Royal Azalea Rhododendron schlippenbachii

Royal azalea is a woody, upright, rounded, deciduous shrub in the Ericaceae (blueberry) family.  It is native to China, Japan, and Korea. Growing 6 to 8 feet tall and wide, its showy, fragrant flowers appear in April to May. The genus name derives from the Greek words rhodo, which means rose, and dendron, meaning tree.

Although royal azalea will grow in full sun, it prefers dappled sun or high open shade and moist, well-drained, acidic, humus-rich soil. It does not tolerate dense clay, so if you have clay soil, amend with organic material. The roots may rot if soil does not drain well. Plant the root ball high in the soil to help with drainage issues. Pruning, if desired, may be done after flowering. 

Site this plant in a woodland or natural area. With its large size and showy flowers, it can be used as a dramatic specimen. Its flowers will also attract bees, butterflies, and other pollinators to a pollinator garden.

Insects, Diseases, and Other Plant Problems: Insect problems include aphids, borers, lace bugs, leafhoppers, mealybugs, mites, nematodes, scale, thrips, and whitefly. Diseases include canker, crown rot, root rot, leaf spot, rust, and powdery mildew. This plant tolerates browsing by rabbits but is frequently damaged by deer.

While these shrubs remain very popular for landscape use, many cultivars are susceptible to Phytophthora root rot—this leads to leaf loss, reduced vigor, branch dieback, and wilting. Implement good cultural practices first, such as improving drainage with organic matter or berms and avoiding overwatering or overfertilization. However, if you have a site with a history of this disease, consider planting one of the root rot-resistant alternative species listed in the left-hand sidebar. 

For suitable alternatives, see this video created by Charlotte Glen as part of the Plants, Pests, and Pathogens series.

VIDEO Created by Elizabeth Meyer for "Trees, Shrubs and Conifers" a plant identification course offered in partnership with Longwood Gardens.

More information on Rhododendron.