with long spikes ranging from 5-10 inches long. The nuts ripen in the fall and are ensconced in a leathery two-valved encasement that is approximately 1 inch in diameter. The case holds one or two nuts that have a smooth and hard shell with a white kernel inside.
The leading growers of macadamia nuts are found in the United States and Hawaii. The nuts prefer stream banks and lush rain forests environments. There are many varieties to grow, each with its own unique taste. The trees, which grow from seeds, will take 8-12 years to grow a macadamia nut. The highest quality kernel contains at least 72 percent oil.
The location and soil type is essential when growing healthy macadamia nut trees. The trees require deep, well-drained soils with a pH of 5.0 to 6.5. According to the University of Hawaii, "the trees requires 60-120 inches of rainfall a year and can be grown from sea level to an elevation of 2500 feet." (See References 1) Macadamia nut trees grow best in full sun, with a few hours of shade each day and should be kept protected from high winds. The branches are small and the nuts are very heavy so any strong winds can greatly damage the tree and its harvest. Fertilize the tree around the sixth month of growth. Use a fertilizer with no more than 1 percent nitrogen.
Harvesting and Pruning
Macadamia nuts are harvested eight to nine months of the year from July to March, typically by hand, although mechanical machines are used for large-scale production. Nuts should be harvested every four weeks when the weather is moist and rainy and less frequent in dry weather.
Pruning is also a key to a successful plant but should not be done frequently so as to protect the growing nuts. Prune the tree so there is only one main stem with horizontal branches starting at two to three ft. above the ground and at intervals of about 1 1/2 ft. Any dead or decayed branches need to be removed and buried to prevent insects and mildew.