Tree Rhododendron Plant Care

Tree Rhododendron (Rhododendron arboreum) belongs to the Ericaceae family within the Rhododendron genus. Tree Rhododendron is native to Bhutan, China, India, Myanmar, Nepal, Sri Lanka, Pakistan and Thailand. Tree Rhododendron is also known as Himalayan Rhododendron.

Tree Rhododendron displays an upright, spreading shrub growth habit, reaching up to 6 ft tall with a spread of approximately 6 ft. Tree Rhododendron produces showy clusters of large, colorful blooms in various shades.

Leaf size: approximately 6 inches.

Water a young or newly planted Tree Rhododendron every 7–14 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.

Tree Rhododendron thrives in partial shade to full sun.

Rhododendron arboreum tolerates temperatures of 40–70°F. Tree Rhododendron prefers humidity levels of 40–60%.

Well-draining, acidic soil with high organic matter content such as peat moss, pine bark, and perlite. Good drainage is essential for Tree Rhododendron to prevent waterlogging, which leads to root rot and fungal issues.

Feed Tree Rhododendron 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 partial shade to full sun and well-draining, acidic soil with high organic matter content such as peat moss, pine bark, and perlite. Avoid low spots where water collects after rain.

Tree Rhododendron is suited to USDA Zone 8a – 9b.

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.

Tree Rhododendron can spread to about 6 ft (1.8 m) and reach about 6 ft (2 m) tall. Space plants about 6 ft (1.8 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 Tree Rhododendron 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.

Tree Rhododendron is hardy down to USDA zone 8a, so once established it can stay outdoors through winter in that zone and warmer ones.

Water deeply in late autumn before the ground freezes, and spread a 5–8 cm (2–3 in) layer of mulch over the root zone, keeping it away from the trunk.

Young and container-grown trees need extra protection: roots in a pot freeze much more easily than roots in the ground.

Tree Rhododendron can be propagated through stem cuttings, layering, grafting. Similar propagation techniques also apply to southern indica azalea plant care, which shares the same genus.

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

Tree Rhododendron is susceptible to aphids, lace bugs, spider mites. 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.

Tree Rhododendron grows outdoors in USDA Zone 8a – 9b. It survives winters down to planting zone 8a. Tree Rhododendron is native to Bhutan, China, India, Myanmar, Nepal, Sri Lanka, Pakistan and Thailand.