Released: February 15, 2002

Also see: Early Spring, 2002 Yard 'n Garden news package

Plant Health and Looks Both Reasons to Prune
Sidebar: "When to Prune"

MANHATTAN, Kan. – Trees and shrubs with damaged or dead limbs are an open invitation to insects and disease. Too often, however, homeowners delay pruning until ornamental plants look odd, ugly, sick or downright dangerous.

"Damage and looks both are legitimate reasons. Nonetheless, ornamentals often need fairly regular care with nippers or saw – if nothing else, to avoid bigger problems in the future. The bigger the ornamental, the more likely major pruning is to be stressful for the plant and costly for the homeowner," said Charles Barden, forester with Kansas State University Research and Extension.

Trees and shrubs both need pruning, Barden said, when any of the following develops:

* A branch grows "crossways," so that it rubs against and damages other limbs’ bark.

* Fast-growing "water sprouts" shoot out to compete with established branches.

* Sprouts emerge below the trunk’s graft line (from the root stock, which isn’t able to produce branches that look or perform like the grafted-on upper plant’s).

* Weather or other factors badly damage limbs.

Trees have additional needs, however.

"Most large-growing trees need a central leader or trunk. When a tree develops multiple leaders, you must select the one that looks strongest or has the best shape and then prune out its competition," he said. "You may also want to remove branches with narrow V-shaped crotches connecting them to the trunk. Their removal can open up the crown so strong winds can blow through without major damage. It also will leave the strongest branches in place – those with a joint that’s almost a right angle."

Other reasons to prune trees include:

* To improve architecture – a tree’s overall shape.

* To remove branches that cut off breezes, block a view, keep turf in the dark, or interfere with lawn mowing.

"Just be sure that you never remove more than one-third of the crown at any one time. Don’t prune so drastically that a newly bare trunk suffers sunscald, either," Barden advised. "And remember: The younger the tree, the better. After all, when a sapling puts out a lateral limb 3 feet from the ground, that limb still will be 3 feet from the ground when the tree’s full-grown. But the older version will be a lot more stressful and difficult to remove."

Pruning for trees means removing some branches at the crotch, not shortening all branches and not topping or shearing off limbs that are making a tree "too tall."

"Topping a tree immediately lessens its value. It will never be as attractive. It will never be as strong, either, because ‘topping’ encourages new, weak and even taller whip-like growth," the forester said.

The reasons for pruning shrubs are similar, Barden said, but can lead to more drastic cuts:

* To remove winter kill or other damage.

* To control size or shape.

* To encourage fuller branch growth.

* To open up the center and allow access to more light and air flow.

* To give an old, declining shrub new life.

* To remove the fading flowers and developing seed pods that can sap the shrub’s energy for developing next year’s growth and/or flowers.

Shrubs with a single trunk require the lightest hand. Pruning should take no more than about a third of their growth, unless these shrubs already are severely damaged, the forester said.

Multi-stemmed shrubs – such as forsythia, spirea, ninebark, mockorange, shrub rose and quince – will recover with new, thick growth, even if pruned down 6 to 12 inches from ground level.

"With either type of shrub, make all cuts just above a crotch or bud, aiming to retain the shrub’s natural shape, not shear every branch to the same length. If you only prune above outward-facing buds, you’ll also encourage outward, less crowded growth," Barden advised. "With multi-stemmed shrubs, however, always start by removing the dead canes or limbs. You can cut them off at ground level or where they join onto a living, healthy branch."

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When to Prune

Deciduous Trees

Shade -- Anytime; often easiest while dormant

Spring-flowering -- Just after blooming

Summer-flowering -- Winter/very early spring

Evergreens

Needleleaf

Arborvitae -- Before new growth (often mid-March - April)

Fir -- Only to remove injured/diseased branches

Juniper -- Early spring

Pine -- Late spring; when needles are starting to grow

Spruce -- Best in early spring before new growth begins

Broadleaf

Non-Flowering -- Early spring, if really necessary

Flowering -- Just after blooming, if really necessary

Shrubs

Non-Flowering -- While dormant best, but before midsummer

Spring-Flowering -- Just after blooming

Summer-Flowering -- While mostly dormant (late winter - early spring)

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K-State Research and Extension is a short name for the Kansas State University Agricultural Experiment Station and Cooperative Extension Service, a program designed to generate and distribute useful knowledge for the well-being of Kansans. Supported by county, state, federal and private funds, the program has county Extension offices, experiment fields, area Extension offices and regional research centers statewide. Its headquarters is on the K-State campus, Manhattan.

Story by:
Kathleen Ward, Communications Specialist
kward@oznet.ksu.edu
K-State Research& Extension News