Rhododendron (PJM Group)

PJM rhododendrons are a group of hybrid, broadleaf evergreen shrubs in the Ericaceae (blueberry) family that were developed by Peter J. Mezitt and his son in the 1930s to be exceptionally winter hardy. The genus name derives from the Greek words rhodo, which means rose, and dendron, meaning tree.

Growing 3 to 6 feet tall and wide, these rhododendrons prefer partial shade and protection from strong winds. They grow well in moist, acidic soils but do not like wet feet. If you have clay soil, amend it with organic material and plant the root ball high in the soil to help with drainage issues. Avoid overwatering and over-fertilizing. Pruning, if desired, may be done after flowering.  This plant is resistant to browsing by rabbits.

As with all members of the genus, PJM rhododendrons are perfect as mass plantings in woodland or natural areas and specimens in pollinator gardens. Their green foliage acquires purple tones in winter, making them a wonderful addition to a winter garden. They also make a great informal hedge plant.  

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. Full sun can scorch the leaves, and the roots rot if soil does not drain well. 

While rhododendrons 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. 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.