Swamp Oak Plant Care

Swamp Oak (Casuarina glauca) belongs to the Casuarinaceae family within the Casuarina genus. Swamp Oak is native to eastern Australia. Swamp Oak is also known as Blue She-oak, River Oak.

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

Leaf size: approximately 2 inches.

Water a young or newly planted Swamp 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.

Swamp Oak thrives in full sun.

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

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

Feed Swamp 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.

Swamp 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.

Swamp 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 Swamp 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.

Swamp 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.

Swamp 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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Swamp 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.

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