Smooth-Shell Macadamia Nut Tree (Macadamia integrifolia)

Smooth-shell macadamia (Macadamia integrifolia), also called Queensland nut, is a majestic, evergreen tree native to southeastern Queensland, Australia. A member of the Proteaceae family, it's the primary commercial species for the premium edible nut.

Description

Tree 30–50 feet tall with a spreading, dense canopy. Leaves are oblong, 6–12 inches long, in whorls of 3–4, leathery, glossy green with wavy margins (smooth, not spiny like M. tetraphylla). Flowers are small, white to pink, borne in long, slender racemes. Fruit is a hard, smooth, spherical shell (1 inch) enclosing a single, round, creamy-white kernel. Nuts drop when ripe.

Growing Conditions

• Zones: 9–11 (mature trees tolerate brief 24°F / -4°C).
• Light: Full sun.
• Soil: Deep, well-drained, slightly acidic (pH 5.5–6.5), rich in organic matter. Avoid heavy clay.
• Water: Regular moisture; not drought-tolerant. 60+ inches annual rainfall ideal.
• Temperature: Subtropical; frost damages flowers and young growth.

Care & Maintenance

Mulch heavily. Feed with balanced fertilizer 3×/year. Prune to open canopy and remove dead wood. Cross-pollination improves yield—plant 2+ cultivars. Harvest nuts from ground; husk and dry. Grafted trees bear in 3–5 years; seedlings 7–10 years.

Uses

Commercial nut orchards, edible landscapes, shade trees in subtropical regions. Nuts are high in monounsaturated fats, used roasted, in confections, oils.

Potential Issues

Root rot (Phytophthora) in wet soil. Macadamia felted coccid, nut borer, anthracnose. Requires specific climate—challenging outside subtropics.

A rewarding but demanding tree for the right climate—patience yields premium nuts.