Published on January 8, 2008
Pruning Trees and Shrubs: Pruning Trees and Shrubs Rick Abrahamson University of Minnesota Extension Clay County When should trees and shrubsbe pruned?: When should trees and shrubs be pruned? January - February: January - February Oak Oak Wilt Elm Dutch Elm Disease March: March Oak Ash Ash borer Birch Bronze Birch borer Early April (1st – 15th): Early April (1st – 15th) Fireblight control Apple/crabapple Mountain-ash Cotoneaster Shade and ornamental trees Hackberry Linden Poplar Stem canker control Honey-locust Slide6: Early April (1st – 15th) Shrub flowering habits Hydrangea Bush Honeysuckle Spireas (summer) Foliage shrubs Alpine currant Barberry Dogwood Viburnum Evergreens Spruce Late April (15th – 30th): Late April (15th – 30th) Flowering habits Apricot Chokecherry Flowering Cherry Juneberry (Serviceberry) Forsythia Evergreen Arborvitae Juniper Yew May - June: May - June Flowering habits Flowering Plum Japanese Tree Lilac Chokeberry Lilac Mockorange Potentilla Spirea (early) Shrub Rose Slide9: May - June Bleeding Maple Boxelder Black Walnut Ironwood Weeping Willow Kentucky Coffee Tree Evergreens Pine July - August: July - August Evergreens (don’t prune after August 15th) Arborvitae Yews Juniper September - December: September - December Leave pruning tools in storage Healing of wounds slower in fall Drying and dieback more likely Decay fungi spread high Exception Oak and Elm Slide12: That’s good information, but… How should trees and shrubs be pruned? Prune for function: Prune for function Broken, diseased, and dead Obstructing limbs and branches Clear doors and windows Form, shape, vigor, and beauty Why prune?: Why prune? Control habit of growth Remove dead, broken, and diseased Produce desired shape and form Improve flowering and fruiting Improve survival rate Pruning equipment: Pruning equipment Hand Shears Pruning Loppers Pruning Saw Pole Tree Saw Slide16: Pruning equipment No buckets, ladders, or boxes!!!!! Stay on the ground!!!!! Get professional help, know what you want and make sure it is done right. Botany of pruning: Botany of pruning Branches elongate from buds Branches increase in diameter from the cambium Where to cut?: Where to cut? Grow your plants by choice, not by chance. General pruning: General pruning Keep diseased, broken, and dead branches pruned out at all times Avoid weak crotches Remove cross over and interfering branches Prune to side branches or main trunks Never leave stubs, snags, or ragged cuts Heavy and large cuts: Heavy and large cuts Under cut Over-cut off Stub removal at shoulder ring Future of your tree: Future of your tree Weak crotch left on Pruned up to high to soon Open spreading form Prune to a central leader Future lies in your hand and your head!!! Directional pruning for trees: Directional pruning for trees Top work Reduce size Clear overhead lines Prune to side branches Stub causes “Bird nesting” Prune limbs to shoulder ring Proper cut = small wound, fast healing Flush cut = large wound, slow healing Deciduous shrubs: Deciduous shrubs Rejuvenation Induces new and compact growth Do not top!!!!!! Heading Back Reduces size Cuts made to side branches or buds! When shrubs get old and leggy: When shrubs get old and leggy Consider rejuvenation Remove half of existing old canes Next year remove remaining canes Keep new growth pinched back to induce side branching and compact growth Cut all growth back All growth new Removal and replanting May be most practical and economical Prune Junipers with a purpose: Prune Junipers with a purpose Start when plants are young Strive for a disciplined form Avoid neglect and abuse Discipline: “Training which corrects, molds, strengthens, or perfects” Prune Junipers with a purpose: Prune Junipers with a purpose Avoid sheared and ugly ends Stops terminal growth and avoids stringy growth Cut deep Back in to a top growing branch Pinch back new, young shoot growth as it develops each season Building an upright Juniper: Building an upright Juniper Single center trunk (Leader) Prune selectively Do not shear Vertically growing branches Bend for more horizontal position Head back or prune down as far as possible Building an upright Juniper: Building an upright Juniper Close branching causes crowding Remove weakest or poorest of those in conflict Rejuvenation Prune down to desired size and form Replacement may be better choice Proceed with courage! Always leave some green Building a hedge: Building a hedge Building a hedge: Building a hedge Low hedge (1-3’) Pygmy Caragana Alpine Current Dwarf Gooseberry Medium hedge (3-6’) Globe Caragana Alpine Current Dwarf Ninebark Large hedge (>6’) Honeysuckle Rocky Mountain Juniper Black Hills Spruce Common Lilac Chinese Lilac Colorado Spruce Building a hedge: Building a hedge Screening hedge (>10’) Eastern Red Cedar Flowering Crabapple Siberian Crabapple Common Lilac Amur Maple Siberian Peashrub Black Hills Spruce Colorado Spruce Time for a test: Time for a test Good luck!