Many shrubs, trees should be pruned in March
Q: Can I prune shrubs, trees and evergreens in March or should I wait until the weather gets better?
A: Pruning can promote new plant growth, control plant size, encourage flowering, remove diseased or dead limbs and help contain insect and disease problems.
Pruning of some shrubs, however, is best left until later in the season. Early blooming shrubs develop their flower buds during the summer and fall of the previous year. As a general rule, shrubs that flower before June 15 should be pruned immediately after flowering. Pruning these shrubs in winter or early spring will eliminate the flower buds and this season's flowers.
Generally, the shrubs won't die if pruned, they just don't flower. Spring blooming shrubs include lilac, mock orange, weigela, forsythia, arrowwood viburnum, St. Johnswort and red twig dogwood.
Shrubs that bloom after June 15 can be pruned in early spring, generally February and March. Don't be afraid to prune but know what you are doing! There is a general rule to NOT remove more than one-third of a tree or two-thirds of a shrub in any one year. There are two main types of cuts: thinning (remove entire branch) and heading (shorten the length). It is not recommended to leave "stubs."
There is also the rejuvenation method, which is the complete cutting of all stems down to 4- to 6-inch stubs. This method is used when multi-stemmed plants become too large with too many stems to justify saving any one- and two-year growth. The following shrubs respond well to rejuvenation pruning: Anthony Waterer spirea, abelia, honeysuckle, beauty bush, snowberry and privet. Actually, every four or five years, sacrificing the season's flowers and rejuvenating some spring bloomers such as red twig dogwood by cutting them to the ground is a good idea. They look so much better with redder stems and healthier branches.
Evergreens can be pruned lightly in winter to provide holiday decoration. However, the majority of pruning should be postponed until late winter, early spring or summer depending on the species. For arborvitae, wait until mid-March and early April. Junipers can be trimmed in April.
Yews are best pruned between late March and mid-June and can be pruned again in September. Pines such as Scotch, white or mugho, are best pruned in mid-to late June just as the candles have elongated. Spruce, including blue, can be done in early July.
Most deciduous trees should be pruned while they are dormant, especially oak and elm. Pruning wounds on oak and elms can attract borers and beetles that are carriers of disease such as Dutch elm disease and oak wilt. Winter also permits a good view of branch structure. Dormant pruning of maples and birches is also recommended because these species will often "bleed" if they are pruned in spring. Ideally, deciduous trees should be pruned in February or March once the severe cold weather has passed. Pruning paints or wound dressings are not recommended.
- Terri Passolt
• Provided by Master Gardeners through the Master Gardener Answer Desk, Friendship Park Conservatory, Des Plaines, and University of Illinois Extension, North Cook Branch Office, Arlington Heights. Call (847) 298-3502 on Wednesdays or email northcookmg@gmail.com. Visit web.extension.illinois.edu/mg.