Rhododendron yedoense var. poukhanense

Korean azalea is a woody, deciduous to semi-evergreen shrub in the Ericaceae (blueberry) family and native to central and southern Korea. This spreading shrub reaches a height of 3 to 6 feet and a width of 6 to 12 feet, maintaining its leaves in mild winters. It is the parent plant to many of the current hybrid evergreen azaleas. The genus name derives from the Greek words rhodo, which means rose, and dendron, meaning tree. Yedo, from the specific epithet yedoense, was the former city name of Tokyo, Japan.

Plant it in partial to full shade in moist, rich, well-drained soils. Good drainage is essential as wet feet can cause disease problems and root rot; however, the soil should not be allowed to dry out completely. A thick layer of organic mulch will help keep the soil moist and the temperature even for the best root growth. It will need protection from drying winter winds. 

It looks attractive planted in small groups in shrub borders, as an informal hedge, or planted along a foundation. Its showy fragrant flowers make it an excellent choice for specimen planting near a patio or walkway or in a pollinator or butterfly garden where the showy, pink- purple blooms will provide nectar for visiting butterflies and hummingbirds. 

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, though Korean azalea has shown better resistance to Phytophthora root rot. This plant is frequently damaged by deer but tolerates browsing by rabbits.

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.