Rhododendrons are large broad leafed evergreens. The leaves are usually long, medium green in color with a finish more matte than glossy. The flowers are showstoppers – huge clusters of blooms ranging from pure white, yellow, pink and red to deep purple. They usually bloom here in May to early June. For more information of the the azalea subgeneras of rhododendrons, see this article.
Rhododendrons are usually large shrubs – at least six feet or more – so they require adequate room to grow. There are dwarf cultivars available. It is preferable to pick one of those for a smaller space rather than try to prune a larger one to fit. While some varieties will grow in full sun up North or in the mountains, here they must have only morning sun or high filtered shade. The root system is fine and shallow and does not take hold quickly. Rhododendrons, like azaleas, prefer moist, acid well drained soil with plenty of organic matter.
After you have located an appropriate site for your rhododendron, dig a wide shallow hole. Unless you have sandy, sharply draining soil, plant the root ball so that it is two or three inches above the level of the surrounding soil. Mix in plenty of aged ground up pine bark and compost; then mound the soil around the plant. If you have very heavy clay soil, consider creating a raised bed.
Water your rhododendron well when you plant it and again every three to four days for the first season. Rhododendrons are slow to root into the surrounding soil so be sure to water the root ball itself, not the surrounding soil. If the root ball dries out it is very hard to get moist again.
Things to Watch For
Root rot: Warm wet heavy soil encourages the growth of bacteria which can cause root rot. Should the plant wilt and not recover upon watering, check the soil to see if it is staying too wet.
Weeds: Rhododendrons are very shallow rooted so be careful when weeding not to disturb them. Don’t use a hoe or spade. Mulch with pine bark or pine straw to discourage weeds and raise the acidity of the soil.
Insects: Rhododendrons are relatively pest free!
There are several selections of Rhododendron that do well with the heat, humidity and high night time temperatures of the Piedmont.
Roseum Elegans: Purple Flowers; 6 to 8 feet tall and wide
Chinoides: White flower with yellow eye; 4 feet tall by 6 feet wide
Catawbiense: Pink to light purple flower; 8 to 10 feet tall and wide
Scintillation: Pink; 4 by 4 feet