There are nine species of macadamia of which seven come from Australia. However only two of these Australian macadamias are edible, Macadamia integrifolia and Macadamia tetraphylla, the rest being inedible or poisonous. The aborigines of Australia removed the poison from the toxic species by prolonged leaching in water.

The Macadamia is a member of the protea family, as is New Zealand native honeysuckle, Knightia excelsa, to which it bears a passing resemblance with its long leaves with their prickly saw tooth edging. It is an attractive densely branched small treegrowing about six to seven metres tall in average conditions. In spite of being native to Queensland, Australia, the edible macadamia is suitable for growing in milder regions. To do well macadamias need a warm and ideally frost-free sheltered position in a well drained soil. They are shallow rooting so may need some extra watering during times of drought. Like other surface rooting trees it is also best to apply mulch, which also conserves surface moisture, rather than digging to control weeds which can damge the feeding roots. The trees can be given a balanced fertiliser low in phosphates in early summer.

If you experience some frosts then you can still grow these tasty treats by covering young plants until they are established and can tolerate lighter frosts. It pays to note that macadamias do not like strong winds especially those laden with salt spray. Being shallow rooted, they are prone to wind throw.

Selected varieties of the trees are usually propogated by grafting, normally producing nuts from about their sixth or seventh year and can continue bearing for more than one hundred years. The white to pinkish, scented flowers are produced in long racemes from spring and early summer when they attract lots of honey bees and bumble bees which pollinate them. The nuts have a hard woody outer casing and are produced in loose bunches. These ripen over the summer and are mature enough to begin falling off the tree by autumn.

With a world-wide production of about 100,000 tonnes, macadamia nuts are one of the most expensive to buy and are often considered to be the best. Interestingly, they are the only native Australian food plant to be grown and exported  in any appreciable quantities. They are highly nutritious and contain the highest amount of beneficial fats of any nut. However they are one of the hardest to crack successfully without shattering the kernel; one of the screw type nut crackers especially designed for macadamias being the most successful.

Macadamia's rich creamy flavour makes them ideal for the production of many chocolate covered delights. We have also made the most delicious pesto using them with basil and parmesan cheese. They are also used in the pharmaceutial industry and they contain the highest rate of about 22 percent of Omega 7 palmitoleic acid, apparently a highly desirable ingredient in cosmetic skin care preparations.

Two interesting pieces of macadamia trivia from the internet: macadamias are toxic to dogs, making them weak and unable to stand within 12 hours of ingestion, but usually recovering after 48 hours. When chopped, macadamia nuts resemble crack cocaine in colour and are sometimes use to simulate the drugs by authorities in drug stings.

Article sourced from Fairfax Media 4 September 2008