We asked Tricia and two other experts — Mark Weathington, director of the JC Raulston Arboretum at North Carolina State University, and Ray Head, president of the Southeastern Chapter of the American Rhododendron Society — to share their secrets to growing the iconic plant. Here’s what you need to know.
Tricia Ockinga Horticulturist and longtime rhododendron caretaker
Mark Weathington Director of the J.C. Raulston Arboretum at NC State University
Ray Head President of the Southeastern Chapter of the American Rhododendron Society
What is the No. 1 thing people should know about growing rhododendrons?
Tricia: If planted in the perfect place, they will thrive and be healthy and happy. Location is key, as well as proper watering and excellent drainage. Location, location, location! Think about where rhododendrons grow naturally — they are the undergrowth of our tree canopy. They like shade, dappled light, or morning sun. Never plant under an eave of a building, and plant so they’re protected from the wind. Some varieties might take more sun than others.
Mark: Rhododendrons cannot tolerate “wet feet,” which is when a plant is too low or in a spot that, after it rains, stays wet longer than the ground around it. They’re highly susceptible to some root-rot funguses, which are present naturally in our soil. So the fungus is there, but when the roots stay wet, they really have a problem.
Ray: Selecting a rhododendron that has a history of growing well in our climate is very important. As a group, the Dexter hybrids are beautiful and grow well.
So … how do you determine the perfect place to plant?
Tricia: I highly encourage taking soil samples before planting. North Carolina soil is naturally acidic. Rhododendrons like a pH of 5.0, and the pH has to be correct or close to correct in order for the plant to uptake nutrients. Much of the soil you dig into here is red clay, which is thick and holds a lot of water. You want to provide good drainage and airflow around the roots.
Mark: Don’t plant them at the bottom of a hill. On slopes, they’re great — somewhere they won’t keep water in their roots longer than they need to. Generally, we have acidic soils, which is what a rhododendron will want.
Ray: Acidic soil and good drainage are important, and high shade is beneficial.
What temperatures do rhododendrons like best?
Mark: It depends on the type that you’re growing. There are a lot of different ones. A lot of the early ones were bred for really cold temperatures, and they don’t love our heat. But more and more, you’re seeing rhododendrons bred for warmer climates. Do some research on the different varieties. If you give them some shade and some pretty well-drained soil, they’ll tolerate our temperatures.
Ray: High summer temperatures do not damage rhododendrons that grow well here — as long as they have sufficient moisture and high shade.
Let’s talk fertilizer. How high-maintenance are rhodies?
Tricia: Rhododendrons are pretty easy — they basically just sit and look pretty. They are fantastic massed together for a stunning show. If you’ve taken a walk through our woods, you know what I mean when you see a standing grove of them. If you have rhodies and it seems they’re not thriving, get soil samples before adding anything — never just start dumping fertilizer or nutrients on a plant; the result could be added damage leading to death!
What about pruning?
Tricia: Always remove dead or diseased branches. Follow the branch back to healthy wood and cut there. Also, it’s good to cut crisscrossing branches because they rub on each other and cause a wound — an entry for bugs or disease. Always sanitize pruners with rubbing alcohol between cuts; this prevents the spread of pathogens. Good airflow around and through the foliage makes for a happy plant!
Mark: I tend to be a “less is more” kind of person, so I’ll snip off a branch here and there if one branch is growing longer than others, or if something is looking ugly. I think one of the nice things about rhododendrons is that they tend to grow nice and even and become pretty plants without a whole lot of work on our part.
We want our rhodies, and we want them now. How do we make them grow faster?
Mark: Deadheading! The best thing you can do is remove the heads right after flowering, which prevents any seed from forming. Seeds take a lot of energy away from the plant, so if you remove that possibility, all that energy goes into the root and shoot growth and new flower development. Although, I will admit, I don’t deadhead my rhododendrons almost ever because I’m OK with them growing slower.
What do we do about weeds?
Tricia: Mulch reduces weeds considerably, maintains moisture, and keeps roots cool. I found that rhodies love pine needles; plus, I like the look. Be careful with hardwood mulch: It is very hot and can burn foliage. And be sure that when spreading mulch, you do not volcano it, please! Meaning, do not pile up mulch around the trunk or crown of a plant. It creates a lovely home for rodents and bugs that like to burrow, and a nice moist place around the trunk for pathogens, such as fungus.
Anything else we should know?
Tricia: When in doubt, hire a professional, and most certainly take full advantage of your local NC State Cooperative Extension Area agent, a valuable resource many people are not aware of! Their office is where you pick up soil sample kits.
Ray: Every spring, the American Rhododendron Society schedules tours, and they’re generally open to the public. Information about these tours can be found on our rhododendron chapter website. Feel free to email us questions!
Interviews with our experts were conducted by Tamiya Anderson, and have been condensed and lightly edited for clarity.
For more rhododendrons, don’t miss the amazing photos in our May issue!
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