Rhododendron viscosum Plant Care

Rhododendron viscosum (Azalea viscosa) belongs to the Ericaceae family within the Azalea genus. Rhododendron viscosum is native to the eastern United States. Rhododendron viscosum is also known as Swamp Azalea, Swamp Honeysuckle, Clammy Azalea.

Rhododendron viscosum displays a compact, mounding shrub growth habit, reaching up to 5 ft tall with a spread of approximately 5 ft. Rhododendron viscosum produces showy, colorful blooms in various shades of pink, red, white, or purple.

Leaf size: approximately 2 inches.

Water a young or newly planted Rhododendron viscosum every 4–7 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.

Rhododendron viscosum thrives in filtered sunlight or partial shade. Avoid placing Rhododendron viscosum in direct, harsh sunlight for extended periods, as this can scorch the foliage.

Azalea viscosa tolerates temperatures of 45–75°F. Rhododendron viscosum prefers humidity levels of 40–60%.

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

Feed Rhododendron viscosum 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 filtered sunlight or partial shade and well-draining acidic soil with high organic matter content, such as peat moss or pine bark. Avoid low spots where water collects after rain.

Rhododendron viscosum is suited to USDA Zone 11b.

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.

Rhododendron viscosum can spread to about 5 ft (1.5 m) and reach about 5 ft (2 m) tall. Space plants about 5 ft (1.5 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 Rhododendron viscosum 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.

Rhododendron viscosum 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.

Rhododendron viscosum can be propagated through softwood cuttings, layering, seeds.

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

Rhododendron viscosum is susceptible to spider mites, lace bugs, 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.

Rhododendron viscosum grows outdoors in USDA Zone 11b. It survives winters down to planting zone 11b. Rhododendron viscosum is native to the eastern United States. In cooler regions, grow Rhododendron viscosum as a houseplant or bring it indoors before the first frost.