Directorate
Communication

 

 

Cultivation of macadamias

Macadamias can be produced successfully in areas where avocados, papayas, mangoes and bananas do well.

The trees flower during spring from August to September. The further development of the fruit lasts 31 weeks.

Select high-quality nursery trees by inspecting the:

Plant container and roots

The size of the container is very important. If the container is too small, the tree becomes pot-bound and the taproot might be distorted. The tree may appear healthy in the nursery, but has little chance of reaching its full potential in the orchard. The weakened root system cannot provide the growing tree with sufficient water and nutrients. 

 

                    

        Strangled           Twist           Crank handle

 

        Pot-bound         Spiral          Well developed           

 

Distorted root systems

Climatic and soil requirements

Soil

Most soil types are suitable for the production of macadamias, provided they are well drained and have no restrictive layers in the top 1 m of the soil. Poorly-drained clay soils are not suitable.

Temperature

The ideal temperature for macadamias is between 16 and 25 °C. Although the trees can survive when temperatures drop below 3 °C, they should not be regarded as frost resistant.

Height above sea level

Height above sea level influences nut quality and production. Production declines dramatically above 600 m. Above 640 m growth is slower and trees take longer to produce.

Cultivars suitable in areas between 600 and 640 m above sea level are Mauka, Kau and Keaau.

Cultivars recommended nearer to the coast, 90 to 300 m above sea level, are Purvis, Makai and Keaau.

Cultivars

The cultivars recommended are: Keaau, Kakea, Kau, Purvis, Pahala, Mauka and Makai. They are regarded as superior to Nelmak 1 and Nelmak 2 for commercial processing and marketing. Their oil content is usually higher than 73 % and the sugar content is low enough to ensure an even, cream colour after the nuts have been baked. Under ideal circumstances the crack-out percentage will be higher than 40 %.

Soil preparation

Planting distances

As soon as the competition for light becomes too great, production will decrease.

To allow for tractors to move between the trees, the hedgerow planting system is used. With this system:

Tree shape of some macadamia trees
Cultivar Tree shape

Keauhou

Kakea

Keaau

Ikaika

Kau

Mauka

Makai

Spreading (umbrella)

Spreading (broad)

Upright (broad-upright)

Spreading (broad-upright)

Upright (upright)

Upright (broad-upright)

Spreading (umbrella)

Umbrella     Broad     Broad-upright

Pyramidal     Columnar

Various tree shapes

Intercropping

Other crops are sometimes cultivated between young macadamia trees. There are 3 main aspects to be considered before planting an intercrop.

Leaf analysis

Method of sampling

  • Select approximately 20 healthy trees, well distributed throughout the orchard, homogeneous in appearance, and representative of the orchard as a whole.
  • The selected trees must be clearly marked with, for instance, paint. In this way it is possible to take soil samples at the same places and leaf samples from the same tree every year.
  • Four leaves are taken from alternate sides of the trees giving a sample of 80 leaves.

The leaf that should be sampled

 

Fertilisation

Do not fertilise young, transplanted trees too soon. They must first become well established and start growing vigorously before any applications are made, preferably after at least 1 year.

Never apply fertilisers against the stem of young trees.

Fertiliser must be broadcast evenly from about 0,2 m from the stem to about 0,5 m outside the drip area of the tree.

Macadamia trees are very sensitive to root damage, therefore each fertiliser application must be followed by a light, controlled irrigation.

Fertilisers must not be worked into the soil.

When the trees are established and start growing, fertiliser must be applied regularly according to the table.

Quantity of fertiliser according to age (kg/tree/year)
Tree age (years)  LAN 28 %  Superphosphate  Potassium chloride

1

2

3-5

6-8

9-11

12-14

15+

0,2

0,4

0,6

1,0

1,5

2,0

3,75

0,2

0,2

0,3

0,5

0,75

1,0

1,35

0,1

0,3

0,5

0,5

0,75

1,0

1,25

 Zinc and boron sprays

Because most soils are naturally low in zinc, or the zinc is not available, this element must be applied every year. The following concentrations are recommended:

Many macadamia orchards are also low in boron and it is desirable to spray the trees every 2 years with 100 g borax or 75 g Solubor/100 l water right from the start.

Irrigation

Water stress often limits tree growth, as well as the set, growth and quality of macadamia nuts. It is important to know how much water to apply and when to apply it if it does not rain.

Water requirements

The approximate water requirements for macadamia trees (mm/month)

Tree age

Years

Month

  Aug. Sept. Oct.  Nov. Dec.  Jan.  Feb.  March  Apr.  May  Jun. Jul
5 16 20 24 27 29 29 24 21 14 9 9 9
10 46 57 69 77 81 81 67 59 38 26 26 26

Diseases and pests

Phytophthora root rot

This disease usually occurs as a result of mechanical damage causing injury. These areas usually become infected. Trees suffering some kind of stress such as drought conditions may also get the disease.

Nut borer

Nut borer is the common name for the larvae of 4 types of moths that can either burrow into the green husks of macadamia nuts or feed on the kernels. The damage can easily be recognised, but the moths are small and inconspicuous and seldom seen in an orchard.

Stinkbugs

Stinkbugs are the most important pest on macadamias in South Africa. Damage is caused by a stinkbug complex comprising at least 20 different types. The most important types are: two-spotted stinkbug, green vegetable stinkbug, coconut stinkbug, small green stinkbug, spotted stinkbug, yellow-edged stinkbug and yellow-spotted stinkbug.

Stinkbugs can cause crop losses of up to 80 %.

 

Damage

Most stinkbugs have 4 generations per year and each generation causes a different type of damage to the nuts.

  Control

Stinkbugs can be controlled chemically.

The shaking method is used to monitor the number of stinkbugs, especially the winter and spring generations when morning temperatures are low.

There are also other signs which may indicate the presence of stinkbugs:

Recommended guidelines

Harvesting, storage and processing

  • Macadamia nuts drop from trees when they are mature and are then collected from the ground.
  • The main crop is usually collected from March to July.
  • The area underneath the trees must be clear. Grass, old leaves, branches and other debris must be removed.
  • The nuts must be collected regularly, at least once a week.
  • Nuts remaining under the trees for too long lose quality and are susceptible to damage by mould, rats and other rodents.
  • During the main harvesting period the branches may be shaken to loosen the nuts. Never pick immature nuts.
Removal of husks

The green husks around the nuts must be removed as soon as possible after harvesting.

Drying

Storage

Shelling

Packaging

The fried or roasted nuts are packed in airtight bottles, tins or plastic containers for consignment and marketing.

 

For further information contact the
ARC-Institute for Tropical and Subtropical Crops
Private Bag X11208, Nelspruit 1200
Tel (013) 753 2071
Fax (013) 752 3854

 

This publication is also available on the website of the
National Department of Agriculture at:
www.nda.agric.za/publications

ISBN 1-86871-070-X

2000

Compiled by Directorate Communication,
National Department of Agriculture in cooperation with
ARC-Institute for Tropical and Subtropical Crops

Printed and published by National Department of Agriculture
and obtainable from Resource Centre, Directorate Communication,
Private Bag X144, Pretoria 0001, South Africa