Yaku Rhododendron Rhododendron yakushimanum

Yaku rhododendron is a woody, evergreen shrub in the Ericaceae (blueberry) family and native to Japan. This compact plant grows slowly into a dense, rounded mound or dome 2 to 3 feet tall and wide, sometimes reaching a height and width of 9 feet. The genus name derives from the Greek words rhodo, which means rose, and dendron, meaning tree. The species name yakushimanum comes from the island of Yakushima where it is native.

Rhododendrons as a whole tend to do better in higher elevations with cooler temperatures. Plant in a location with partial to dappled shade and moist, acidic, well-drained, organically rich soils. It will suffer in hot southern summers and needs protection from afternoon sun though it tolerates sun better than other rhododendrons.

This shrub provides year-round interest with its thick, glossy and leathery, curled leaves with velvety brown hairs on the undersurface. New growth is covered in dense white hairs. Attractive dark-pink buds open to light-pink flowers that fade to white in mid-spring.   This plant tolerates browsing by rabbits.

Use this plant in a container on a patio or in the landscape at the back of a border as an understory, woody shrub in a woodland or natural area. It works well as a low hedge or planted in an Asian or pollinator garden where its flowers will attract bees and other pollinators. 

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 but tolerates browsing by rabbits. Early flowering makes it susceptible to spring freezes, especially if planted in sunny locations where leaves and flowers emerge early.

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.