Harvesting to processing guidelines
Macadamia Nut Grower Fact Sheet
The Macadamia nut is a native of Australia and is a member of the Proteaceae family, related to the NZ Rewarewa. New Zealand provides a special opportunity to grow a clean healthy quality product.
Today, total world macadamia production accounts for less than 2% of the world trade in nuts. New Zealand produces less then 1% of this.
Macadamias require temperate climates and areas that have low frost risk though, as mature trees they will withstand minus 6 degrees - in general, if tamarillos can be grown so can macadamias.
Orchards are found in coastal areas of Northland, Auckland, Taranaki, Coromandel, Bay of Plenty, East Cape and Hawkes Bay. Macadamias flourish best in soil rich in organic matter, but can tolerate a wide range of soils from clay to sandy loam.
Main requirements include free drainage, a good pH balance of 5 - 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 NZ. When choosing which varieties to plant you should consider the following:
- How warm is my site?
- How fertile?
- How windy?
- Do I want to hand pick or harvest from the ground?
- Is the terrain suited to mechanical harvesting?
- What stocking will I use (ie: trees/ha.)?
It is advised to always plant a mixture of varieties scattered evenly throughout the orchard in order to ensure adequate pollination. You may choose to talk to your local nut processor for advice. Some varieties crop better under certain conditions, and do well with the correct pollinators along side. Today in NZ most varieties are good croppers in their own right. The society can put you in touch with consultants and nurseries to help you with selection of suitable varieties.
Macadamias are best planted in the spring but can be planted at other times with extra care from drought, frost, etc. Some growers looking for early returns plant trees in rows as close as 5m apart, with 2.5m between trees within rows. This gives a stocking of 1000 trees/ha. Other growers plant as wide as 10m between rows, with 5m between trees within rows, giving a stocking of 200 trees/ha.
Set-up costs may be less with this spacing, but time to achieve a financial return is longer. Other factors to consider in spacing are access for machinery especially harvesting machinery, light penetration and access for insects to assist pollination.
Allow headroom at the end of rows for machinery access and turning. A northerly aspect is preferred and the use of shelterbelts needs to be planned to protect young trees from prevailing winds, this is frequently removed as the trees come into production.
Consider the availability of irrigation and drainage. Humping and hollowing may be required to ensure trees have an aerated soil during wet spells.
Carefully consider the mixture of varieties you will plant and intersperse them well. Planting varieties which all exhibit the same variety characteristics eases the handling of the post harvest crop.
The macadamia is a forgiving tree and is suitable for those with limited spare time, but they respond well when cared for. The health benefits of habitually eating macadamias augurs well for their continued demand.
Seasonal pruning for shape and light is typically done in winter. Though the tree can reach 10m high, timely pruning maintains trees to a more manageable height.
Weed & Pest Control
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. Livestock is not recommended in the first four or five years and never goats. Rats can be a problem so effective eradication programs are essential. Possums may also eat soft green nuts.
The Society is working to establish the best methods of controlling these pests, and the results of research are published to members as they become available.
Annual leaf and soil analysis, with appropriate response, assists in maintaining healthy trees. Boron and zinc in particular are generally low in NZ soils, and are applied as a liquid to the foliage.
Nuts are generally ready to harvest late May or early June, but can be later depending on the variety. Harvesting can go on until late November. Nuts are picked by hand or swept up mechanically from the orchard floor, 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 yr old tree can produce 8kgs of nut-in-shell (NIS), increasing annually for a further 15 years, with the approximate price of $3 / kg.
Many orchards not achieving above two tonnes per hectare are found to have basic problems. These problems include inadequate drainage, cool sites, poor cross-pollination, poor nutrition and crowded planting.
Husking & Drying
The object of husking and drying is to produce nuts that are crisp, light in colour and free from blemishes. Nuts should be husked as soon as possible after picking, within 24 hours is best.
The Society may be able to help you find someone to work in with nearby. Moisture must be reduced to 1.5% for processing this can be assisted by hanging in onion sacks for 8 - 12 weeks depending on the ambient temperature and humidity.
The dryer the nut the better the storage characteristics and eventually the better the payout received. The nut should be firm and crisp. A kernel that is soft and doughy when bitten indicates that further drying is necessary.
Most orchards sell their crop as nut in shell (NIS) to processing companies. Contact the society for a list of these.
Packaging to reduce exposure to light, moisture and oxygen enhances the final taste of the nuts, and increases the shelf life. The society has developed criteria to ensure the highest standards are maintained.
Marketing is not regarded as a responsibility of the NZMS and is left to individual processing companies.
Information on current initiatives might be obtained by contacting the society.
This document is free to be copied and distributed. The intent of this document is to provide a brief overview of the issues involved in planting a macadamia orchard. It is not intended as an authoritative publication and no responsibility is taken for the reliability of any of the information contained in it.