Time to Prune?
Late winter is the right time to prune summer blooming shrubs like Knockout roses but not spring bloomers such as azaleas and camellias. For most shrubs, the right time to prune depends on why you are pruning them and when they flower.
Pruning to Increase Flowers
Prune summer blooming shrubs now to increase their flower display and maintain healthy plants. These include butterfly bushes, beautyberry, Japanese spireas, and everblooming roses (Knock Out varieties, hybrid teas, floribundas, and grandifloras). Summer blooming shrubs produce flower buds on new growth. Pruning them now encourages lots of new growth to develop and can result in lots of flowers. To maintain a compact size, shrubs like butterfly bushes and beautyberry are pruned hard by cutting them down to around one foot above the ground each year.
Knock Out roses should similarly be cut back to around 18” each year to promote vigorous healthy growth. This type of drastic pruning is okay for vigorous summer blooming shrubs. Less vigorous shrubs can be pruned by cutting the ends of the branches back by several inches. If they are too dense, remove some of the stems completely by cutting them out at ground level. Other summer flowering shrubs that can be pruned in spring include peegee hydrangea, rose of sharon, abelia, summersweet (Clethra), and oleander, which can be cut back to near ground level to remove cold damaged foliage if needed.
Shrubs that flower in the spring formed their flower buds on the shoots and branches that grew last summer and fall. If these shrubs are pruned now, all of the flower buds will be cut off, eliminating this spring’s flowering. The time to prune spring bloomers like azaleas, flowering quince, yellow bells (Forsythia), and camellias, is immediately after they finish blooming. A general rule of thumb as to what is considered spring flowering is any shrub that blooms before Mother’s Day – though there are a few exceptions. Oakleaf and bigleaf hydrangea, Indian hawthorn, and Virginia sweetspire are all shrubs that bloom on old wood, but generally flower after Mother’s Day. Wait to prune these after they bloom.
Pruning Not Always the Answer
Not all shrubs need to be pruned on a regular basis. Many shrubs have a naturally compact habit, such as ‘Wheeler’s Dwarf’ pittosporum, dwarf yaupon, dwarf nandina, and ‘Carissa’ holly. The only pruning these shrubs need is to remove an occasional stray shoot or broken branch. Other shrubs, such as privet, wax myrtle, eleagnus, abelia, and loropetalum, grow large rapidly. When planted in small landscapes gardeners may try to keep these plants compact by repeatedly pruning them, but in the end it is just a matter of having the wrong plant in the wrong place. If you have a shrub that constantly needs to be pruned because it is too vigorous for the site, the best advice is to move it somewhere else and replace it with a shrub whose mature size fits the location.
Rejuvenating Overgrown Shrubs
Occasionally even an appropriately placed large shrub may need to be rejuvenated. Shrubs that have been neglected for years or have grown out of shape can be pruned back to within a few feet from the ground in late winter or early spring. When deciding how low to cut, remember that new growth generally occurs within six inches to a foot of the pruning cut. Do not be afraid to cut plants back dramatically to avoid the appearance of a shrub on stilts. Healthy shrubs will grow back from this type of pruning with amazing vigor, but not all shrubs can be pruned this way. Shrubs that respond well to this treatment include camellias, hollies, privet, Formosa azaleas, and wax myrtle. Rosemary and needled evergreens, such as junipers and arborvitae, should never be pruned this severely as they are unable to generate new growth buds on old wood.
Another method for dealing with large overgrown shrubs is to remove their lower branches back to the main trunk, shaping them into small, multi-stemmed trees. This type of pruning is very attractive for overgrown camellias, Japanese privet, wax myrtle, larger growing loropetalums, cleyera, and doublefile viburnum, and can be done at any time of the year.
Learn more about pruning from these great links:
- Pruning Ornamental Trees and Shrubs — a great 12 page guide from Purdue Extension: http://www.hort.purdue.edu/ext/HO-4.pdf
- Pruning Ornamental Shrubs — another great guide, this one from Missouri Extension: http://extension.missouri.edu/p/g6870
- Pruning Trees and Shrubs — guide from N.C. Cooperative Extension: https://www.ces.ncsu.edu/depts/hort/consumer/agpubs/ag-071.pdf
Use Extension Search to find research based information from Cooperative Extension systems across the U.S.
Visit your local Cooperative Extension office to learn more about gardening and landscape care. Go to https://www.ces.ncsu.edu/local-county-center/ to find your county Extension center or post your questions to be answered online via Extension’s ‘Ask an Expert’ widget.
Contact your local Cooperative Extension office to get expert advice from an Extension Master Gardener Volunteer:
- If you live in Pender County, call 910-259-1235
- In New Hanover County, call 910-798-7660
- In Brunswick County, call 910-253-2610
- In Onslow County, call 910-455-5873
- In Duplin County, call 910-296-2143
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