Best time to prune trees – Do´s and don’ts during 4 seasons

prune trees and plants

Pruning & trimming seasons

As fall sneaks it’s little head around the corner, it brings upon yet another season to prune and trim your trees and plants.  In Minnesota, one of our most prevalent trees is the Oak tree.  As avid forest preservationist, we strive to protect any and all trees. We know that Oak Wilt is a very progressive disease.  Please see our Oak Wilt blog for further information. 

November to April

We are currently in the “Low” season for Oak Wilt. However, that will be changing up here soon as those cold nights become more and more frequent.  We like to only trim Oak trees between the months of November and April when the University of Minnesota deems is “Safe”.  Of course as we all know, the weather around here has a tendency to change. So those months are simply a light guideline.

To avoid stem cankers, prune Honey Locusts when they are still dormant, in late winter.  If your Honey Locust needs attention throughout the year, avoid overly humid and rainy weather. 

Prune late winter, February to early April

Prune Apple Trees, including flowering Crab Apples, Mountain Ash, Hawthorns and shrub cotoneasters in late winter, February to early April.  Spring and summer pruning increases the chances for infection and the spread of the bacterial disease Fireblight.  Fall or early winter pruning is more likely to result in drying and die back at pruned sites.

Perhaps you can start to see a trend here with our long winter coming up!  It is a wonderful time to clean things up.

Some trees have free-flowing sap that “bleeds” after late winter or early spring pruning.  Through this “bleeding” causes little harm, it may still be a source of concern for our clients.  Rest assured this is a normal and we will be more than happy to stop back out to your property to educate you on the natural functions of your tree after pruning takes place. 

Prune late spring & early summer

To prevent bleeding, prune the following trees after their leaves are fully expanded in late spring into early summer.  Also remember we here at Alliance Tree Care Inc generally practice not removing more than ¼ of the live foliage.

  • All Maples, including Boxelder
  • Butternut and Walnut
  • Birch along with Ironwood & Blue Beech

Prune after the finish blooming

Trees and Shrubs that bloom early in the growing season on last year’s growth should be pruned immediately after the finish blooming.  This list is a great reference for our Minnesota hardy growers in zones 3A, 3B, 4A and 4B.  This is a wide range of cold temperatures from -40 to -28.9 below zero.

  • Apricot
  • Azalea
  • Chokeberry
  • Chokecherry
  • Clove Currant
  • Flowering Plum
  • Flowering Cherry
  • Forsythia
  • Juneberry
  • Lilac
  • Magnolia
  • Early blooming Spirea

Spring

Trees and shrubs to prune before new growth, shrubs grown primarily for their foliage rather than shower flowers should be pruned in spring, before growth begins.

  • Alpine Currant
  • Barberry
  • Buffaloberry
  • Burning Bush (a new addition to the MN noxious weed list as of 2020, in 2023 it will be on the Restricted Noxious Weed list meaning no more sale, propagation or transportation in MN)
  • Dogwood
  • Honeysuckle
  • Ninebark
  • Peashrub
  • Purpleleaf Sand Cherry
  • Smokebush
  • Sumac

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 life wood.  Hardier shrubs such as late blooming Spiraeas and smooth (Snowball) Hydrangeas should be pruned to the first pair of buds above the ground.

Pruning Hedges

After their initial pruning at planting, hedges need to be pruned often.  Once the hedge reaches the desired height, prune new growth back whenever it grows another 6” to 8”.  Prune to within 2 inches of the last pruning.  Hedges may be pruned twice a year, in spring and again in mid-summer to keep them dense and attractive.  Prune hedges so they’re wide at the base than at the top.  This allows all parts of the shrub to receive sunlight and prevent legginess.  A perfect example of this is the Arborvitae and Arborvitae like smaller shrubs Cypress and Juniper.

Older Shrubs

For those of you that have some older, less maintained shrubs, every year you can 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 and thick, overgrown trunks left, switch to standard pruning as needed. 

Deciduous shrubs with multiple stems

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.  That seasons flowers may be sacrificed. However, 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, Forsythis, 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.

Evergreens

With few exceptions, Evergreens (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 continually, but can be pruned any time because they have lateral (side) buds that will sprout if the terminal (tip) buds are removed.  It’s probably best to prune them in late winter, before growth begins.  Some spring pruning, however, is not harmful.

Pines

Pines only put on a single flush of top growth each spring and then stop growing.  Pine 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 stumps.  Pines seldom need pruning, nut 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.  

Pumpkins

While the everything pumpkin starts to be sold everywhere and the scents of Apple Pies fill the air, lets take a moment to make sure our fall clean up gets done right.  We are currently booking into the later part of October, however there are a few smaller appointments still available.  If you need some heavier tree work completed, we can also accommodate you before the snow flies. 

General guideline

Please take this advise as a general guideline to not only what we attempt to follow on a daily basis, but there are always extenuating circumstances, inclement weather changes (the draught of 2021). And of course the “eye” of an Arborist vs the “eye” of a homeowner.  Together we can always come up with the best plan for pruning your trees and shrubs for health, aesthetics and happiness to all involved. 

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