How to grow macadamia tetraphylla
Overview
Macadamia tetraphylla is an Australian native tree prized for its edible nuts and attractive foliage. It thrives in warm, frost-free climates and requires deep, well-drained soil. Unlike the more common Macadamia integrifolia, tetraphylla has rough-shelled nuts and can tolerate slightly cooler conditions.
Varieties
- Renown — A popular Macadamia tetraphylla cultivar with large, sweet nuts and a high crack-out percentage, well-suited to subtropical gardens.
- H2 — A vigorous tetraphylla selection known for good nut yield and flavour, widely grown in Australia's Queensland and northern NSW.
Soil Preparation
Prefers deep, well-drained soil with a slightly acidic pH (5.5–6.5). Sandy loam or volcanic soils are ideal; avoid heavy clay or waterlogged sites. Incorporate well-rotted compost before planting and consider raised beds if drainage is poor.
Growing Guide
Position in full sun with shelter from strong winds, especially when young. Plant in deep, well-drained soil (sandy loam or volcanic) with a pH of 5.5–6.5. Space trees 7–10 m apart. Water deeply and regularly during establishment; once established, water every 1–2 weeks during dry spells. Mulch to retain moisture but keep mulch away from the trunk to prevent rot.
Sowing
Soak seeds overnight and sow 2–3 cm deep in seed-raising mix in spring. Germination takes 4–8 weeks. However, grafted trees are far more reliable for consistent nut quality and are recommended for home gardens.
Care
Apply a low-phosphorus, balanced native fertiliser in spring and early summer. Prune in early winter to remove dead or crossing branches and to develop a clear trunk by gradually removing lower branches. Renew organic mulch annually in spring.
Companion Planting
Plant alongside other subtropical fruit trees such as avocado, citrus, and banana, which share similar water and sun requirements. Avoid using high-phosphorus fertilisers near macadamias, as they are phosphorus-sensitive. Also avoid eucalypts and other heavy feeders that compete for moisture.
Common Pests & Risks
Nut borer attacks developing nuts; remove and destroy infested nuts promptly. Scale insects can be controlled with horticultural oil. Rats climb trees to eat nuts; use tree guards or traps. Prevent root rot by ensuring excellent drainage and avoiding overwatering.
Harvesting
Harvest nuts when they fall naturally from the tree, typically from autumn to winter. Remove the husk and dry nuts in a single layer in a well-ventilated area for 2–3 weeks. The kernel is ready when it cracks cleanly and the interior is crisp.
In the Kitchen
Nuts can be eaten raw or roasted. Their rich, buttery flavour works well in baking, confectionery, and savoury dishes. Store unshelled nuts in a cool, dry place for up to a year; shelled nuts keep for several months in the fridge.
Troubleshooting
Yellow leaves: often iron deficiency in alkaline or dry soil; apply chelated iron and water deeply. Brown leaf edges: salt burn from over-fertilisation or saline water; flush soil with fresh water. Poor nut set: lack of pollination or excessive rain at flowering; plant multiple trees for cross-pollination. Root rot: caused by poor drainage; improve drainage and reduce watering. Scale on leaves: wipe off or treat with horticultural oil.