The Pruning of Shrubs
This is my site Written by Geoff on March 1, 2001 – 5:36 pm

The most neglected maintenance task for most homeowner is taking care of our shrubs. Just like our homes, shrubs take a certain amount of maintenance to keep them attractive and healthy. One of the most important ways we can protect our investment is through regular pruning. Pruning is often misunderstood and improperly practiced. Proper pruning is not difficult if done regularly. A plant that has been neglected is difficult or impossible to prune. When a plant has become too large for normal pruning, it should be replaced. The use of dwarf plants reduces but does not eliminate pruning. 

The best time for pruning most shrubs is in the early spring while the plants are still dormant. Avoid major pruning in late summer and early fall, as this may force late growth that will be damaged by freezing. 

Since Spring flowering shrubs bloom on wood that matured during the previous growing season, if those branches are pruned in the fall, you eliminate the flowers that will bear next season. Therefore, always prune immediately after they have flowered. This will give your shrub the entire summer to develop flower buds for the next season. Renew main branches by cutting off old, shaggy branches that will not produce the best foliage or flowers. Cut the old branches right to the ground. Younger branches should be cut back to a bud, or to new green growth that has started during the current year. As you trim, open the center of the shrub to light and air which will encourage the plant to grow flowers on the inner branches. Some Spring flowering shrubs (March, April, May and early June blooming) are:

  1. Shadebush
  2. Common lilac
  3. Viburnum
  4. Fringetree
  5. Cranberry Bush
  6. Forsythia
  7. Weigela
  8. Mockorange
  9. Deutzia
  10. Bittersweet
  11. Flowering Almond
  12. Spirea

Summer flowering shrubs remain dormant through early spring and should be pruned at this time. They are among the last plants in the garden to recover from winter.These shrubs bloom on growth from the current year, and need to be pruned before new growth begins. Generally, prune back new growth once every spring. The best blooms will come from buds on branches that started during the previous season. By pruning young growth every year, the older branches will have newer growth at their tips. This will help it keep its shape from year to year. You should encourage some newer base branches every season so you can cut off the older, less productive branches. Most older branches will not produce vigorously beyond four years. Late-flowering shrubs (late June, July or August blooming) are:

  1. Abelia
  2. Beautyberry
  3. Vitex
  4. Barberry
  5. Rose of Sharon
  6. Butterfly bush
  7. Hydrangea
  8. Crape Myrtle
  9. Privet
  10. Summersweet
  11. Clethra
  12. Winged Euonymus

Most evergreens may be pruned in winter and early spring. Evergreens are often pruned twice: heavy cuts in early spring and a light cutting of the soft new growth in June. Evergreens should never be pruned in the summer and early fall. Prune broadleaf evergreens just before growth starts in the spring or immediately after flowering. As a general rule:

  1. Needle-leaf evergreens such as pines which produce candle-like growth in the spring, may be cut back at about half their length before it completely hardens. Shear young Mugho and Swiss Stone pines for a few years, then selectively pinch back new growth to keep the plants compact .
  2. Yews may be pruned at any time, but best results are obtained when they are pruned in the early spring before new growth emerges. The ensuing new growth will hide the pruning cuts.
  3. Arborvitaes and chamaecyparis can be pruned any time during the summer; but, care should be taken to be sure that where cuts are made, some foliage remains. Never cut back to bare wood, since the result will be unsightly.
  4. Rhododendrons, azaleas, hollies and other broad-leafed evergreensshould be pruned right after flowering as their flowers form during the summer months. Pruning that is carried out too late in the summer, will remove next seasons flowers.

A hedge must be pruned regularly to remain attractive. Most hedges need trimming at least twice a year, in the Spring and again in late summer, as soon as the new growth is complete. Some hedges may need as many as three and four trimmings a year. A dense hedge must be developed slowly. Plants such as privet or barberry need severe pruning immediately after planting and at the beginning of the second year to make them bushy. To develop a hedge that is well filled at the base, always trim so that the base is wider than the top. If the top is allowed to become wider than the base, the base will become thin and open as the top will shade out the bottom. 

Roses such as the hybrid teas, floribundas, grandifloras, hybrid perpetuals and polyanthas should be pruned in early spring as the buds are swelling but before growth has started. Remove all dead wood by cutting at least an inch below the dead area. Vigorous plants that have not been killed back should be pruned to between 18 and 24 inches. Remove all weak, thin wood at the base. Shrub roses that flower only in spring should be pruned after they have flowered. This consists of removing old canes and dead wood. Pruning of hybrid tea roses should consist of removing some of the top growth. Climbing roses should occasionally have the old canes removed. Ramblers that flower in the spring only may be pruned after flowering. Remove old, woody canes that have finished flowering at ground level. Allow new canes to remain and head back those that become too large. 

We should prune to:

  1. Improve survival chances at planting time.
  2. Control size and shape.
  3. Remove dead, diseased, weak or broken branches.
  4. Maintain natural beauty.
  5. Control flowering, fruiting or colored twig effect in certain plants.

We begin training the shrub when we first plant it with the removal of any diseased, damaged, or crossing branches. As the shrub grows, we will continue to remove such growth while trying to maintain the plant’s natural shape. You always want to maintain this natural shape unless you are trying to achieve a special effect such as with hedges, topiaries, cordons, or an espaliers. 

To maintain a plant’s health and vigor, you must regularly remove any diseased, dying, or dead wood. Unsound wood is a sure entry point for insects and diseases. Therefore, you want to make sure you cut back to sound heathy growth, preferably with a sterile blade, when pruning. Thinning out the shrub will also improve the penetration of light and air resulting in a more uniform, vigorous foliage growth. Many shrubs, such as lilacs, benefit from the regular removal of old limbs. 

Pruning will also improve the quality of flowering. When we remove some of the plants woody growth, it then can divert more energy into the production of larger, though possibly less, flowers. Since most shrubs bloom off new or one year old growth, timely pruning will increase the production of flower bearing limbs. 

Sometimes we need just to prune shrubs to keep them under control. While we should always select shrubs suitable for the space limitations sometimes, situations change. We must also keep shrubs off walks, doorways, and drives for safety considerations. Damage to the home can quickly happen if shrubs are allowed to contact siding, electrical wires, or roofing. Security is another factor we must consider when pruning. 

Some suggestions for pruning shrubs is offered by Jay Windsor Agricultural Agent,University of Delaware Cooperative Extension

  1. Barberry – Cut all 3-year-old wood back to the ground.
  2. Butterfly Bush – Prune 1-year-old wood back to a few buds. Remove all 2-year-old wood
  3. Cotoneaster – Remove only dead wood. Some tips may need to be removed to control growth.
  4. Deutzia – Remove 3-year-old wood to the ground. Remove weak growths.
  5. Forsythia – Remove 4-year-old wood to the ground. Do not remove pendulous branches until they become old and woody.
  6. Hydrangea – Prune after flowering to remove old canes. Cut flowering stems back to unflowered laterals.
  7. Honeysuckle – Prune lightly before and after blooming. Remove 2-year-old wood.
  8. Lilac – Remove seed pods, dead and diseased wood. If plants are grafted, suckers should be removed.
  9. Magnolia – Remove seed pods and practice only corrective pruning.
  10. Mockorange – Remove all 3-year-old wood to the ground. Remove spent flowering wood to a lateral.
  11. Privet – Remove 4-year-old wood to the ground.
  12. Rose of Sharon – Remove seed pods and all deadwood. Plant tends to become leggy if not trained well.
  13. Spirea – Remove all 3-year-old wood and 1-year-old wood cut back to a few buds.
  14. Viburnum – Remove dead wood to the ground.
  15. Weigela – Remove dead wood to the ground. Remove flowering wood back to unflowered laterals
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Modified: March 8, 2009 at 9:39 am UTC

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