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Seasonal care of trees & shrubs: Pruning deciduous branches

SeasonalCare_22x28_seasonsSeasonalCare_deciduousbranchesSeasonalCare_22x28_key

How to prune trees is an excellent publication designed to illustrate the types of pruning that can be done, how pruning cuts are made, when to prune different plants, and more.

Shrubs:
Pruning cuts made to deciduous shrub branches are the same as pruning cuts made to all trees; however, types of pruning styles are special for deciduous shrubs.  How to properly prune deciduous shrubs (.pdf) highlights techniques of thinning, rejuvenation, shearing, pinching and deadheading. Shrubs to Behead details the strategy of rejuventation pruning along with species that respond best to this treatment.

Trees:
Waiting until the plant is dormant is the safest time to do any live-branch pruning.  However, unless the tree or shrub is susceptible to infectious disease (e.g., oak wilt, fire blight), removal of weak, diseased, crossing, rubbing, or dead limbs can be done throughout the year if needed.

The following table is grouped by infectious diseases and is a partial list of trees and shrubs that should NOT be pruned during the SPRING to EARLY FALL:

Northern species affected by oak wilt Species affected by fire blight
White oak (Quercus alba) Mt. Ash (Sorbus spp.)
Bur oak (Quercus macrocarpa) Cotoneaster (Cotoneaster spp.)
Swamp white oak  (Quercus bicolor) Hawthorne (Crataegus spp.)
Chinquapin oak (Quercus muehlenbergii) Quince (Cydonia sp.)
Northern red oak (Quercus rubra) Serviceberry (Amelanchier spp.)
Northern pin oak (Quercus ellipsoidalis) Firethorn (Pyracantha sp.)
Black oak (Quercus velutina) Spirea (Spiraea spp.)
Scarlet oak (Quercus coccinea) Pear (Pyrus spp.)
Chestnut oak (Quercus montana) Crabapple and apple (Malus spp.)
Blackjack oak (Quercus marilandica) Lilac (Syringa spp.)
Shumard oak (Quercus shumardii) Cherry (Prunus spp.)
Shingle oak (Quercus imbricaria) Apricot (Prunus spp.)
American chestnut (Castanea dentata) Chokecherry (Prunus spp.)
Tanbark oak (Lithocarpus densiflorus)
Southern species affected by oak wilt
Live oak (Quercus virginiana)
Scrub live oak (Quercus fusiformis)
Southern red oak (Quercus falcata)

Water oak (Quercus nigra)

Spanish oak (Quercus buckleyi)

For more information: How to Identify, Prevent, and Control Oak Wilt; Fireblight

Pruning of the following listed diseases and affected plants should not be done during WARM, WET periods of the year (i.e. spring).

Species affected by black Knot Species affected by cankers
Black cherry (Prunus serotina) Tree of heaven (Ailanthus altissima)
Common chokecherry (Prunus virginina) Hickory (Carya spp.)
Wild plum (Prunus americana) Dogwood, flowering (Cornus floria)
Holly, American (Ilex opaca)
Walnut (Juglans sp.)
Elm (Ulmus spp.)
Oak (Quercus spp.)
Persimmon, common (Diospyros virginiana)

Elm Trees: Elm pruning and Dutch elm disease (DED) management should be left to certified arborists.

A recommendation on when healthy (non-DED infected) elm trees should be pruned in order to decrease the chances of Dutch elm disease transmission through elm bark beetle flight is unclear. Some experts advise that pruning of healthy elm trees can be done at any time because the pruning wound does not attract beetles; however, other experts warns that healthy elms should be pruned only during the dormant season because the beetles are attracted to pruning wounds.

Sources of related information:

  • Byers, J.A., P. Svihra, and C.S. Koehler. 1980. Attraction of elm bark beetles to cut elm limbs on elm. J. Arbori. 6: 245-246.
  • Dreistadt, S.H., Dahlsten, D.L., and G.W. Frankie. 1990. Urban forests and insect ecology: Complex interactions among trees, insects, and people. BioScience 40(3): 192-198.
  • French, D.W., Ascerno, M.E., and W.C. Stienstra. 1980. The Dutch elm disease. U of MN, MN Ext. Ser. AG-BU-0518.
  • Haugen, L. 1998. How to identify and manage Dutch elm disease. USDA Forest Service NA-PR-07-98.
  • Landwehr, V., Phillipsen, W., and M. Ascerno. 1981. An integrated approach to managing native elm bark beetle populations in Minnesota. pp. 454-463. Proceedings of the Dutch elm disease symposium and workshop. Manitoba Department of Natural Resources, Canada.
  • Landwehr, V.R., Phillipsen, W.J., Ascerno, M.E., and R. Hatch. 1981. Attraction of the native elm bark beetle to American elm after the pruning of branches. J. of Econ. Ent. 74(5): 577-580.
  • Schomaker, M., Leatherman, D.A., and W.S. Cranshaw. Accessed 2006. Dutch elm disease. Co. State Univ. Coop. Ext. no. 5.506.

More information on seasonal care:

Authored by Rebecca Koetter, Gary R. Johnson, and Dave Hanson: University of Minnesota
Funded in part by USDA Forest Service: Northeastern Area
Chart designed by Andrew Rose: www.handeye.us

Download & print your own poster or magnet copy of the “Seasonal Care for Trees and Shrubs in Northern U.S. Climates”

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3 Responses to “Seasonal care of trees & shrubs: Pruning deciduous branches”

  1. SKS says:

    We have a very healthy elm tree on our boulevard that is overgrown (low hanging branches) and needs to be trimmed. There few healthy elm trees in our city (Fairmont, MN).

    What is the best time of the year to trim this tree?

    The city has agreed to trim it but is concerned about the tree becoming infected. I think they want to treat the cuts.

    Your recommendation.

    Thanks.

  2. Rebecca Koetter says:

    Dear elm pruning question,

    The best time to do any live-branch pruning of trees is during the late dormant season, which we’re coming up to in Minnesota (Feb-March). So if they can wait just a little longer that would be the safest time for your elm tree.

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