How to Grow Macadamias

Macadamias: Macadamia integrifolia, M. tetraphylla

Macadamias will produce nuts from Queensland to Hobart, it all depends on what species or variety you plant. Their olive-green-crinkled leaves make for striking foliage, and the long strings of cream or pink flowers in spring make them a worthy addition to every garden.

Cultivation

Macadamias can be grown from seed, but take up to seven years to fruit, whereas grafted trees will bear in 3-4 years.

All macadamias do best in soils with high levels of organic matter, and as an understorey plant, they can tolerate some shade. They require more water than avocados and citrus, and relish blood and bone with some extra potash. Good drainage is essential, as is some wind protection, especially for M. integrifolia.

Macadamias are partially self-fertile, but crops will be increased if you plant two trees of differing varieties. Mulch your trees well to protect their root system from drying out, and to minimise weed competition. Pruning can be kept to a minimum. Macadamias flower on two, three and four-year-old wood, so too much pruning will reduce yields. In their formative years just train your tree to have wide branch angles. This is essential on windy sites, as limbs are prone to splitting off the trunk.

Harvesting

Autumn is the time to harvest the nuts, which generally just drop from the tree. Remove the hulls as soon as possible and dry the nut out of the sun. When it rattles it is dry enough to last in the shell for up to a year.

Varieties

M. integrifolia

This macadamia is best suited to Northern NSW and the tropics, and has the highest oil content, making it the first choice for roasting. The leaves are rounded, and the cream flowers develop into a dense cluster of smooth-shelled nuts. If you have the right conditions of abundant water, nutrition, and even, but not too hot air temperatures, M. integrifolia will produce more than one crop per year.

Varieties of this species include 'Hinde' that is frost-resistant, crops profusely, but is difficult to dehull, and 'Own Venture' that produces large nuts that fall from the tree when ripe.

M. tetraphylla

This is the macadamia for cooler regions and the further south it is planted, the more sun it needs. The pointy, crinkled leaves are decorated in spring by long, graceful, pink flowers. These turn into strings of easily hulled nuts with a thin pebbly shell. M. tetraphylla has a high sugar content and is considered the best flavoured nut for eating fresh. They can be roasted easily, but the sugars will caramelise, making them less aesthetic. 'Cate' is the industry standard in California, with easy to crack shells and 'Ellinbah', an Australian selection, has good quality, thin-shelled nuts.