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Garden Help Desk: Should I start pruning my trees?

By USU Extension - | Dec 31, 2022

Courtesy Meredith Seaver

Topping a tree or cutting branches back with poor pruning cuts can cause vigorous, uncontrolled, and poorly attached new growth, leaving the tree taller or with more problems than it had before being topped or pruned.

Is it time to prune my tree and shrubs?

That depends on what kind of trees and shrubs you have.

Mid to Late January is the time to prune shade trees if you need to. Shade trees don’t need to be pruned annually like fruit trees and we often do more harm than good with unneeded pruning. Good reasons to prune a shade tree include removing limbs that are diseased or dead, those that pose a danger- blocking visibility or if they are likely to fall on a home, car, etc. Do not remove more than 20% of canopy wood from shade trees if pruning is needed.

Make sure any pruning that must be done on one of your shade trees is done properly. A bad pruning job will create more problems than the one you tried to correct. Never just cut a branch back part way. Instead, a problem branch should be cut completely back to the branch it’s growing from, or back to a healthy branch (not twig) that’s growing from the branch that needs to be partially removed. Don’t top a tree to reduce its height! Instead, consult a Certified Arborist about doing a crown reduction with proper pruning cuts.

Unlike shade trees, fruit trees need to be pruned annually to promote fruit production. Mid to late February is the time to prune apples, pears, and fruiting quince. They are more adapted to being pruned in colder weather and early pruning also helps avoid a disease called fire blight that can be especially fatal in pears and quince. Cherries, peaches, plums, and other stone fruits should not be pruned until mid-March. They are more sensitive to being pruned in colder weather. Do not remove more than 25% of the total canopy wood from fruit trees. The exceptions to this are peaches and nectarines. Up to 40-50% of the wood can be removed from these trees, depending on how they grew the previous year.

Courtesy Meredith Seaver

When winter weather is cold and wet, it's hard to remember how important a good layer of chipped wood or bark nuggets will be in the summer.

Mid-March is also the time to prune roses you would use as cut flowers indoors, such a floribunda and hybrid tea types. Cut them back to between knee and thigh high and thin the canes to 3-4 main canes. Everblooming shrub roses can also be given a haircut at this time.

Shrubs that bloom during the summer can also be pruned in mid-March, but spring blooming species like snowball bush, lilac, viburnums, bridal wreath, and forsythia shouldn’t be pruned until soon after they are done blooming. Utah state University Extension has many good YouTube videos and fact sheets about pruning that you can watch free of charge.

If I put our Christmas tree through our chipper will the mulch be too acidic to use in our shrub bed or our compost pile?

The belief that the needles from pine trees and other conifers will make soil too acidic is a common gardening myth. The needles are acidic, but they won’t significantly lower the pH of garden soil. This is especially true of our typical Utah soils, which are alkaline. Our soils are so highly buffered (resistant to pH change) that it’s very unlikely you could make a stable change to the pH in your shrub bed or garden.

Using fresh wood chips as a surface mulch in your shrub bed will help to reduce your water use by slowing evaporation and will also suppress weed seed germination, reducing your yard work for the rest of the season. Apply your wood chips in a 3-inch layer for best results.

Fresh wood chips aren’t suitable for working into your garden’s soil but the chips from your Christmas tree would be a great addition to your compost pile. If you chip your tree soon, the chips will be a nice mix of wet/green and dry/brown material. If you wait until spring, the needles will be drier, and the chips will be mostly dry/brown material.

No matter when you chip your tree, there will be a good use for them in your landscape!


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