PUEBLO, Colo. — With the holidays behind us, spring is right around the corner. It might seem too soon to start thinking about the outdoors, but it is actually the perfect time to start thinking about pruning your trees and shrubs. Timing is key when it comes to pruning. You also need to consider what you are pruning and what your goals are.
Any dead, diseased, or damaged tissue on a tree can be removed any time of year. If you are doing very light pruning (less than 10% of the foliage) of live wood, that can also be done at any time of the year. Late winter is considered the routine time for pruning mature trees, before the buds start to swell. Some trees like Elms, Hackberry, Maples, and Mulberries may “bleed” when pruned in late winter. This a cosmetic concern, but if you prefer to wait to prune these species, you can prune them midsummer, after the spring growth flush.
Young shade trees require very little pruning if any, but the training a tree receives when it is young will determine its structure for life. Late winter is the perfect time to do some structural training of a young tree. CSU Extension has a multi-page document that describes in detail how to properly train a young tree, it can be found here: http://www.ext.colostate.edu/mg/Gardennotes/613.pdf.
Spring flowering shrubs such as forsythia, viburnum, lilac, and honeysuckle bloom on the twigs that grew the previous summer. The flower buds develop starting in midsummer and go through the fall to make buds for the following spring. If you were to prune these shrubs in the in the fall or now, you would be removing the wood with next year’s buds, which would prevent flowering. To thin these shrubs, prune right after they bloom. It is also recommended to deadhead spent flowers so the plant can focus energy on foliage and new buds rather than making seed pods.
Summer flowering shrubs like butterfly bush, blue mist spirea, and rose of Sharon bloom on wood that grew earlier in the same growing season. These types of shrubs set buds in mid to late spring, and then bloom in the summer. You can prune summer flowering shrubs now into early spring before growth begins. Removing older wood will allow better sunlight penetration, and will encourage flowering throughout the shrub, rather than just on the top where there is a lot of sunlight.
Pruning large, mature shade trees is often a task that can become unsafe for most home gardeners. Hiring a professional to handle these large pruning jobs is the safest approach. Look for an arborist that is certified by the International Society of Arboriculture (ISA). You can find a list of ISA certified arborists here: http://www.treesaregood.org/findanarborist.
— Sherie Caffey, CSU Extension-Pueblo County Horticulture Agent
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