Photo credit: Michele MacKinnon
Photo: Gloves and pruning shears
Dread. Fear. Patience. The word “pruning” elicited these responses from nearly 40 people who attended my recent presentation, “Fearless Pruning - Confident Care of your Trees and Shrubs.”
Knowing that pruning benefits most plants and is a requirement when dead, damaged or diseased material is present may alleviate concern.
First, let’s dispel some common myths, including: most plants need annual pruning; shearing saves time; and wound paint should be applied after a tree limb is removed.
Keep safety in mind
Since we’re discussing the painless aspect of this garden task, just a few reminders: Wear long pants, sturdy boots, safety glasses, and gloves. Always hire a professional arborist for large trees or when you’re seeing signs of a tree’s decline, such as visible gaps in the foliage of shade trees. Avoid power lines and other utility connections as you work.
How much material can be removed?
Generally, limit the amount removed to a third of the plant’s material. Another approach is to keep the same amount of newer canes or main branches as older growth removed. In the case of suckering shrubs (lilac, summersweet) or cane shrubs (forsythia, Arctic Willow) remove a portion of the oldest material each year. After a three-, four- or five-year cycle the plant will be completely renewed. Allow longer cycles for overgrown shrubs or plants showing signs of decline or poor health, which will prevent undue stress on the plant.
Is there an ideal time to prune? There is no single answer here. However, a practical rule of thumb is to avoid heavy pruning in late spring and early summer when a plant’s energy is depleted from pushing out new growth. Dead, diseased, dying, damaged, or crisscrossing, rubbing and wrong-way branches may be removed at any time of year.
The next major consideration for common flowering landscape shrubs is when they bloom. Shrubs that bloom on “old wood,” from buds set the previous year, usually do so by the end of June. Examples are forsythia, lilacs and Bridal Wreath spirea, and they should be pruned soon after flowering. Shrubs flowering after July 1st or grown for their berries, including butterfly bush, smooth or panicle hydrangeas and Rose of Sharon, should be pruned in early spring as soon as buds are swelling. They produce flower buds on “new wood,” from buds set the current year. Find helpful tips for this group of plants at Pruning Early Flowering Shrubs (from the UConn Home & Garden Education Center). Rhododendrons, azaleas, Mountain Laurels and pieris may be pruned in the same fashion.
Avoid pruning needled evergreen shrubs and trees, except to maintain their natural shape. Aggressive pruning can harm or kill trees. Find guidance on varieties familiar to most homeowners on the following websites: How To Prune Coniferous Evergreen Trees, Pruning Evergreens (from the Wisconsin Horticulture Extension) and Pruning Evergreens (from the Morton Arboretum). For pictures and advice from a public garden expert, see Conifers: Pruning, Best Cultivars and More, with Longwood’s Ginny Levy.
Among numerous pruning books, a few to consider are The Pruning Book: Completely Revised and Updated by Lee Reich and Pruning Made Easy, A Gardener's Visual Guide to When and How to Prune Everything, from Flowers to Trees by Lewis Hill. You can also watch numerous pruning videos by PlantAmnesty.
Michele MacKinnon, is a UCONN-Certified Advanced Master Gardener, garden educator and speaker, and Sierra Club member. For tips on making better choices at the garden center this year or to ask gardening questions, email email@example.com.