The Best Time to Prune
One of the most common questions heard in pruning class is, “when do I prune my azaleas, evergreen shrubs, or my crape myrtle”? It is somewhat confusing, and timing is important. How would our azaleas look in April if we cut off last year’s flower buds in February? I don’t know many people that plant azaleas with foliage in mind. On the other hand, the last thing we think about on boxwood or hollies are flowers which makes when we prune as important as where we make our cuts along each branch or stem. Remember, thou shalt not make flush cuts or leave stubs, even on the smallest branch. Let’s go over timing and see what plants in our area fall into each category.

Here it is: Plants that produce flower buds on last year’s wood should be pruned soon after the flowers have fallen. For instance, when your lilacs have finished flowering in April, prune them at that moment or in May. Conversely, plants that produce flower buds on new wood, or wood that has just been made in the spring should be pruned in winter, or early spring just prior to the beginning of that year’s growth. I think trying to differentiate between early spring and late winter might be confusing, so let’s just call them one in the same. Just concentrate your efforts between January and the first part of April in the Mid-Atlantic and you’ll be fine. NOTE: There are plants such as peach trees and some evergreen shrubs that can be damaged by sub-zero weather or severe temperature fluctuations. Try to hold off pruning until the threat of such weather has passed but before spring growth begins. All evergreen shrubs are pruned in winter, so that group is easy to remember. Does that make sense? This does not mean we cannot prune plants that flower on old wood such as lilac, forsythia or azalea in the winter. Just be aware that when you do, you will cut off flower buds that were produced during the last calendar year. We sometimes do this when we drastically renew or rejuvenate plants.

Renew=cutting the entire plant back to near or flat to the ground;
Rejuvenate=cutting a number of old canes back to near or flat to the ground while leaving younger more vivacious growth.

This way all new growth begins just after pruning, producing vast amounts of green, leafy material used for food production by the plant. You will only lose flowers for one season by pruning these plants during the dormant season, and then you can return to your regular pruning schedule during warmer weather, next year. Itís also good to remember that not all plants can withstand renewing or rejuvenating. For instance, azaleas, yews and many viburnums respond well to hard reduction pruning, while junipers are less tolerant. Therefore, when pruning junipers, be gentler, leaving lots of green leafy material for next yearís food production. To follow is a brief list of the major plants in our Regional zone (7) that should be pruned during the cold dormant season, before growth begins. Prune any others after flowers fall in spring or summer. Have fun and remember; leave no stubs and make no flush cuts!

PRUNE BEFORE ANY GROWTH BEGINS IN DORMANT SEASON

  • Rose of Sharon
  • Barberry, pigmy should be cut to 6-inches above ground
  • Butterfly bush, leave 6-12 inches above ground
  • Callicarpa, aka beauty berry, cut it hard
  • Caryopteris
  • Itea
  • Clethra
  • Hamamelis (witch-hazel), should not need much
  • Hydrangea, (Paniculata and Arborscens) must be done right
  • Japanese Kerria
  • Lagerstroemia, please let it gro, if you want it small, plant a smaller variety-remember, large variety crape myrtles become trees
  • Ligustrum, this includes privet.
  • Smoke tree
  • Japanese tree lilac, not to be confused with your common lilac shrub. Be sure to prune the shrub lilac in spring/summer as soon as flowers have fallen.
  • Roses (shrub varieties). We will have a more in-depth look at roses and a few other things later.
  • Spirea, prune Anthony Waterer and Douglasii in winter and bridal wreath, Thunbergii and Van Houtei in spring/summer after flowers have fallen. Some resources tell you to lump them all together and cut after flowering. This will assure flowering after pruning, next year.
  • Tamarix
  • Viburnum (berry bearing). We will also discuss this genus in greater detail, later.
  • Vitex
  • Prune your orchards during dormant season, but remeber to prune your stone fruits after Februarty 15th in the Mid-Atlantic
  • Prune your evergreen shrubs such as hollies, boxwood, yews, junipers, cedars
  • Deciduous ornamental trees and large shade trees should be done during the dormant season.

Should you find any particular plant confusing, let us know.

Copyright 2011 by Peter Deahl. All rights reserved.
 
Back to Articles
The Pruning School 16 Berkeley Court Sterling, Virginia 20165