Macadamia, ProteaceaeVarieties: Macadamia tetraphylla and Macadamia integrifolia are two common commercial varieties but the proteaceae family also includes the native NZ Rewarewa (Knightia excelsa) and the Gevuina nut tree (Gevuina avellana, pronounced giv-wee-na)
Adult height: up to 20m
Lifespan: 70 years or more
Description: Tall slender tree, serrated edge to leaves, will start producing nuts at 2 years of
age, economic quantities at around 8 years of age.
Considered by many to be the most delicious nut in the world, the macadamia is now part of a small but thriving industry in New Zealand.
The macadamia nut is crisp and sweet, contains no cholesterol and with New Zealand’s ideal growing conditions can be grown both organically and with minimal intervention. The health benefits of eating macadamia nuts on a regular basis, augurs well for their continued demand.
The macadamia is a native of Australia and a member of the Proteaceae family, related to the native Rewarewa. Two species commonly grown for commercial use are Macadamia tetraphylla and Macadamia integrifolia, with other varieties available to suit different growing conditions. Currently most commercial orchards are based in coastal areas of Northland, Auckland, Taranaki, Coromandel, Bay of Plenty, East Cape and Hawkes Bay.
Macadamias require temperate climates and areas that have low frost risk although as mature trees they will withstand -6°C. Generally, if tamarillos can be grown so can macadamia trees.
They flourish best in soil rich in organic matter, but can tolerate a wide range of soils from heavy clay to sandy loam. Main requirements include free draining soil, a good pH balance of 5.0-6.5, irrigation when young and shelter from severe winds.
All macadamia trees grown for commercial purposes are grafted; there are approximately 600 different varieties not all of which are available in New Zealand.
When choosing which varieties to plant you
should consider the following:- How warm is your site?
- How fertile?
- How windy?
- Do you want to hand pick or harvest from the ground?
- Is the terrain suited to mechanical harvesting?
- How many trees will you be planting?
The macadamia is a forgiving tree and is suitable for those with limited spare time, but they respond well when cared for.
The green vegetable bug (Nezara viridula) is the most serious threat, piercing the nut, staining the kernel and rendering it valueless. Regular mowing is recommended to keep the grass and weeds under control. Sheep are used in some mature orchards but any kind of livestock is not recommended in the first 4-5 years - never run goats. Rats can be a problem so effective eradication programs are essential. Possums may also eat the soft green nuts.
Nuts are generally ready to harvest late May or early June, but can be later depending on the latitude. Picking can go on until late November. Nuts are picked by hand or mechanically depending on the variety of tree.
Top orchards in New Zealand have returned yields similar to the best overseas, i.e. 4-6 tonnes per hectare. In optimum conditions an 8 year old tree can produce 8kgs nut in shell, increasing annually for a further 15 years at a price of around $3/kg. Many orchards not achieving above two tonnes per hectare are found to have basic problems. These problems include cool sites, shady places, poor cross-pollination, poor nutrition and crowded planting.
For more information
NZ Macadamia Society
What is the Gevuina?
This member of the macadamia family is native to southern Chile and has been growing in NZ for almost 50 years.
Trials on the gevuina (pronounced giv-ween-a) as a commercial crop have been underway for several years now, with this particular member of the macadamia family enjoying cooler summers and lower temperatures all round, making it an attractive option for South Island growers.
The gevuina is very pretty as an ornamental tree but also produces nuts with a softer, thinner shell than its macadamia cousin.
More reading
Otago Crop Database
Nadene Hall
NZ Lifestyle Block magazine