Water Gum Plant Care

Water Gum (Tristaniopsis polyandra) belongs to the Myrtaceae family within the Tristaniopsis genus. Water Gum is native to New Caledonia. Water Gum is also known as Kanooka.

Water Gum displays an upright, spreading tree growth habit, reaching up to 30 ft tall with a spread of approximately 20 ft. Water Gum produces small, white or cream-colored flowers in clusters.

Leaf size: approximately 4 inches.

Water a young or newly planted Water Gum every 7–10 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.

Water Gum thrives in full sun to partial shade.

Tristaniopsis polyandra tolerates temperatures of 50–80°F. Water Gum prefers humidity levels of 50–70%. A pebble tray or humidifier helps maintain adequate moisture around the plant.

Well-draining, acidic soil with added organic matter like compost or peat moss. Good drainage is essential for Water Gum to prevent waterlogging, which leads to root rot and fungal issues.

Feed Water Gum every 6 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 to partial shade and well-draining, acidic soil with added organic matter like compost or peat moss. Avoid low spots where water collects after rain.

Water Gum is suited to USDA Zone 12a.

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.

Water Gum can spread to about 20 ft (6.1 m) and reach about 30 ft (9 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 Water Gum 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.

Water Gum is frost-tender (hardy to USDA zone 12). In colder areas grow it in a container and move it to a bright, frost-free place before the first frost.

Water Gum can be propagated through seeds, semi-hardwood cuttings. Similar propagation techniques also apply to hill water gum plant care, which shares the same genus.

See all plants toxic to cats and plants toxic to dogs.

Water Gum is susceptible to aphids, scale insects, leaf-eating caterpillars. 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.

Water Gum grows outdoors in USDA Zone 12a. It survives winters down to planting zone 12a. Water Gum is native to New Caledonia. In cooler regions, grow Water Gum as a houseplant or bring it indoors before the first frost.