Many things anytime the tree branches grow long enough to cut, then it maybe is time to prune. But do you know that there’s an optimal time of pruning? Pruning at the best time of the year promotes the best for your tree’s health.
So when is the best time to prune in Minnesota? The answer is in the late dormant season which is later weeks of winter to early weeks of spring. This is the best time to prune to avoid diseases and other problems. Pruning in late winter, just before spring growth starts, leaves fresh wounds exposed for only a short length of time before new growth begins the wound sealing process. Another advantage of dormant pruning is that it is easier to make pruning decisions without leaves obscuring plant branch structure. [source]
Pruning at the proper time can avoid certain disease and physiological problems:
- OAK WILT DISEASE – DO NOT prune oaks from April to October to avoid oak wilt disease. If oaks are wounded or must be pruned during these months, apply wound dressing or latex paint to mask the odor of freshly cut wood so the beetles that spread oak wilt will not be attracted to the trees.
- STEM CANKERS – Prune honeylocusts when they are still dormant in late winter to avoid stem cankers. If they must be pruned in summer, avoid rainy or humid weather conditions.
- BACTERIAL DISEASE FIREBLIGHT – Prune apple trees, including flowering crabapples, mountain ash, hawthorns, and shrub cotoneasters in late winter in February to early April. Spring or summer pruning increases the chances for infection and spread of the bacterial disease fireblight. Autumn or early winter pruning is more likely to result in drying and die-back at pruning sites.
- BLEEDING – Some trees have free-flowing sap that “bleeds” after late winter or early spring pruning. Though this bleeding causes little harm, it may still be a source of concern. To prevent bleeding, prune the following trees after their leaves are fully expanded in late spring or early summer. Never remove more than a quarter of the live foliage.
Trees that benefit the most in late winter pruning are all maples, including box elder, butternut, walnut, birch and its relatives, ironwood, and blue beech.
Here is a list of trees and shrubs that bloom early in the growing season on last year’s growth should be pruned immediately after they finish blooming.
- Clove currant
- Flowering plum
- Flowering cherry
- Early blooming spirea
Shrubs that bloom on new growth may be pruned in spring before growth begins. Plants with marginally hardy stems such as clematis and shrub roses should be pruned back to live wood. Hardier shrubs such as late-blooming spireas and smooth (snowball) hydrangeas should be pruned to the first pair of buds above the ground. Here’s a list of shrubs you might have that are grown primarily for their beautiful foliage and should be pruned IN SPRING before new growth begins:
- Alpine currant
- Burning bush
- Purpleleaf sandcherry
After the first pruning at planting, hedges need to be pruned more often. Once your hedge reaches your desired height, always prune new growth back whenever it grows another six to eight inches. Prune to within 2 inches of the last pruning. Hedge pruning may be done twice a year, in spring and then, again in mid-summer, to keep them dense and attractive.
Prune hedges so they’re wider at the base than at the top, to allow all parts to receive sunlight and prevent legginess.
For older shrubs or overgrown shrubs, prune them every year and remove up to one-third of the oldest, thickest stems or trunks, taking them right down to the ground. This will encourage the growth of new stems from the roots. Once there are no longer any thick, overgrown trunks left, switch to standard pruning as needed.
Deciduous shrubs that have multiple stems (cane-growth habit), and that have become very overgrown or neglected can be rejuvenated by cutting all canes back as close to the ground as possible in early spring. This season’s flowers may be sacrificed but the benefits from bringing the plants back to their normal size and shape outweigh this temporary collateral damage. This pruning technique works best for shrubs such as overgrown spirea, forsythia, cane-growth viburnums, honeysuckle, and any other multiple stemmed shrubs that are otherwise healthy. Within one growing season, these shrubs will look like new plantings, full and natural shaped.
With few exceptions, evergreens or conifers require little pruning. Different types of evergreens should be pruned according to their varied growth habits.
Spruces, firs and douglas-firs don’t grow continuously, but can be pruned ANYTIME because they have lateral (side) buds that will sprout if the terminal (tip) buds are removed.
Though you can prune them anytime, it is probably best to prune them in late winter, before growth begins. Some spring pruning, however, is not harmful.
Pines only put on a single flush of tip growth each spring and then stop growing. Prune before these new needles become mature. Pines do not have lateral buds, so removing terminal buds will take away new growing points for that branch. Eventually, this will leave dead stubs.
Pines seldom need pruning, but if you want to promote more dense growth, remove up to two-thirds of the length of newly expanded candles. Don’t prune further back than the current year’s growth.
Arborvitae, junipers, yews, and hemlocks grow continuously throughout the growing season. They can be pruned any time through the middle of summer. Even though these plants will tolerate heavy shearing, their natural form is usually most desirable, so prune only to correct growth defects.
Do you need help with pruning? It is always best to get recommendations from professionals and to get help from tree experts when taking care of your trees. Click the button below to get a free consultation for your trees and shrubs.