Q. We have several evergreens in our landscape that need pruning. I have been told we have junipers, yews and a row of taller arbor-vitae in the back. The junipers are spreading over the sidewalk, the yews are about 5 foot tall, and the arborvitae are about 8 foot in height. When can we prune them and how do we prune them? My husband wants to use electric shears to give them a haircut.
A.: Evergreen shrubs can be pruned anytime during the year, except for late summer and early fall.
Pruning shrubs in late summer can sometimes promote tender growth that might be zapped later by a hard frost or freeze. Each species has certain tricks when it comes to pruning. In general, it is a good idea never to remove more than a third of the shrub during any one season. Overpruning can sometimes overstress the plant. Some plants will not produce new growth on bare wood, such is the case with the juniper. You can make pruning cuts to reduce the junipers’ overall size, but don’t make cuts so that only bare wood remains. Make sure to make your cuts just above nodes, where there is foliage or a side branch directly below the cut. Avoid shearing the plant; this technique only results in a shrub with only a small amount of foliage on the outside of the shrub with nothing inside. Better to vary the depth of the cuts for a more natural look and a fuller plant. It’s more work, but your plant will thank you.
Vary your cuts on the yew also. Yew tissue can regenerate even if a cut is made to bare wood, but this should be done only in drastic cases where the shrub has been neglected or pruned improperly. Varying your cuts on the shrub at slightly different depths will result in a maintained appearance, but the shrub will be fuller and healthier with a more natural look. Think of your shrub like a factory. If the shrub only has a thin layer of foliage on the outside (fewer workers), then it may have difficulty making enough product (sugar and starch). It’s all about optimal production.
Remove the central leaders (the tallest part of the plant) on your arbor-vitae. You can do this by using a small pruning saw to make a cut just above a branch at the 6 to 7 foot height. Make the cut at an angle so water runs off the cut; this is a good tip to use with most pruning cuts. Trim back some of the side branches below the cut to shape things up. The shrubs will form a new central leader over time. Just remove this later on using the same technique. It is important to keep the arbor-vitae at a size that is manageable so the shrub doesn’t fall apart during a heavy snow or ice storm.
Instead of shearing, now is the time to style your evergreens for a fuller, healthier appearance.
The Plant Medic, written by Ricky Kemery, appears every other Saturday. Kemery retired as the extension educator for horticulture at the Allen County branch of the Purdue Extension Service.