Thyme-leaved Rhododendron Plant Care

Thyme-leaved Rhododendron (Rhododendron serpyllifolium) belongs to the Ericaceae family within the Rhododendron genus. Thyme-leaved Rhododendron is native to Honshu, Kyushu, and Shikoku, Japan.

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

Leaf size: approximately 6 inches.

Water a young or newly planted Thyme-leaved 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.

Thyme-leaved Rhododendron thrives in partial shade to full sun.

Rhododendron serpyllifolium tolerates temperatures of 40–70°F. Thyme-leaved 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 Thyme-leaved Rhododendron to prevent waterlogging, which leads to root rot and fungal issues.

Feed Thyme-leaved 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.

Thyme-leaved Rhododendron is suited to USDA Zone 11a.

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.

Thyme-leaved 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 Thyme-leaved 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.

Thyme-leaved Rhododendron is frost-tender (hardy to USDA zone 11). In colder areas grow it in a container and move it to a bright, frost-free place before the first frost.

Thyme-leaved 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.

Thyme-leaved 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.

Thyme-leaved Rhododendron grows outdoors in USDA Zone 11a. It survives winters down to planting zone 11a. Thyme-leaved Rhododendron is native to Honshu, Kyushu, and Shikoku, Japan. In cooler regions, grow Thyme-leaved Rhododendron as a houseplant or bring it indoors before the first frost.