Rhodies And Azaleas: When Things Go Wrong

Rhododendrons and azaleas are an important part of many of our landscapes at this time of the year. In some cases they provide year-round screening if they are the evergreen types, and their blooms from April right through July can anchor a garden, be an outstanding specimen, or provide splashes of vivid color in one spot or several. Better yet, these plants are among the easiest to care for and maintain. That is, until there’s a problem.Deer seem to love the azaleas and can make an evergreen variety deciduous in a single night of winter browsing. An infestation of black vine weevils can make rhododendron foliage look like Swiss cheese, and their larvae can severely damage the shrub’s roots. But all in all, these plants are sturdy, hardy and incredibly reliable. You can find azalea plantings that have been maintained for half a century, and many areas on Long Island have rhody specimens that stand regal in their height and width, with some being 20 feet tall and just as wide.

But things go wrong. And when they do, it’s very hard to find help and information. If you want to check out this dilemma, try doing some reading on pruning either one of these shrubs. Most texts and articles simply tell us that they rarely, if ever, need pruning or care other than some disbudding of some varieties when they’ve finished flowering.

Do you remember how long and cold the winter of 2014 was? It got cold very early, and it snowed and snowed and snowed. Azaleas did fine if they were protected from the deer, and the rhodies, characteristically, just curled their leaves and shivered through it. But there was little food for the deer, and for the first time in my gardening experience I had extensive damage to some large and mature rhododendrons. In spite of the foliage having been sprayed with a reliable deer repellent, the need to feed was just so overwhelming that these guys had a feast.

I drove into the courtyard one January morning and couldn’t believe my eyes. We had planted dozens of large rhododendrons that were brought up from a Maryland estate in 2001. Once they were established they settled in and did fine. Planted in a semi-circle about 80 feet in diameter, the shrubs were about 8 feet tall and a wonderful sight in bloom or out. In two nights that all changed. A browsing group of deer and chewed and removed just about every leaf from the ground up to as high as they could reach. A once beautiful planting now looked ridiculously silly. What to do?

The winter of 2015 was even more vicious. Yes, there was plenty of snow, but it was the cold that was the record-setter. As it was one of the coldest winters ever recorded in New York, I would have expected the deer to have again feasted on the rhodies. Not a nibble. They made it through the winter just fine thank you. The azaleas, on the other hand, had a great deal of die-back, and we even lost a few plants. The azalea collection came from the same Maryland estate in 2001, and we’d occasionally lose a plant or two and there would be some winter die-back from time to time, but this year the damage was much more widespread.

In this case we had some clues, as we know it wasn’t from deer browse. Deer will browse on evergreen azaleas, but they have no reason to browse on the deciduous types until they leaf out … and many didn’t. But these azaleas, several hundred plants, are not in an irrigated area, and I suspect that some of the winter damage began during the summer of 2014, when it was very warm and dry. Exacerbate this stress with a long, deep, cold winter and you have the ingredients for failure among old and stressed plants. What to do?

I did a great deal of reading. I had a number of questions. Where and how do you prune these two related plants to stimulate new growth and restore their shape, and do you feed them in the process? As to the feeding part, there seemed to be two schools of thought. School A said you shouldn’t feed a plant that’s been stressed, as all you will do is further damage the root system that needs to regenerate. School B said feed them lightly to attempt to stimulate new growth while not burning the roots. I chose neither.

One of the things we’ve learned about root stimulation in the past 20 years is that, yes, fertilizers can and do cause added damage, but compost teas and biostimulants can make a world of difference. Compost teas have just a slight amount of organic nutrition that these shrubs can easily take up, but if these teas are properly brewed they also contain non-nutritive microbes that stimulate processes in the soil that encourage and enhance new root growth. This is the regime we’ve followed with both the rhodies and azaleas.

But what about the pruning? I’d learned from observing some rhodies that had been damaged by heavy snow what part of the answer was, and the deer gave me the other answer. Remember the winter of 2014, where the deer had denuded the rhodies from the ground up? If you panicked and pruned these plants in an effort to stimulate new growth, you may have done just that, and in five to seven years the plants would have recovered—maybe. But if you had done nothing, you would have been delighted to see all the foliage return the following year, with flowering resuming the second year after the browse. It remains to be seen, though, if the tops and bottoms of these shrubs will bloom the same year or in alternate years in the future. Could be a little weird if that happens.

The rhodies that had snow damage had their branches snapped by the heavy snow. These branches were pruned to clean the breaks and reduce some of the branches by a foot or more. This caused new stems to emerge as old dormant buds lower on the branches, and the plants broke out as new stems that are gradually rejuvenating but it’s a slow process. I’ve learned that rhodies do respond to pruning if you know where to prune, and prune just after any flowering has taken place, and that you need patience, years of patience, for recovery.

Pruning back the azaleas to promote new growth takes some common sense and a good eye. After flowering is finished, the plant will show you where new growth wants to take place with new “breaks” of foliage along the stems. The goal is to prune above these “breaks” to encourage the new growth and additional growth below that as well.

This is truly an art as well as a science. Now’s the time to do the work if it needs to be done, though. Check out this 1948 article (with pictures) on pruning rhododendrons: http://goo.gl/euLPys. It’s 67 years old, but timeless. Keep growing.