Rhododendron 'Dr. A. Blok'

'Dr. A. Blok' rhododendron is a compact, evergreen shrub in the Ericaceae (blueberry) family that typically grows to a maximum height and width of 7 feet. The genus name derives from the Greek words rhodo, which means rose, and dendron, meaning tree. 

Plant this cultivar in a location with partial or light shade and organically rich, acidic soils that drain well. It will not tolerate dense clay. This shrub will require regular watering, and the roots may rot if the soil does not drain well. Plant the root ball high in the soil to help with drainage. Avoid overwatering and over-fertilizing. Prune rhododendrons and azaleas after they bloom to preserve the current season's bloom, and allow time for the plant to produce flower buds for next year's bloom.  Rhododendrons and azaleas set next year's flower buds by mid to late summer. 

This plant makes a great addition to a shady border, as a low hedge, or an accent plant. Use it as an understory shrub in a woodland garden or naturalized area, or in a pollinator garden where its showy, bright pink flowers will attract bees.

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 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.