Should you prune your flowering shrubs, flowering shade trees, and evergreen privacy plants? Although doing so can render them “a cut above” those of your neighbors, proper timing and technique are essential, so that you don’t accidentally eliminate potential blooms instead.
For the best results, use bypass pruning shears--such as Felco Model 2— for branches no larger than 1/2 inch in diameter and bypass loppers—such as Corona ComfortGel Bypass Loppers— for those up to 1 1/2 inches across.
Ever-blooming roses continue to produce flowers intermittently all summer on new wood, shoots produced the same year as those blooms. Rose bushes of this type—including floribundas, grandifloras, hybrid teas, and miniatures, as well as most modern climbers and shrub roses—should be pruned in spring at about the time that forsythia flowers in your zone.
Once-blooming roses generally flower in early summer on old wood, shoots produced the previous year. Since these bushes—which include heirlooms such as albas, centifolias, damasks, gallicas, mosses, and ramblers—bloom only once per year, avoid pruning them in spring or you may cut off your potential buds for that year.
Vigorous old roses usually don’t require much shaping unless they have grown too “high and mighty,” in which case you can cut them down to size shortly after they have finished blooming. The (also heirloom) bourbons, hybrid perpetuals, and portlands bloom on both old and new wood, so you’ll probably want to wait until after their initial flush of flowers to prune them too.
For all roses, remove any deadwood first by cutting back each cane to where the pith at its center is greenish-white rather than brown. Floribundas, grandifloras, hybrid teas, and miniatures may require further reduction until they are only about one half to two-thirds the height they were the previous year. Though Knockout Roses don’t need much pruning, you may want to clip them back by that amount as well to keep them compact. Always finish your pruning of each cane with a slanting cut just above a live outward facing leaf bud.
Wait until modern climbers and shrub roses are three years old to remove about a third of the oldest and grayest of their canes each spring. Cut those all the way back to the ground.
The proper time to prune your hydrangeas also will depend on whether they bloom on old or new wood. Old wood varieties—such as the big-leaf and oak-leaf types—bloom early in the summer and generally have stopped doing so by midsummer. Prune those just after their flowers have begun to fade and before the beginning of August to give them plenty of time to produce new growth before winter. Remove any deadwood and about one third of the stems, picking out the weakest ones and cutting them back to the ground. New wood hydrangeas—including the panicle and smooth types—bloom later, from mid-summer to autumn. You can prune them in early spring, cutting the old stems back to heights between 1 and 2 feet, so that they will help support the new growth. Modern ever-blooming hydrangeas—such as ‘Endless Summer’—bloom on both old and new wood and generally don’t require pruning, except for the removal of shriveled flower clusters.
Crepe Myrtle Cuts
Crepe myrtles are too frequently subjected to a scalping that comes close to a decapitating. Avoid this mistake by keeping in mind that your myrtle is a tree, not a hedge plant.
Prune it in late winter or early spring before it leafs out, so you can clearly see its structure. This tree generally looks best with an odd number of trunks—preferably three or five—so you may want to remove extra ones.
Also, prune out any suckers at its base and all side branches at least a third of the way up the tree. In its canopy, remove shoots which are rubbing against each other, growing inward rather than outward, or are smaller in diameter than a pencil. Cut unwanted side growth back to the branch to which it is attached and an unwanted branch back to the trunk of the tree, leaving a small collar in both cases rather than cutting flush with the branch or trunk .
Prune evergreens in spring or in midsummer (before August), keeping in mind that many of them have a “dead zone” at their center where needles are no longer present. Don’t cut back that far, because no new growth can sprout from that area. If possible, confine your pruning to a light trimming on the outer surfaces to keep the growth bushy and compact.
For pines, you can pinch the new candles (long buds at the tips of the branches) back by half in mid to late spring, preferably using your fingers rather than shears to avoid cutting any needles which will remain on the tree. For arborvitae, false cypress, firs, junipers, and spruces, prune each tip you want to shorten back to a lateral bud or branch. You can do the same for hemlocks and yews, but they also will tolerate heavier pruning, so they are a good choice if you want to hedge your rose garden— or your bets!