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There’s more to a macadamia than a chocolate-coated, or salted, roasted nut. This plant might provide our best known and loved native food, but it’s also a beautiful shade tree for a medium-sized garden. Linda Ross shares the good oil on growing the king of the nuts in your own garden.
Macadamias grow particularly well in coastal gardens from Sydney to Queensland. As well as providing delicious nuts the tree is also ornamental, with interesting glossy green foliage and pretty sprays of small but abundant white flowers in spring.
In their favoured conditions of fertile soil, temperate climate and high rainfall, they will grow to heights of more than 15 metres, though they are smaller in the home garden. There are two species of macadamia that produce edible fruit: the smooth-shelled macadamia (Macadamia integrifolia); and the rough-shelled macadamia (M. tetraphylla). M. integrifolia, which is native to south-eastern Queensland, is the commercially preferred species. Fruiting varieties are normally grafted on M. tetraphylla rootstock, and for the home garden these grafted trees are the best choice.
Macadamias grow best in warm, frost-free areas and like a well-drained soil enriched with compost. Gardeners in cool climates who are keen to try growing a macadamia should protect the young tree from frost for the first few years: a hessian wrap around a few timber stakes will do. It takes six to seven years before the tree will start to produce nuts, but once it has matured it is likely to produce more than 50 kilos of nuts in their shells each year.
Macadamias are shallow-rooted, so need plenty of water, particularly during dry spells. Mulch to keep the roots cool and help prevent the soil drying out. Macadamias are members of the Proteaceae family, which includes waratahs, banksias and grevilleas. Like these other members of the family, they should only be fertilised with low-phosphorus feeds designed for native plants.
The nuts fall to the ground between March and September. Mature macadamia nut kernels are encased in hard woody shells surrounded by green-brown fibrous husks. As the nut dries over the next few weeks, the moisture content falls and the kernel shrinks away from the inside of the shell. This allows the shells to be cracked without damaging the kernel.
‘Dwarf Macadamia’ grows to about half normal size, but is a prodigious bearer of small-sized nuts. Ideal for pots or limited space.
‘Daddow’ is a vigorous, dense, spreading tree. It’s a great all-round performer in Queensland and NSW.
‘ A4’ is a precocious tree that can produce commercial yields in three years. It’s a medium-sized tree with an open canopy. It is susceptible to stress in high temperatures, and performs best in NSW and cooler regions.
Where to buy
Your local nursery