The macadamia nut tree, also known by the species name Macadamia integrifolia, originates in subtropical areas of Australia. When growing macadamia trees, a sub tropical climate with mild, wet winters and hot summers is required. The trees tolerate a range of soil conditions and grow well in sunny spots. This tree can be grown in the home garden in areas where winter temperatures rarely drop below freezing.
This species of tree grows 30 to 40 feet (about 9 to 12 meters) tall, with a spreading canopy. This deciduous tree produces rich, fatty seeds encased in a hard seed coat. The seeds, called macadamia nuts, are edible. Macadamia nuts have a creamy, slightly sweet taste and smooth texture and are considered an important commercial crop. Macadamia nuts ripen and fall continuously between fall and spring.
The ideal climate for growing macadamia trees is a mild, frost-free area with an average rainfall of 60 to 120 inches (about 150 to 300 cm) a year. The trees can be grown in areas with lower annual rainfall when irrigated. Macadamia nut trees can survive temperatures as low as 28°F (about -2°C), but may be damaged. The best growth is achieved at a temperature range between 68 and 77°F (about 20 to 25°C). Macadamia trees also prefer a location protected from wind.
Macadamia trees should be planted in areas that get full sun, though the trees will tolerate partial shade. They thrive in rocky or sandy soil, and will tolerate loamy soil and light clay as long as there is sufficient drainage. A soil pH range between 5.5 and 6.5 typically is ideal.
When planting a macadamia tree, a hole twice as wide and the same depth as the root ball should be dug in the planting area. Once removed from the nursery pot, the roots are placed in the hole with the base of the stem level with the natural soil line. It is important to plant macadamia trees at the same depth in the soil as they were in the nursery pot to prevent the trunk from rotting.
Propagation is done by grafting or seed. The seeds germinate reliably at 77°F (about 25°C) and start to produce nuts in eight to 12 years. Most commercial trees are propagated by grafting, as they'll start to produce within six to seven years after planting. A healthy macadamia tree produces 30 to 50 pounds of nuts a year for 40 to 50 years.