The macadamia tree, native to the rainforests of Australia, is a broadleaf evergreen grown for both its ornamental qualities and its highly prized edible kernel. It maintains dense, dark green foliage throughout the year, making it a prominent feature in subtropical landscapes. To correctly identify this species, one must examine the visual characteristics of the tree’s form, leaves, bark, and reproductive structures.
Overall Tree Form and Dimensions
A mature macadamia tree typically presents as a medium to large specimen with an upright and spreading growth habit. These long-lived trees can reach heights between 30 and 60 feet, though commercial orchards often keep them pruned to manageable sizes. The canopy is generally dense, providing substantial shade, and often forms a rounded or somewhat pyramidal silhouette.
The trunk is usually straight, supporting the substantial spread of the canopy, and it may begin branching relatively low on the tree. In a cultivated setting, the tree’s form is often shaped for optimal nut production, resulting in a symmetrical and robust structure.
Distinctive Leaf and Bark Features
The foliage of the macadamia tree offers one of the most distinctive features for identification. The leaves are characteristically arranged in whorls, meaning three to six leaves radiate from a single point on the stem. This whorled arrangement is a key identification marker for the genus.
Individual leaves are large, shiny, and leathery, displaying a deep, glossy green color when mature. They are typically lanceolate or oblong in shape and can measure between four and twelve inches long. While the leaves of older trees are often smooth along the margins, younger or juvenile trees, especially of the Macadamia tetraphylla species, may display spiny or serrated edges. New growth flushes may appear a lighter green or even bronze before hardening into the dark, mature color.
The bark on a macadamia tree is generally gray or brown and varies in texture depending on the tree’s age. When young, the bark is relatively smooth, but it becomes rougher and develops minor fissures as it ages and the trunk thickens.
Appearance of Flowers and Developing Fruit
The macadamia tree produces distinctive inflorescences, which are long, slender, drooping clusters known as racemes. These racemes can be between 6 and 12 inches long and emerge from the leaf axils, sometimes giving the tree a draped appearance. Each raceme contains hundreds of tiny, individual flowers.
The flowers possess four petal-like sepals, ranging in color from creamy-white to pink or even a purplish hue, depending on the specific cultivar. They are known for having a pleasant, sweet fragrance and are important for attracting the insects necessary for pollination. The developing fruit begins as a small, green sphere that takes six to eight months to mature.
The macadamia nut is encased in a hard, green outer husk, which is botanically a pericarp. This husk is dull green and somewhat resembles a lime or a small, round avocado during development. As the fruit ripens, the husk darkens and splits along a single seam, revealing the familiar round, hard, woody shell inside. The shell, which is extremely tough and smooth or slightly rough depending on the species, encloses the edible kernel.