We have been focusing our greediness on some juicy fruits for a while so it may be time to get some more consistent food here, something with proteins and lipids; we will therefore have a go today at a nice tropical nut, Macadamia integrifolia.
Most of the readers are probably familiar with walnuts (Juglans regia), hazelnuts (Corylus avellana), Southern folks will also know pecan nuts (Carya illinoensis) and people in Florida usually have access to coconuts (Cocos nucifera) but fewer know about the Queensland nut. I just gave a clue regarding the origin of the plant; it does originate from the Australian state of Queensland; more precisely from the rainforests of its southern part. The tree belongs to the Proteaceae family which comprises some 2000 species grouped in 80 different genuses, some have been grown for a long time due to their decorative effect (Banksia, Grevillea, Leucospermum, Protea and Stenocarpus to name just a few). They usually are evergreen coming from places in the Southern hemisphere (Australia and South Africa mostly) and thriving in temperate to subtropical and tropical climates, the giant protea (Protea cynaroides) being one of the national plants of South Africa. The Macadamia genus hosts nine different species out of which seven come from Australia, one from New-Caledonia (a French island off the South-East coast of Australia) and one from Indonesia. The genera name was given by the botanist Ferdinand von Mueller in honor of John Macadam, a Scottish born Australian scientist (so nothing to do with the homonym Macadam the inventor of the tar-covered pavement). The species name of integrifolia alludes to the fact that the leaves are entire, not dissected or compound. There is another species which produces edible nuts and grows naturally in the same area, Macadamia tetraphylla which is known as ‘rough-shell type' while M. ternicifolia is called ‘soft-shell type'. Both species tend to hybridize readily.
The tree may reach 15 meters (45 feet) high but the rather superficial root system makes it prone to falling in case of storms. The crown will also become rather massive. The leaves are rather tough and remind of holly though they are much bigger (up to 20 cm long ) and are born by whorls of three on the stems (hence the synonym M.ternifolia sometimes seen in former publications) they can be used to make nice wreaths and have a nice reddish-bronzy color in the juvenile stage. They are shiny green, darker on the upper face and depending on the strain may have spines along the margins. The flowers come in long pendulous inflorescences or racemes up to 30 cm long (one foot!) holding 100 to 300 individual hermaphrodite pink flowers. The fruit is a drupe covered by a shiny green husk containing one seed. The seed or edible part is protected by a very strong woody shell explicated in one of its vernacular name of ‘noix marteau' (hammer nut). This is probably the hardest of all nuts and ordinary nut-crackers will not survive more than a few rounds against this tough challenger! I personally use a good sized stone for the job; a hammer also comes in handy while the industry has developed specific machines which allow the shell to get cracked without smashing the seed flat in the process hence loosing a lot of its commercial value. Before gulping down this nice nut please remember that it has the highest commercial value on the world trade, so please consider a little respect! You may of course enjoy it right out of the shell but it can also be roasted and salted, covered in chocolate or used in various delicious recipes included some famous ice-creams. Now this fantastic nut can also be turned into oil to be used either as food or as cosmetic. On the edible side this oil is rather amazing; it contains 84% of monounsaturated fats, 3.5% of polyunsaturated and 12.5% of saturated ones and can be kept at room temperature without modification for one to two years. Besides it is full of anti-oxidants and also carries a good level of magnesium, manganese, thiamine, copper and iron! Its smoke point is at about 220°C (430°F) which makes it a very safe one for frying. The important content of squalenes and palmitoleic acid allows the oil to be widely used as component of many hair and skin protective products.
Back to earthy concerns now; how do we grow this one plant? The easiest way is by planting a seed, which is how I obtained the tree and nuts pictured in this article. Now of course serious growers will use seedlings only as rootstocks on which to graft selected varieties (there are many, mostly from Hawaii such as Kakea, Keaav, Makai...) using whip graft or side graft. A seedling will take six to seven years to start producing but will keep bearing more and more and once mature may very well fruit all year long, bearing at the same time flowers, green seeds and mature ones. Cuttings are rather easy but they tend to produce a root system which is too shallow hence making the trees sensitive to high winds and drought periods. A deep well drained soil with a good proportion of organic matter will suit them well, temperatures between 20°C and 25°C (68° to 77°F) are best, the grown tree can withstand -1°C (30°F) but will be killed at -6°C (21°C) and high temperatures (above 35°C/95°F) will deteriorate the plant. Water supplies should be regular; the minimum needed quantity is 1200mm per year. With most varieties the ripe nuts fall on the ground where you simply have to pick them, but some may require the use of a pole to shake them loose.
As said in the introductory paragraph this tree originates from Australia where the nuts have been enjoyed by aborigines for as long as they have been roaming the forests, large remains of cracked shells have been found by researchers to confirm this. Though Australia remains an important producer with a total surface of 7000 acres (roughly 28 322 000 square meters) and an extra 1000 acres more planted yearly, the number one producer is Hawaii where the first nut was introduced in 1882 and has done pretty well since then! Number three in South Africa with 6000 acres, Kenya follows with 4000 acres, then we have 2000 acres in Guatemala and 1700 for Brazil. In continental USA, Southern California is the place where Macadamia does best and where you will have a chance to taste it fresh from the tree.
I hope I did not manage to drive you completely nuts with all the details and figures and hope you will run to your closest fine food store and order a large bag of Macadamia nuts!