Nothing can beautify the spring landscape quite like the rhododendron species. I am referring to both azaleas and rhododendrons. If you consider yourself a novice to these plants you might find it helpful to know, as someone else once said, all azaleas are rhododendrons but not all rhododendrons are azaleas.
The flowers of each truly border on the spectacular and there are so many varieties and hybrids that even the best collector usually comes away feeling humbled, yet longing for more to cure their insatiable appetite. There are several native species, too, such as the Rhododendron canescens, called Piedmont azalea, that is found from Pennsylvania to Texas in the west and Florida in the east, and offers beauty coupled with tantalizing fragrance.
Botanically speaking you'll find rhododendrons members of Ericaceae family, a large group of acid loving plants. Alkaline soil to this family is like Kryptonite to Superman. What you may find interesting is that other members of the family include Kalmia or mountain laurel and edibles like the cranberry and blueberry.
Rhododendrons are different from azaleas in that their leaves are large and leathery while azaleas are small and also slightly hairy. Rhododendron's flowers are usually larger, and are borne on trusses at the ends of branches.
Both rhododendrons and azaleas prefer a soil with a pH around 5.5. When you consider that pH 7 is neutral then it becomes apparent if you have soil close to 8 then you have your work cut out for you. To be perfectly honest most would be far happier growing what is native to the region than to attempt soil modification.
Your site selection is very important. Woodland settings where they receive filtered light, is perfect. In addition to being acidic the soil must be fertile, organic rich and very well-drained. To accomplish this, it is best to plant on raised beds so that when we do get heavy rains, the water drains freely. This is such a critical issue that many experts even suggest planting them high where the top one inch of the rootball is above the soil profile and loose organic material is added around it.
Azaleas and rhododendrons are very shallow-rooted plants. Since you are planting high and in loose soil, they are prone to drying out, especially those newly planted. Supplemental water will be needed. Mulch is essential to conserve moisture.
With regard to azaleas there are so many outstanding varieties it makes it hard to choose the best for your landscape. It is a good idea to spread your selections around using some from several different groups. For example, the Southern Indica group is the most popular. I love them and butterflies do, as well. These are large shrubs and are cold hardy to around 10 degrees on average. Popular varieties are Formosa, G.G. Gerbing, Judge Solomon, George Lindley Tabor and Pride of Mobile. The 10 degree range however will be clear indication to northern gardeners to look elsewhere.
Among the most cold-hardy groups of azaleas are Kurumes and Girard hybrids. The Gable hybrids and highly popular Glenn Dale hybrids of which there are some 400 should also be at the top of the list.
Then there are groups like the Robin Hill hybrids and Satsukis. These are known to be late bloomers. In fact Satsuki means fifth month in Japanese. If a late frost knocks out blooms of other selections, these most likely will still have a bloom in April to early May. Even if a late frost doesn't occur, you have spread your azalea bloom over a longer period.
Gardeners also look for rhododendrons with the same criteria which are cold and heat tolerance. Heat tolerance is the limiting factor for the Deep South. Just when I think it can't be done however, I'll find a gardener who has found his location to be just perfect. Without going into a treatise on varieties it's best to visit with your certified local nurseryman or local chapter of Amercian Rhododendron Society about which selections do best in your area. America (red), Roseum Elegans (lavender), Scintillation (lavender pink) Gomer Waterer (white) and Wheatley (vibrant pink) are a few however that have stood the test of time and often found over a wide region.
Spring is a great time to plant, why not visit your local garden center this weekend?
(Norman Winter is vice president for college advancement, Brewton Parker College, Mount Vernon, Ga., and author of the highly acclaimed "Tough-as-Nails Flowers for the South" and his release "Captivating Combinations Color and Style in the Garden". Contact him at nwinterbpc.edu.)
(c) 2010, McClatchy-Tribune Information Services.