Growing Rhododendrons in the South
This is a rhododendron in my back yard. Her name is 'Caroline.' Isn't she purty? Unfortunately, growing rhododendrons in the South can be quite a challenge, unless you follow Grumpy's expert advice.
But before we get to that, let me dispel some confusion you may have about rhododendrons. People talk about rhododendrons and azaleas as two different groups of plants, but in fact, all azaleas belong to the genus Rhododendron. Our native azaleas, also called wild honeysuckles, are upright, airy, deciduous shrubs, often with fragrant flowers. Their Asian counterparts, like 'Hershey's Red' and 'Formosa,' are dense and mounding, non-fragrant, with evergreen leaves from 1 to 2 inches long. They usually grow from 3 to 8 feet tall and wide.
For this story, rhododendrons refers to those plants with large, evergreen leaves up to 6 inches long. They get bigger than azaleas, 8 to 12 feet tall and wide (although I've seen our native Catawba rhododendrons towering 30 feet tall in the North Carolina mountains). Rhododendrons have much bigger flowers than azaleas, bloom later, and are open, not dense.
You with me so far? Good. Now here's how to grow rhododendrons in the South.
Keys to Not Killing Your Rhododendron 1. Choose heat-tolerant kinds. The world's most glorious rhododendrons grow in Seattle, Ireland, England, New Zealand, and other places in the Goldilocks zone where it's not too hot, not too cold, but just right. We don't live there. We need rhodies that tolerate long, hot summers, such as 'A. Bedford' (lavender-blue), 'Anah Krushke' (reddish-purple), 'Anna Rose Whitney' (deep pink), 'Belle Heller' (white), 'Caroline' (orchid-pink), 'Roseum Elegans' (lilac-pink), 'Cynthia' (rosy-crimson), 'Nova Zembla' (red), Southgate Series (various colors), and 'Vulcan' (brick-red). Rhododendron Society folks turn up their noses at such "common" types, but in Grumpy's never-humble opinion, a live common plant beats a dead special one.
2. Pay attention to the soil! Rhododendrons need moist, acid, loose, well-drained soil that contains a good bit of organic matter. This is why they're hard to grow here. Most Southerners have either acid, clay soil or alkaline, clay soil. Rhododendrons hate both, because clay drains slowly and roots rot. Rhododendrons also hate being dropped into a turkey frier, but I doubt that happens very often. Once burnt, twice shy.
3. Plant a little high. No, I don't mean you should be a little high. This ain't Colorado. Grumpy means you should plant your rhododendron so that the top of its root ball sticks about one inch above the soil surface. Then cover the exposed root ball with mulch. This improves drainage and aeration around the root ball. No weed required.
4. Provide light shade, especially in the afternoon. Plant rhododendrons in the dappled light beneath tall pines and hardwoods. Don't plant in deep shade or the plants won't bloom.