River Oak Plant Care

River Oak (Casuarina cunninghamiana) belongs to the Casuarinaceae family within the Casuarina genus. River Oak is native to Australia and New Guinea. River Oak is also known as Creek Oak, River She-oak.

River Oak displays a tall, slender tree growth habit, reaching up to 50 ft tall with a spread of approximately 20 ft. River Oak produces small, inconspicuous flowers.

Leaf size: approximately 2 inches.

Water a young or newly planted River Oak every 14–21 days, soaking the whole root zone, until it is established — usually one to two growing seasons. Established trees mainly need water during long dry spells. In a container, water whenever the top few centimetres of soil are dry.

River Oak thrives in full sun.

Casuarina cunninghamiana tolerates temperatures of 60–90°F. River Oak prefers humidity levels of 40–70%.

Well-draining sandy soil with good aeration. Good drainage is essential for River Oak to prevent waterlogging, which leads to root rot and fungal issues.

Feed River Oak every 8 months during the growing season with a balanced, slow-release fertilizer at the rate on the label. Established trees in good soil often need little extra feeding, so let weak growth or pale foliage guide you.

Stop feeding by late summer so new growth can harden before winter.

The PlantoScan app can remind you when to water and when to fertilize each plant.

Choose a spot with full sun and well-draining sandy soil with good aeration. Avoid low spots where water collects after rain.

River Oak is suited to USDA Zone 13a.

Plant container-grown or balled-and-burlapped trees in spring or early autumn, setting the root flare at soil level, and water well after planting.

River Oak can spread to about 20 ft (6.1 m) and reach about 50 ft (15 m) tall. Space plants about 20 ft (6.1 m) apart so mature crowns don't crowd each other, and plant at least half that distance from buildings, fences and paths.

Planning a row or hedge? Try the tree spacing calculator.

Prune River Oak while it is dormant in late winter: first remove dead, damaged and crossing branches, then thin lightly for shape.

If it flowers in spring, prune right after flowering instead so you don't remove next year's buds. Never take off more than about a quarter of the tree in one year.

River Oak is frost-tender (hardy to USDA zone 13). In colder areas grow it in a container and move it to a bright, frost-free place before the first frost.

River Oak can be propagated through seeds, cuttings. Similar propagation techniques also apply to belah plant care, which shares the same genus.

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River Oak is susceptible to scale insects, borers. Inspect the foliage regularly, especially along leaf undersides and stems. Treat infestations promptly with insecticidal soap or neem oil to prevent spread.

Yellow leaves, brown tips or drooping? See common plant problems and how to fix them.

River Oak grows outdoors in USDA Zone 13a. It survives winters down to planting zone 13a. River Oak is native to Australia and New Guinea. In cooler regions, grow River Oak as a houseplant or bring it indoors before the first frost.