Macadamia tetraphylla aka Macadamia Nut

Macadamia tetraphylla is an evergreen tree in the Proteaceae family. Common names include Queensland nut and rough shell macadamia. It comes from southeastern Queensland and northeastern New South Wales, Australia. It grows in or near rainforests, often beside rivers and creeks. These sites have rich soils with plenty of humus. Growers raise it for food in tropical and subtropical regions.

Growth is slow, with garden trees reaching about 33 feet [10 metres] tall and wide. Some trees reach 52 feet [16 metres], though most stay smaller. The long, narrow leaves have sharp points. The foliage stays on the tree throughout the year. Each flower has both male and female parts. Bees pollinate the flowers, and the tree is self-fertile. Its edible seeds sit inside very hard shells. This makes the kernels hard to extract.

This tree suits cool tropical and subtropical climates. In Australia, it can crop as far south as Sydney. Give it sun and moist soil with good drainage. It accepts sandy, loamy, and clay soils. It also tolerates mildly acid, neutral, and mildly alkaline conditions. Preferred daytime temperatures range from 14 to 28°C. Dormant trees may survive brief cold near −2°C. Yet temperatures around −1°C can badly harm new growth. Cold can also destroy the whole crop. PFAF lists USDA zones 9–12, but frost remains a clear risk.

The kernels can be eaten raw or cooked. They have a sweet taste and contain substantial amounts of oil. Ground kernels can enrich cereal flour with protein. Seeds can reach about 1.2 inches [3 centimetres] long. They may contain up to 72 percent oil. The oil has food uses, though the valuable kernels limit extraction. PFAF and Useful Tropical Plants report no known hazards. This does not establish safety for pets. PFAF lists no known medicinal uses.

The tree can form part of a food forest. A sunny woodland edge is another suggested garden setting. Its useful products extend beyond the edible crop. Seed oil goes into cosmetics, while shells provide fuel. Decomposed husks can become an ingredient in potting mixes. Green hulls contain tannins. Growers also use this species as rootstock for Macadamia integrifolia. PFAF records no weed potential. Fresh ripe seed offers a way to raise new plants.