When should I start pruning shrubs?

When to begin pruning shrubs in Central Kansas is a common question for many home gardeners. Below are some general guidelines to consider, but keep in mind that weather patterns are a little different every year.

Shrub TypePreferred pruning timeNotes
If the shrub flowers before June 1stPrune just after flowering finishesShrubs that bloom in spring develop flower buds during the previous growing season on “old wood.” If pruned too early, you will remove the flower buds. Examples of some shrubs that fall in this category include lilac (Syringa spp.), forsythia, fothergilla, kerria, mockorange (Philadelphus coronarius), oakleaf hydrangea, viburnum, and weigela.

Old, neglected spring-flowering shrubs often require extensive pruning to rejuvenate the plants. The best time to rejuvenate large, overgrown shrubs is late winter or early spring (late February & March). The heavy pruning will reduce or eliminate the flower display for a few years but the health of the shrub will be improved.
If the shrub flowers after June 1stPrune in late winter or early spring (late February & March)Shrubs that bloom later in summer and fall tend to “bloom on new wood,” which means they set flower buds on the current season’s growth. These shrubs should be pruned in late winter or very early spring, before they leaf out. Examples: butterfly bush (Buddleia spp.), beautyberry (Callicarpa spp.), trumpet vine (Campsis radicans), buttonbush (Cephalanthus occidentalis), smooth hydrangea (Hydrangea arborescens), hydrangea paniculata, summer-blooming spirea (Spiraea x bumalda and S. japonica), rose of Sharon, and chaste-tree (Vitex spp.).
JunipersMarch through SeptemberJunipers and arborvitae can be pruned just about anytime from March through September. Avoid the hottest days of summer. There is a limit to how far back these plants can be pruned due to the dead zone. This is the area in the center of the plant where all the green foliage has dropped. Cutting back into this area will result in no re-growth and a permanent dead spot. Limit pruning to shorter tips or branches that will not leave holes showing dead wood. Hand pruning to retain the natural shape is often best.

YewsMarch through SeptemberYews can be treated similar to junipers. These are more forgiving as they will regenerate growth if cut back harshly into the dead zone. Although the recovery from such pruning may be slow and even take a couple of years to regrow- depending on the health of the plant.
Shrub pruning See this post for shrub pruning tips.
RosesSee belowGeneral tips: (1) remove all dead wood down to the crown or 1 inch into healthy green canes; (2) prune out all signs of canker; (3) remove all weak, spindly or deformed growth (rule of thumb is to remove anything smaller than the thickness of a pencil); (4) remove all canes growing toward the center of the plant; (5) remove all suckers down to the crown even if it means moving soil aside; and (6) finally, thin out remaining healthy canes to the desired shape and height. See more in this KSU publication.
Shrub RoseLate winter or early springSimple pruning: remove the dead wood and any evidence of cankers or disease (discolored or sunken-in stems) and you are set for the year.

If a shaping is preferred, cut all the canes back to about 15 to 18 inches. If possible cut the canes back to a large bud that is pointing outward from the bush. Old woody canes can be completely removed to help open up the plant and promote new growth. These old canes can be cut to the ground. A pruning saw may be required.
Hybrid tea, grandifloras, or floribuna rosesLate March through mid April or after danger of killing frostStart by removing any tissue that has been damaged by winter conditions. Make the pruning cut at least 1 inch below any black discoloration so that only live tissue remains. Shape the rose. Remove pencil size canes to the ground. These small shoots do not develop nice flower buds.

Leave four to seven of the strongest canes and cut them to between 12 and 18 inches long. It is recommended to make the cut just above a large bud that is pointed outward on the plant.