Some questions seem to come in waves and the subject of pruning old, big rhododendrons is one that seems to be finding its way to Fletcher recently. I referred a couple of the callers to our "Cutbacks" publication before I realized that it is out of print and most agents currently employed have never seen that publication written in 1982 by Bir, Shelton, Bonaminio. Baker and Jones. It was entitled "Growing Native Ornamentals from Cutbacks in Western North Carolina."

So, on the subject of pruning back native seedling grown rhododendrons (which includes all of the wild plants on properties where homes have been built in the mountains), the best time to prune based on my observation and advice offered by experienced mountain landscapers as well as growers of "cutbacks" is late winter. In fact, they suggest doing the pruning "when the sap is down." That translated in our 1982 publication to pruning back hard (to within a few inches of the ground on plants that might be 12 to 15 ft tall) any time a few weeks after the first killing frost in the fall until the last frost in the spring. That is the "best" time.

The worst time is during the spring flush of growth or immediately following the spring flush of growth as new foliage is starting to harden off. The rest of the year is generally thought of as the second best time.

When this type of pruning is done, the results are startling and often described as ugly. The plants do not recover rapidly and, sometimes for months or over a year, it may appear that the plant has been killed. Usually the plant comes back and has fully recovered within 4 or 5 years, flowering again within three.

Does the same hold true for mountain laurel (Kalmia latifolia)? Yes.

Does the same hold true for container grown or field grown hybrid evergreen rhododendrons and mountains laurels? Sometimes.

Lignotubers develop in native evergreen rhododendrons and mountain laurel. These lignotubers (burls) are at the soil line, slightly below or slightly above the soil line. They are full of adventitious buds which eventually develop, break and grow into new shoots. There are also many adventitious buds on the base of stems.

Cutting propagated hybrid evergreen rhododendrons and mountain laurels that are grown in containers or the field usually do not develop lignotubers. However, the base of stems on these plants also contain lots of adventitious buds and the plants generally respond like the wild species if they are not cut back so far that all the adventitious buds are removed. Therefore, when pruning overgrown old hybrids, leave a foot or more of stump above the soil surface.

In either situation, be patient. It takes a long time for these plants to recover from such radical surgery.

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North Carolina State University