Reconsidering shrub pruning
Recently I drove by two landscaped areas containing a dozen or so 10+ year old crepe myrtles. Over half of the plants were totally dead, victims of the extreme cold of last winter. Some of the others had sprouted from the base, but not from last year’s wood. All were severely pruned last fall. At our place over half the butterfly bushes that were cut back in fall totally bit the dust, while others that were left alone are growing normally, although some dead branches needed to be removed.
Master Gardeners and Extension agents have fielded many calls about dead and damaged shrubs this year, and a pattern seems to be developing that is causing us to reconsider when these plants should be pruned. We still recommend that flowering and evergreen shrubs not be pruned after August first, because new growth at the pruning cuts won’t have time to mature before the cold weather hits. And that could provide sites for insects or diseases to enter the plant.
But we also have said that pruning after the first hard freeze was ok, because the plant would be dormant and no new growth would occur. This may not be as safe as once thought. It appears that the survival rate was lower for shrubs that were pruned severely last fall, as if that extra wood on the plant provided some protection against sub-zero temperatures. So the current recommendation from the horticulture experts at N.C. State is to postpone pruning shrubs until late February or March, after the chance of extreme cold has passed.
For shrubs that flower on old wood like forsythia and rhododendrons, wait until they are done blooming before pruning. Pruning dead or diseased wood can be done at any time.
Jim Janke is an Extension Master Gardener volunteer in Haywood County. For more information call the Haywood County Extension Center at 456-3575. © 2014 NC State University.