Documents: Special Interest: Wildlife Gardening:

Pruning Evergreens Needs Careful Timing
by Marg Fleming
January 1, 2000

Few gardening activities are as specific as the correct time of year to hard prune evergreens. During the month of May, coniferous trees and shrubs develop new growth and are in a general state of renewed vigour after the long winter. Consequently, these plants have a strong ability to recover from severe pruning at this time. Still cool temperatures prevent excess moisture loss from plants stressed by surgery. New little feeder roots formed earlier this year assist in the development of new growth encouraged by pruning.

When cutting back evergreens to reduce their size, remember that most of them will not produce any new growth from old wood. If pruned down too far, most specimens will never regain an attractive shape. Often, those relieved of foliage in sizeable quantities will die, deprived of the means by which they produce sustaining sugars.

Prune evergreens carefully. Leave enough "green" in strategic places to maintain the health of the plant and to retain its shape.

During the pruning process, you may find that removing substantial amounts of the green is unavoidable if the specimen is to be reduced to a desired size. It is then time to consider complete removal of existing shrubs and replanting with younger, fresher specimens. Old foundation plantings characteristically develop a skeleton-like, woody framework. A very thin, green icing of new foliage hides the old scaffolding. Any pruning creates windows through which the old, ugly stalks become clearly visible. Time to redecorate. Remove those tired, old shrubs and replace with new. Try something different this time to create a new look. Little Potentilla shrubs never seem to go out of style. Try variegated euonymous for a non-coniferous evergreen. Corkscrew hazel adds a little interest to any front bed, winter and summer. Be a bit daring in your foundation overhaul, but resist over-planting. The temptation exists to install several shrubs where there is growing space for only one. The instant effect is a full, attractive landscape display. But it will be money wasted when, in two or three years, the shrubs quickly begin to crowd each other for growing space.

Where two shrubs touch, their classic shapes are both spoiled and foliage begins to die at the union. Frequent pruning to maintain characteristic shrub shapes creates coarse, unattractive branching and continuously risks entry by disease.

Give shrubs ample room into which they may attain their mature size. Large clusters of young shrubs may be attractive immediately, but wasted time and money will be realized in a very short time.

Spiraea shrubs are in leaf now and will soon give their encore performance of lovely, cascading, white blooms. Spiraea becomes quite large and woody with age. Large plants tend to fall apart under their own weight spoiling the typical Spiraea shape. Often, gardeners tie the large toppling stems together in the interior of the shrub to maintain its integrity. This is not necessary. Nor is it necessary to remove the specimen and replant a newer model.

Spiraea should be rejuvenated periodically by reducing some of the stems to about 18 inches above ground level. Remove all the oldest and largest stems leaving the younger more vigorous stems to regenerate. Start the operation immediately after the shrubs bloom. This year's flowers can then be enjoyed, and there is enough time for the plant to renew itself before winter ensuring a good show again next spring.

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