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What to Prune, When?
by Charlotte Kidd - posted 01/30/12


Leave ornamental grasses upright for attractive winter interest and as protective winter
habitat for small animals and birds.

The sky is clear. The sun is bright. The weather is ideal for pruning. You’ve found pruners, loppers, pruning saw, gloves, paper trash bags and string. Walking around the yard, you scan your garden, trees and shrubs. You’re puzzled. What DO you prune, and WHEN should you prune it?

Pruning is one of my favorite activities. After 15 years of professional gardening, I still pause, survey the landscape then decide what to do in the available hour or three. Here are some tips and thoughts.

 

Pruning Basics


Disinfect pruners, saw and lopper blades with isopropyl alcohol, chlorine bleach solution or a strong household disinfectant. Do this as often as possible to reduce the spread of diseases and insects to plants you're pruning.

Always wear gloves to protect fingers and reduce possibility of hand injury.

Keep a bottle of isopropyl alcohol, diluted chlorine bleach, or disinfectant handy to clean cutting blades between plants. Spray or pour disinfecting liquid on the blades to remove fungi, insect eggs, infected or infested plant debris. Clean blades will not spread a pest or disease from one plant or shrub to another.

Pruning stimulates growth. Before pruning live branches, ask yourself. “Do I want this shrub or tree to grow now?” Clipping off branch tips removes hormones that control growth below. The woody plant will respond in kind, elongating existing branches and activating new branches and buds below.

Invest in a topnotch pruning book with clear photos, explanations and instructions. I rely on my dog-eared, 1997 softcover edition of The Pruning Book by Lee Reich, (Taunton Press, 1999). Fortunately Taunton has reissued this practical and sturdy “How To.” Reich’s direct, clear writing style and the book’s photos and clean line drawings make this an excellent intro for the novice and a smart reference for those of us in training.

Helpful pages from pruning guru Reich's book, The Pruning Book (Taunton Press), are viewable on the web at Google Books.

 

Winter Snipping, Pruning and Sawing

Prune anytime to remove dead, dying and broken branches.

Clip off butterfly bush (Buddleia spp.) seed heads. Butterfly bush is considered an invasive plant because the seeds spread and sprout so successfully. Do not remove the branches till spring.

Cut dead perennial stems back to 4 to 6 inches. Remaining short stems allow leaves and snow to accumulate above the crown and protect it through winter’s freeze-and-thaw cycle.

Saw off watersprouts on trees. Watersprouts are errant, fast-growing, usually vertical shoots taking a right angle from a tree’s healthy scaffold branches. They divert energy from the tree’s overall growth. For crossing, errant or other unwanted branches, saw just outside the branch bark collar — the protective bulge where branch joins trunk. The branch bark collar will provide protective hormones for the cut to heal.

 

Formative Winter Pruning


Saw off crossing branches, suckers, branches at awkward angles and watersprouts when the tree or shrub is in winter dormancy (such as in January and February).

At the Morris Arboretum Horticulture Center, Louise Clarke is responsible for acres of meadows, woodlands and informal tree and shrub plantings. In late winter (January and February), in her position as Bloomfield Farm Section Leader she does “formative” pruning of young trees and shrubs.

Pruning a young woody plant with its mature form in mind usually involves thinning to remove excess, old or crossing branches at the trunk or at the soil line, said Clarke. Thinning opens the plant to more light, better air circulation and water penetration, she explained. Correct thinning involves squatting or sitting to reach into the shrub to saw or prune off dead, old, thick and crowded branches within 4 to 6 inches of the ground.

 

Prune Raspberries


In January, prune low to remove raspberry canes that have fruited. The fruited canes often hold some of last season's berries.

Winter is fine for pruning summer-bearing, red or yellow raspberries. Before they start growing in spring, cut to the ground any canes that have fruited. (Look for a few dried berries at the tip.) While plants are dormant, remove thin, diseased and broken canes. Canes produce best when not crowded. Good spacing is 6 inches between canes so remove canes too close to each other. The longer the canes, the more the fruit. They can reach 7 to 8 feet. Shorten only for your convenience — to fit on a trellis.

 

Resist Pruning These in Fall and Early Winter


Lacecap (and mophead) hydrangea flower clusters are beautiful alone, in winter's snow, or covered with ice. Prune to remove dead flower heads in early spring to encourage new summer bloom.


Wait until spring flowering to prune away winter-damaged hellebore leaves. Take advantage of the evergreen or semi-evergreen perennial foliage for winter color in your garden.

DO NOT PRUNE lavender or butterfly bush branches and stems till spring’s sign of viability — new green leaves.

DO NOT PRUNE ornamental grasses now. Enjoy the seed plumes and wavy stalks through winter. Cut back in spring after you see some green sprouts at the base.

DO NOT PRUNE evergreen or semi-evergreen perennials such as Helleborus spp., Heuchera spp., candytuft, Geranium ‘Biokova’, Dianthus spp. and common sage. Their foliage can be attractive until winter’s end. In spring, clip off dead leaves and tips.

DO NOT PRUNE ROSES NOW. DO NOT CUT long canes on climbing roses. Tie up canes though so they don’t whip around in winter wind. Hold the pruners until late February or March, when the forsythia blooms. Then consult an excellent pruning book, the Internet or videos for instructions.

DO NOT CUT BACK hydrangeas. Pruning or removing hydrangea branches may be removing the buds for next summer’s flowers. Unless you know your hydrangea blooms on new wood, only cut away dead stalks at the shrub’s base.

EVERYONE HAS TO EAT. Leave food for wildlife. Leave the viburnum, cotoneaster, ilex and hawthorn fruits on the plant. Keep the rose hips intact, as well as the ornamental grass and flower seed heads. Provide some protective habitat for wildlife. Birds, insects and small animals will nestle in clusters of dead branches and debris through winter.

 

 

 


Charlotte Kidd, M. Ed. is a writer, professional gardener, garden designer and garden coach. She’s a member of the Society of Environmental Journalists and the Garden Writers Assoc.