Rhododendrons in the PJM group were established to survive the tough winters in the Midwest and New England and are often recommended for shady spots. (Photo courtesy David Stang)
Rhododendron is a good option for partially-shaded areas but not all may thrive the way you want. With 1,200 species in the genus and more than 28,000 cultivars in the world, it’s important to select from the right group when trying to cover a moderately shady spot.
According to Steve Henning, a rhododendron enthusiast in Berks County, Pa., many cultivars enjoy living in light filtered by other foliage or part of a house.
“The presence of part shade helps the plants fight insect pests and disease,” Henning writes on his website, rhodyman.net. “For example, the natural predators of rhododendron and azalea lace bugs do not thrive in full sun. Root rot is much more prevalent on plants where the roots can’t be kept cool. Usually plants that are infected with lace bugs will do much better if moved to areas with more shade.”
But full shade isn’t the answer. The partial sun aids but set, and helps keep the plant compact and dense.
In fact, Henning adds, full shade and poor air circulation can be deadly for rhododendrons, killing new growth and “eating away at the plant branch by branch.”
Fortunately, rhododendron’s popularity over centuries has led to numerous hybrids that are hardy in cool settings and shade tolerant.
Hybrids in the “PJM” group, developed and named for Peter J. Mezzitt in the 1930s, were established to survive the tough winters in the Midwest and New England and are often recommended for shady spots. Some of the hybrids in that group are Black Satin, Desmit, Elite, Henry’s Red, Regal and Olga Mezzitt.
P.J.M. rhododendrons tend to be smaller, grow about 3 to 5 feet tall with rounded shape and dark green, leathery foliage. They’re also heavy bloomers and don’t set seed.
For a taller option, Catawba rhododendron is an evergreen growing to a height of 6 or 10 feet tall and a width of 5 to 8 feet. The oval-leafed foliage is dark green and leathery, putting a course texture in the landscape. Flowers range in color from lilac to rose with green or brown markings in the throat.
“This plant is very hardy,” Henning writes. “It is generally dense under ideal conditions, but becomes more open in dense shade.”
On the shorter side, Henning says Ramapo and Snow Lady grow to three feet tall or less. Ramapo tolerates sun and shade, is hardy to minus-25 degrees F and blooms in bright violet-pink flowers. Snow Lady produces an abundance of white flowers, has fuzzy leaves and hardy to 5 degrees F.
Azaleas are part of the rhododendron genus but most are poor bloomers in shaded spaces.
The Made in the Shade collection developed by Transplant Nursery in Georgia offers a short list of deciduous hybrids that do well with less light.
They are Camilla’s Blush, Lavender Girl, Lisa’s Gold, My Mary and Rosy Cheeks.
On the evergreen side, most azaleas do well in partial shade, Henning writes, but are the poorest typed of rhododendron when it comes to heavy shade.
“Most will grow in heavy shade but become leggy with weak growth and will produce few if any flower buds,” he says. “The group of evergreen azaleas that does best in shade is the R. obtusum series including the Kurume Azaleas. They require some shade and don’t seem to be too adversely affected by moderate shade.”
Kurume azaleas are hardy to Zone 7 and grow to a dense 18-to-30-inch bush with glossy leaves that are covered in flowers at blooming.
Hybrids in that group include Mother’s Day, Rosebud, Sherwood Orchid, Sylvester, Hino Crimson, Hahn’s Red and Blaauw’s Pink.
