How to Grow & Care for Macadamia Nut Trees

The Macadamia genus has four different species of macadamia trees, two of which are mostly used for nut production. Native to Australia, this sub-tropical evergreen tree has a very limited range in the continental United States.

While known for its delicious fruit, the tree is notoriously stingy when producing nuts, so unless you are prepared to plant multiple trees to cross-pollinate or take steps to ramp up production, the tree might be more suited as an ornamental or shade tree than a crop tree.

Macadamia Tree Care

No matter your tree's desired purpose, you will want to follow a certain set of guidelines to give your tree the best chance to thrive. Here is a brief list of key points to keep your macadamia tree happy and healthy:

• Provide your tree with full sun.
• Plant in regions with moist to wet conditions with at least 50 inches of rain annually.
• If looking to use it for nut production, choose a grafted plant to shorten the time to maturity.
• Amend your soil to reach a pH level of 5.5-6.5.
• Fertilize annually with low nitrogen, low phosphorus, and high potassium fertilizer once mature.

Light

When planting your macadamia tree, sun exposure is one of the biggest conditions to consider when choosing where to plant your tree.

If planted in a spot that receives too little sun, this already slow-growing tree will suffer and not produce a tremendous amount of foliage. Later, when mature, produce fewer flowers and less fruit. To ensure you get the best growth out of your tree, plant it in a location that gets full sun.

Soil

While the macadamia is somewhat adaptable, a few things will help guarantee success when growing this relatively easy-to-maintain tropical evergreen. Test the acidity of your soil will ensure that you can amend the soil and fix its pH to achieve the macadamia's desired pH of 5.5-6.5.

Once you know the soil's pH, look at the soil's moisture content, macadamia prefers wet to moist soil that is well draining. If the soil in the area you plan to plant is too moist, mix in plenty of perlite. Ultimately the ideal soil for your tree should be rich, moist, and well-draining.

Water

Macadamia trees are native to a region that receives at least 50 inches of rain annually, so the tree expects to get a good amount of water. This averages out to about 92 gallons of water during a hot week, which often occurs in the regions the macadamia grows.

Irrigation is especially important during initial planting when the tree establishes itself, usually over the first one or two growing seasons and when it produces fruit.

Tip

Since this tree requires a lot of water, it is best suited for greenhouses where the environment can be more carefully controlled. Growing a tree in a greenhouse will often require root pruning to turn it into a bonsai.

Temperature and Humidity

Being a native to Australia, there are very few areas in the United States where the macadamia tree will grow outdoors successfully. The macadamia can also grow well in California, Southern Texas, Florida, and the Gulf Coast.

It can thrive as long as the requirements of warm weather with a good amount of moisture are fulfilled. Macadamia trees are in hardy in USDA zones 9 and 11, but not all regions in these zones have high enough precipitation.

Hawaiian Nut?

Hawaii is one of the few locations in the United States where macadamia trees can grow outdoors easily. In fact, macadamia nuts are sometimes incorrectly called Hawaiian nuts.

Fertilizer

Annual fertilizing is only recommended once the tree reaches maturity. Most often, this occurs within seven to ten years after planting.

Fertilizing with low nitrogen, phosphorous, and high potassium formula is best. A 0-0-50 NPK formulation, such as sulfate of potash, is a good suggestion.

Pruning

Naturally macadamia trees will have a vase-shaped crown. This is perfect if you are using the tree ornamentally or for shade. If this is the case the only pruning needed will be maintenance pruning to remove dead, dying, and damaged branches annually.

If you plan on using the tree for fruit production then you will want to start to prune the tree into a shape that will allow it to get the best amount of sun and airflow for the most abundant fruit production. When pruning, use sharp, clean pruning shears.

In order to do this, step away from the tree and imagine a cone around it. Remove branches over the first few years to give your tree somewhat of a cone shape, remembering to never remove more than 1/3 of the tree's material within a single year.

Types of Macadamia Tree

There are four species of macadamia trees, countless hybrids between these four species, and a vast amount of commercially available cultivars and grafted selections.

• M. integrifolia: One of the two trees used in commercial production with sweet nuts, self-pollinating, and grows to about 50 feet.
• M. tetraphylla: One of the two trees used in commercial production with sweet nuts that grows to about 32 feet.
• M. ternifolia: A tree with a bitter nut on the vulnerable list that grows to a height of about 26 feet at a medium rate.
• M. jansenii: On the endangered list, it is critically endangered, with only 100 known trees in the wild.
  
  

Propagating Macadamia Trees

Propagating macadamia trees from cuttings is perfectly doable, it will not allow you to see your first crop for at least a decade. This also does not guarantee that the tree will produce abundant fruit or stay healthy enough on its rootstock to reach maturity.

Most macadamia trees used for crop production are grafted onto a cultivar selected for heartiness to serve as rootstock. In taking a cutting, you lose the heartiness of the original rootstock. If still inclined to propagate, the best method would be by air layering, though the process is advanced.

Common Problems with Macadamia Trees

Generally, macadamia trees are easy to care for, with most issues coming not from disease or pests but rather from placement and conditions. If you give your tree the proper conditions, it will usually be happy, but here are some things to look out for:

Deer and Rodents

When the trees mature, one of the biggest issues will be unwanted wildlife eating your crop. The easiest way to avoid this is to be mindful of ripe fruit and watch for any macadamias that fall to the ground that may attract unwanted wildlife.

Fungus

Often caused by wounds from weed whackers or improperly cleaned pruning tools. The most common signs will be cankers or dark lesions. Macadamia is most susceptible to Anthracnose and Phytophthora ramorum.

From: thespruce