Rhododendron planting & care

Updated April 17, 2017

The University of Missouri Extension Service calls the rhododendron a shrub "for all seasons." These shrubs, with their deep-green, glossy foliage, add a nice splash of colour to a spring garden with their copious blossoms. The term rhododendron refers to both rhododendrons and azaleas and, once planted, they are easy to maintain as a solitary centrepiece plant or clustered along the edge of the garden.

What is a Rhododendron?

A rhododendron is an evergreen flowering bush. Some varieties of rhododendron may reach 80 feet, though most varieties grow to 5-12 feet tall. It blooms in spring with large clusters of flowers in red, lavender, purple, white and pink. Throughout the year, its leaves have a leathery feel and attractive dark green colour. Some varieties of azaleas are deciduous, adding yet more fall colour to the garden before winter sets in.

Selecting a Location

Rhododendrons grow best in humid climates with acidic soil. Soil with a pH between 5 and 5.5 is best. They do not do well in direct sun. Choose a location with either early morning sun or filtered sun throughout the day. Do not place rhododendrons in deep shade or areas of sustained winds. Choose a rhododendron that reaches a maximum size for the area it is to be placed. If you want a shrub that will grow to about 5 feet tall, choose a variety near that size that will require only light pruning, rather than a larger variety that will need heavier pruning.

Planting Rhododendrons

Planting rhododendrons is done in early spring or fall. Dig a hole in well-drained soil that is wider, but only as deep, as the rhododendron root ball. Rhododendrons have fine, shallow roots that do not grow rapidly, so try to keep as much of the root ball as possible when planting. Once planted, trim the foliage to promote root growth. After planting, The American Rhododendron Society recommends watering at least weekly for the first year. Place a hose at the base of the plant and allow the water to drip for several hours. Keep the plant heavily mulched to retain moisture and reduce temperature extremes. The Gardner's Network suggests a mulch of pine needles, as they are acidic and make the soil more acidic, which is beneficial to the rhododendron.

Pruning Rhododendrons

Rhododendrons should be pruned as soon after blooming as possible. Rhododendrons bloom form on the tips of the stems, so pruning too late will reduce the number of blooms the following year. Prune the flower clusters after blooming and trim the long branches to retain a compact shape. If diseased or dead branches are found, they may be removed at any time of the year.

Rhododendron Propagation

Some rhododendrons are propagated from seeds, but most propagation is done by cuttings. Softwood cuttings can be taken in August or September. Take a cutting that is 3 or 4 inches long, and remove the lower leaves. Place the cuttings into a moist mixture of sand and peat moss until roots are formed. Then place the rhododendron cuttings into pots, and water well.

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