Q. Which flowering shrubs should I prune now in the fall? I have some that bloom in spring, and some bloom in summer. A few have grown too big for their space, but I’d rather not dig them up. Can I prune them back even more?
A. First, let me say that most flowering shrubs, or woody ornamentals, are perfectly happy with little or no pruning. They are at their most beautiful when they are allowed to grow into their natural shape. Some, like forsythias, have an arching fountain shape that is stunning in bloom. Evergreen azaleas, on the other hand, have a spreading globe-like shape that if left to grow naturally, resemble a billowing cloud of blossoms when mature.
Both of these species bloom early in spring, and if pruning is needed at all, they must be pruned after blooming to give the plant time to grow new buds for the following spring. Winter pruning will remove the flower buds, so flowers will be scarce the first spring after a winter pruning. If your evergreen azaleas are outgrowing their space, and you cannot move them to a more suitable location, go ahead and do some thinning and shaping.
If you have a garden helper who is overly free with the hedge shears, don’t let them near your azaleas. This plant can take some hard cutting back, but trim the branches limb by limb, looking around and into the shrub to find extra-long or extra twiggy branches to cut back. Study the azaleas at botanical gardens or parks to see how the plant should naturally grow and use that to guide your pruning.
Native azaleas are deciduous, which means that they lose their leaves in the winter, and grow new leaves in the spring — in this case, the new leaves come in after the plant blooms in early spring. Native azaleas rarely, if ever, need pruning. They grow slowly enough that they rarely outgrow their space (if they have been planted with proper spacing). Again, these woody ornamentals should be pruned, if necessary, just after they have bloomed. This gives them time to develop next year’s flower buds during the summer and fall.
Forsythias, another early spring bloomer, are a breathtaking sight when left to their own devices to bloom in full sun, but more often than not, this mistreated plant is sheared into squares or globes or hedges that don’t bloom well, and really don’t look very nice. A good healthy specimen can actually take a fairly severe pruning, though, to give it a head start on improving its shape and allowing it to grow naturally. If your forsythia is already in pretty good shape, this plant is another that should be pruned lightly and shaped after blooming, so as not to sacrifice the next spring’s blooms.
The pruning needs of hydrangeas here in Georgia vary depending on the winter weather. I always leave mine alone until the new green growth emerges in spring. All that needs to be snipped off are the ends of the branches that were killed off by the cold.
Simply cut at an angle about a quarter-inch above the last green bud near the end of the branch. Some hydrangeas bloom on new wood, so you won’t lose flowers after a severe winter. The French or bigleaf hydrangeas bloom on old wood, which is last year’s growth, so a harsh winter can leave you with few flowers for a year. They set their bloom buds in late summer and early fall. Very cold winters will kill off those bloom buds on those old blue mopheads, and if you get tired of waiting for your hydrangeas to flower again, you could either plant a few new hydrangeas in front of the old or dig up the old plants and replace them. When shopping for new hydrangeas, look for species that bloom on new wood. These don’t mind the winter weather, because the bloom buds are formed the same year they open.
Rose bushes can be left as is over the winter, and cut back hard in early spring. The very popular Knock Out rose can be cut back a bit in summer after the first flush of blooms, to encourage another flowering display a few weeks later. Hybrid tea roses simply need the dead winter branches cut back to green wood in mid-spring. Tea roses don’t need to be cut back hard, as they are much slower growers than the Knock Out roses. Leave as much healthy growth as you can.
We have many species and hybrids of woody ornamental plants here in west Georgia, and your Carroll County UGA Extension office has brochures and resources to help you learn what the plants in your own yard need. Just stop by the office at 900 Newnan Road in Carrollton, or phone 770-836-8546 to speak to a Master Gardener Extension Volunteer. The first steps in pruning your flowering shrubs correctly are to learn what the natural growth pattern is of each species and to note when the plants bloom.