While macadamia nuts originate and are cultivated in Australia, commercial production occurs primarily in Hawaii. Some countries in Latin America, Africa and Asia also grow macadamia nuts, while the trees are found in California and Florida for the continental United States. Native to Australia, macadamia trees are only found naturally in southern Queensland and northern New South Wales. The Hawaiian macadamia industry was grown from a variety from Australia that was repeatedly cloned.
Macadamia nuts are not picked from the tree, but are harvested when the nuts have fallen to the ground, a sign that they are fully ripe. A typical macadamia tree in an orchard can take seven years to start producing and will not reach full production until it is between 10 and 12 years old. Macadamias prefer fertile, well-drained soils, a rainfall of 1000 to 2000 mm (40 to 80 inches) and temperatures that do not fall below 10 °C (50 °F) (although once established, they can withstand light frosts), with an optimal temperature of 25 °C (80 °F). The macadamia tree is usually propagated by grafting and doesn't start producing commercial quantities of seeds until it's 7 to 10 years old, but once established, it can continue producing for more than 100 years.
That's why they've asked potential local nut observers to get involved in identifying old, wild macadamia nut trees that could contain this missing genetic diversity. This comparison revealed that all Hawaiian macadamias share distinctive markers with a small group of wild trees in Gympie, suggesting that all of the state's modern crops were probably cloned from a single Australian tree. However, the global supply of macadamia is expected to increase, thanks to countries such as China planting macadamia trees. In Hawaii, unpeeled macadamias began the season with their highest net agricultural value in history, 100 cents per pound, and ended the season with a new record of 110 cents per pound.
In the 1920s, the government offered a five-year tax exemption on land that was used solely for macadamia production, but most farmers weren't interested. In the 1860s, King Jacky, the elder Aboriginal member of the Logan River clan and the world's first “macadamia nut businessman”, was the first to market the nut to colonists. By comparison, wild Australian macadamias have a rich diversity despite their narrow subtropical forest habitat, according to the study. This means that the commercial macadamia tree has incredibly low genetic diversity, and the researchers hope that their findings will spur the discovery of wild trees and more “new genes”.
While there are ten species of macadamia trees, only 2 produce the expensive nuts, and it takes seven to 10 years for the trees to start producing nuts. Genetic diversity would improve crop productivity, increase disease resistance and allow macadamia to be grown in new locations, said one of the researchers, Dr. Craig Hardner. So how exactly did these Australian cultivars end up in Hawaii? For that, you can thank William Purvis, who planted the first macadamia tree on the Big Island in 1881.