01/22/10
Renewal Pruning Deciduous Shrubs
 The foggy winter mornings we had earlier this week left a fleeting but gorgeous shimmering coat of frost on every twig and branch in my yard. It made me really slow down and have a good look at the branches of my landscape plants. Deciduous trees and shrubs (those that lose their leaves for winter) aren’t usually grabbing much attention at this time of year. However, their bare bones make this a great time to assess their branching structure to plan for spring improvement and renewal with proper pruning.
What is Renewal Pruning?
Renewal pruning is used to maintain existing shrubs and keep them growing at their best for many years. It is also used to give overgrown, tired-looking shrubs a new lease on life when they are getting along in years. First of all, unless you are maintaining a hedge into a certain formal, pre-determined shape, a hedge shear should never get near your deciduous shrubs! Hacking off the top of your plants all at the same level is definitely the easy way out, but is not a long term solution. This practice causes many new shoots and leaves to sprout all at the same level from growing points, or nodes, just below the fresh cuts. Although this new growth might look good for one season, this abundance of leafy growth will get over-crowded, causing potential leaf disease problems. More importantly, this crowded growth will shade out the bottom leaves on your shrub causing them to drop off, giving your plant a leggy, naked appearance on the bottom. Unless you are going for this odd, leggy, Dr. Seuss-style landscape, the proper way to prune shrubs is with a sharp hand pruner (or lopper or saw if the branches are older and thicker), removing individual branches at their base as close to the crown of the plant (ground level) as you can get. Renewal Pruning Plan of Attack:- Pruning tools in hand, stand back and take a good look at your shrub(s) from many different angles to take in the overall shape.
(Plants grow in the shapes and sizes which they are genetically programmed for, and it is best not to fight this too much. If you don’t like the overall habit, proper pruning is never going to override genetics, so you might consider just replacing the plant! Consult your local landscape professional for recommendations.)
- Remove any broken branches or any branches showing evidence of disease (obvious cankers, fungal growth, etc.).
- Remove any branches that cross others causing rubbing or mechanical damage.
- Remove any branches that are growing awkwardly towards the center of the plant or towards the ground rather than up and out from the center of the shrub.
- Stand back and take another good look at your progress. In renewal pruning, you want to remove about 1/3 of the total branches each year in order to give plenty of air circulation and light infiltration into the center of your shrub. If you have not yet thinned out your shrub by 1/3, remove more branches, starting with the oldest, until you are satisfied. Do not be shy, tough love is required for this process and your shrubs will thank you with healthy growth in the end.
Timing of Pruning
In general, shrubs that bloom in early spring, such as lilacs and forsythia, are best pruned immediately after spring flowering is finished. These plants initiate next spring’s flowers during their summer growth, so pruning too late will actually remove next year’s potential blooms. Sometimes the need for renewal for overall plant health outweighs missing the flower show for one spring. To prune or not to prune, that is the individual gardener’s question! I like to prune summer blooming shrubs such as Spirea, Hydrangea and Roses in spring just as their leaves are starting to come out. This way I can assess their structure as well as remove any winter tip dieback at the same time. After making my renewal cuts, I will check the remaining branches for any buds that are not sprouting and cut them back to just above the nearest green, sprouting growth. Shrubs grown mainly for their foliage rather than for their flowers can be renewal pruned anytime during the season. However, it’s always easier to see what you are cutting before spring leaf growth flushes out completely. For more information about proper pruning, visit:
http://www.extension.umn.edu/distribution/horticulture/DG0628.html. To consult with a tree care service, find one near you with this Find an Expert search.
by Stephanie Girgen
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