How to grow macadamia
Overview
Macadamia is a long-lived evergreen tree grown for its rich, buttery nuts. It requires warm, frost-free conditions and deep, well-drained soil to produce well. Patience is key: trees take 4–7 years to bear a significant crop.
Varieties
- Beaumont — A hybrid variety with high yield and good nut quality, popular in coastal NSW.
- H2 — The most widely planted commercial variety in Australia; produces large, high-quality nuts.
- A16 — A vigorous variety with excellent kernel recovery, suited to subtropical climates.
Soil Preparation
Macadamia prefers deep, well-drained loam with a pH of 5.5–6.5. If soil is heavy clay, plant on a mound. Add no lime; incorporate gypsum if drainage is poor. Avoid high-phosphorus fertilisers at planting.
Growing Guide
Plant macadamia in full sun with shelter from strong winds. Space trees 8–10 m apart. Dig a hole twice the width of the root ball and backfill with native soil; do not add compost. Water deeply twice a week for the first two summers. Mulch 10 cm deep but keep 20 cm clear of the trunk.
Sowing
Macadamia is rarely grown from seed for production; grafted trees are preferred. If sowing, plant fresh seed 2 cm deep in a mix of sand and compost. Germination takes 4–8 weeks. Transplant when 30 cm tall.
Care
Feed with a low-phosphorus fertiliser (e.g., 8-2-10) in early spring and late summer. Prune only to remove dead or crossing branches; maintain a single leader for the first 5 years. Reapply mulch annually after the wet season.
Companion Planting
Underplant with low-growing legumes like clover or comfrey to fix nitrogen and suppress weeds. Avoid planting near eucalypts or grevilleas, which may host scale insects that spread to macadamia.
Common Pests & Risks
Nut borer (Cryptophlebia) causes premature nut drop; monitor with pheromone traps. Scale insects can be controlled with horticultural oil in winter. Rats climb trees to eat nuts; use trunk guards or bait stations.
Harvesting
Harvest macadamia when nuts fall naturally to the ground, typically from late autumn. Collect weekly and remove the husk within 24 hours. Dry nuts in a single layer in a well-ventilated spot for 2–3 weeks before cracking.
In the Kitchen
Use raw macadamia in baking, salads, or as a snack. Roast at 150°C for 12 minutes to enhance flavour. Store shelled nuts in an airtight container in the fridge for up to 6 months.
Troubleshooting
Yellow leaves: often caused by iron deficiency in alkaline soil; apply iron chelate. Brown leaf edges: salt burn from over-fertilising; flush soil with water. Poor nut set: lack of pollinators; plant a second tree nearby. Dieback: root rot from wet feet; improve drainage. Sunburn on trunk: whitewash young trees in hot climates.