Rhododendrons, Azaleas, and Native Azaleas look different from each other, but all are members of the Rhododendron genus. When I first started learning about plants, I found this terribly confusing. It made me think of the Newhart television show from the 1980’s: “Hi, I’m Larry. This is my brother Darryl. This is my other brother Daryl.”
There are more than 800 species in the Rhododendron (pronounced rho-doh-DEN-dron) genus. This huge family can be divided into three main types. Those known as Rhododendrons have large, leathery evergreen leaves and rounded bloom clusters about the size of a softball. To make a distinction, I’ll refer to these as “Rhodies.” Azaleas and Native Azaleas have smaller leaves and may be evergreen, semi-evergreen, or completely deciduous. Rhodie flowers have ten or more stamens; azaleas have five stamens in their funnel-shaped flowers. This week’s blog will focus exclusively on Rhodies. I’ll discuss Azaleas in the next blog.
Growing Rhodies in the hot, humid southeast can be a challenge. One gardener told me the secret to her success: “Plant it low and it won’t grow. Plant it high and it won’t die.” She planted her Rhodies by placing the rootball in a shallow depression, piling a 4-inch volcano of loose mulch on top, and watering abundantly. Rhodies need acid soil with a high humus content and moist but well-drained soil. They absorb water through their leaves as well as their roots, so they prefer overhead irrigation. Take care to soak the entire root zone. This is one shrub that does not perform well with soaker hoses or drip irrigation since the root zone is not uniformly dampened. Water in the morning so that leaves are dry before temperatures drop at day’s end. This will help to prevent fungal diseases.
Rhodies hate heavy clay soils, so amend the planting area with ground bark or peat moss or both. Partial shade or filtered sun is best. They have an affinity for the shade cast by tall pine trees. Too much sun bleaches and crisps the leaves; too much shade means few or no flowers. Avoid planting in windy areas. Fertilizer is rarely needed unless one wants to increase the growth rate. Any fertilizing should be done after blooms fade, using a product that is labeled “for acid-loving plants” like camellias, gardenias, hollies, and hydrangeas. Use particular care in removing weeds, since Rhodie roots are shallow and resent damage from cultivation. Limit pruning to the removal of spent flower heads. Such removal will prevent the plant from trying to form seeds and will result in a stronger plant. A gangly plant can be made more attractive by pinching the growing tips of limbs to force branching.
In the warm southeast, search for heat-tolerant cultivars like ‘English Roseum (light rose flowers), ‘Roseum Elegans’ (lavender pink flowers) and ‘Nova Zembla’ (red to dark pink flowers). These will range in height from six to ten feet at maturity, with an equal spread.
All parts of the plant are highly toxic to humans and pets.
I inherited this Rhodie with the property we bought, so I don’t know the variety. I love her freckles.
The leaves of this Rhodie are not diseased; they are covered with pollen shed by the oaks and pines overhead.