Fertiliser for Macadamia Trees: Understanding Their Nutritional Needs

Macadamia trees (Macadamia integrifolia and Macadamia tetraphylla) are evergreen natives of Australia, known for producing nutrient-rich nuts that are both commercially valuable and popular in home gardens. To achieve healthy growth and consistent nut yields, understanding the nutritional needs of these trees is essential.

Macadamias grow best in warm, frost-free climates with well-drained, slightly acidic soil (pH 5.5–6.5). They are relatively slow-growing in early years but become highly productive when properly fertilised. Regular nutrition is critical as they have a long growth and fruiting cycle, demanding a steady supply of key nutrients.

Macadamia Tree Nutrient Requirements

Macadamia trees primarily need:

Nitrogen (N): Encourages vegetative growth and canopy development, especially in young trees.
Potassium (K): Supports nut fill, oil quality, and kernel size.
Calcium (Ca): Essential for shell development and root structure.
Magnesium (Mg): Critical for photosynthesis and overall plant health.
Boron and Zinc: Needed in small amounts for flowering and nut development.

Too much phosphorus should be avoided, as macadamias are sensitive to phosphorus toxicity. Fertilisers with a low phosphorus profile and high potassium and calcium content are ideal.

Soil Testing & Growth Stages

Soil testing every two to three years is recommended to track nutrient levels and adjust fertiliser plans accordingly. Leaf tissue analysis can also provide valuable insight into nutrient uptake and potential deficiencies.

Fertiliser needs vary by growth stage:

Young trees (0–3 years): Balanced NPK for root and foliage establishment.
Pre-bearing trees (4–6 years): Potassium and trace elements to support canopy and early nut set.
Mature trees: Higher potassium, calcium, and magnesium to support flowering and nut fill without encouraging excess vegetative growth.

A consistent fertilisation program tailored to tree age, climate, and soil condition helps ensure high productivity, tree resilience, and long-term orchard health.

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Best Fertiliser for Macadamia Trees in Australia: Choosing the Right Product

Selecting the best fertiliser for macadamia trees in Australia requires a focus on nutrient balance, formulation type, and timing of application. These factors work together to ensure healthy foliage, strong root systems, and high-quality nut production.

Application Timing and Frequency

Early spring: Use a balanced fertiliser like NPK 20-20-20 to support foliage and canopy flush.
Late spring to mid-summer: Transition to NPK 4-18-38 + CaMg to enhance flowering, nut fill, and oil content.
As needed: Apply Cal-Mag during or after flowering if deficiencies are visible.

Apply fertiliser around the tree’s drip line (not at the trunk) and water in well. In sandy or leaching-prone soils, more frequent light applications may be preferable.

Bulk Feeding Option

For large-scale growers or those with multiple trees, the 20L All Purpose NPK Liquid Plant Food provides an economical bulk solution that is ideal for frequent feeding or fertigation systems.

Avoid organic-only solutions for macadamias unless combined with a controlled synthetic program. Precision NPK ratios, trace minerals, and solubility make CompleteGrow’s chemical formulations more effective for sustained productivity and commercial-grade results.

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Using Urea and Foliar Fertilisation for Macadamia Trees

Foliar fertilisation is an effective technique for delivering nutrients directly through the leaves, especially when soil conditions limit uptake. Urea is commonly used in this method to provide nitrogen quickly and efficiently.

How to Apply Urea as a Foliar Fertiliser

Mix at 0.5–1.0% concentration (5–10g of urea per litre of water).
Apply during cooler parts of the day—early morning or late afternoon.
Use during key growth phases such as flowering and post-harvest recovery.
Do not apply more than 2–3 times per season to avoid excess nitrogen.

CompleteGrow’s Cal-Mag Hydroponic Nutrients Fertiliser can also be used as a foliar spray when additional calcium and magnesium are needed. This is particularly important during nut development and when deficiencies are seen in leaf tissue.

Benefits of Foliar Feeding Macadamia Trees

Faster correction of micronutrient deficiencies.
Supports flowering and nut set in critical stages.
Avoids nutrient tie-up in poor or waterlogged soils.

Foliar feeding should be used as a supplement to soil fertilisation—not a replacement. A combined program ensures long-term nutrient support while meeting short-term seasonal demands.

Frequently Asked Questions

What is the best fertiliser for macadamia trees?
CompleteGrow’s NPK 4-18-38 + Calcium & Magnesium is ideal for mature macadamia trees during flowering and nut set. For young trees, the NPK 20-20-20 formula supports early growth.
Can I use urea on macadamia trees?
Yes, in small diluted doses as a foliar spray. Limit use to a few times per season and avoid high-heat conditions.
Do I need Cal-Mag for my macadamias?
Calcium and magnesium are essential, especially during shell development. CompleteGrow’s Cal-Mag product is a reliable solution.
How often should I fertilise macadamia trees?
Every 4–6 weeks during the active growing season, with adjustments based on soil and tissue tests.
Can foliar feeding replace soil fertiliser?
No. It’s best used as a supplement for quick correction, not a primary source of nutrition.

Need help choosing the right fertiliser for your macadamias? Explore the full CompleteGrow range or speak with our team for expert seasonal advice.