Often you see rhododendrons described as shade-loving shrubs, but the ideal situation for most of them is partial shade. Some bloom poorly without sunlight each day. Too much afternoon sun can burn the leaves and spoil the blossoms. If you have full shade, seek out suitable varieties known to perform well in these conditions. Azaleas are included in the genus Rhododendron; some of these tolerate full shade.
More than 50 varieties of rhododendrons bloom between January and March. These winter bloomers naturally require less light to bloom. They are often underused because of weather unpredictability. Unusually cold weather or strong wind can destroy the flower buds, but certain practices help reduce damage. Plant winter-blooming shrubs near trees or structures that provide a windbreak. Christmas Cheer is a reliable winter-blooming rhododendron. The large trusses of pink flowers are welcome in January. Another nearly identical pink winter rhododendron is Rosamundi. Snow Lady is a white rhododendron with black stamens. It is under 3 feet tall, so it can be placed near buildings or walkways where is can be enjoyed in winter. These rhododendron varieties are cold hardy to U.S. Department of Agriculture plant hardiness zone 7.
Some rhododendrons are more adaptable to shade during any season. The P.J.M group of rhododendrons are some of the most reliable shade bloomers. Because they do not develop seeds, the energy goes directly toward producing flowers. Within this group are varieties with pink-to-lavender blooms such as Elite and Waltham. Henry's Red is the color its name implies. The true red flowers have even deeper red eyes that appear almost black. A choice white P.J.M rhododendron for shade is Molly Fordham. The petals are much sturdier than most white flowering shrubs, so they hold up well to spring rain. These are particularly cold-tolerant selections, hardy to USDA zone 5.
Royal azalea, or Azalea schlippenbachii, is a shade-loving deciduous shrub. An added benefit is their fragrant pink blossoms. Royal azaleas bloom in the spring. Ramapo is a common azalea or dwarf rhododendron often seen planted in masses. It provides lavender flowers as well as colorful fall foliage.
A newer group of azaleas is called the Maid in the Shade collection. Included are two lavender-pink varieties – Camellia's Blush and Lavender Girl – and two yellow varieties – My Mary and Lisa's Gold. A delicate variety, Nacoochee, boasts white flowers with pink edges. This group of azaleas range in hardiness from USDA zones 4 to 6.
- Meerkerk Rhododendron Gardens: Twelve Months of Flowering Rhododendrons
- The Master Gardeners: Caring for Rhododendrons
- Henning's Rhododendrons & Azaleas: Shade Tolerant Rhododendrons
- Great Plant Picks: Rhododendron 'Christmas Cheer'
- Oregon State University: Landscape Plants: Rhododendron 'Snow Lady'