It's spring: what can I prune

Jack Phillips
Adams County Master Gardener

While you are waiting to get started with your early summer gardening, a good early spring project to undertake is pruning certain of the flowering trees, shrubs and other perennials in your yard and garden. Pruning, at the proper time, keeps your trees, shrubs and bushes in shape, encourages new growth and invigorates the amount and quality of your bloom.

The general rule is that you only prune the early spring and early summer bloomers after they bloom, which means very late spring or mid-summer. On the other hand, the late summer and early fall bloomers are best pruned during their dormant stage which is late winter and early spring. There is at least one exception to this rule. For example, while it is true that early spring bloomers set their bud bloom the fall before, it is often easier to prune these plants for shape while they are bare, so you can more clearly see the structure of the plant and before the branches get masked by the leaf growth. Pruning them at this time of year would generally mean losing some or much of the bloom which would otherwise appear later this year. But, when shaping of the plant or shrub is cosmetically critical, the gardener can ignore the general rule just that once. He or she must just understand and accept the consequences. Following are some trees and shrubs that are best pruned immediately after they finish their spring or early summer bloom:

  • Azalea (Rhododendron species)
  • Beautybush (Kolkwitzia amabilis)
  • Bridal Wreath Spirea (Spirea x vanhouttel)
  • Flowering Crabapple (Malus species and cultivars)
  • Forsythia (forsythia x intermedia)
  • Hawthorne (Crataegus species and cultivars)
  • Hydrangea, Bigleaf (Hydrangea macrophylia)
  • Lilac (Syringa vulgaris)
  • Magnolia (Magnolia species and cultivars)
  • Mockorange (Philadelphus coronarius)
  • Mountain Laurel (Kalmia latifolia)
  • Rhododendron (Rhododendron species)
  • Serviceberry (Amelanchier x grandiflora)
  • Slender Deutzia (deutzia gracilis)
  • Weigela (Weigela florida)

Early spring pruning is for those trees and shrubs which set their bloom on new growth and is best done when they are still dormant. While it is our view that serious large-tree pruning is an art best left to the tree professionals, with respect to small decorative trees, the average gardener can certainly deal with the need to remove broken, dead and diseased branches, as well as any sucker sprouts which are easily reached from the ground or with a medium height ladder. With pruning loppers and pruning shears, or with a curved tree saw when required, make those cuts just outside the flare or branch "collar." The collar is the slightly swollen part of the base of the branch. Avoid top pruning or giving the tree a sheared look. And by all means, avoid using pruning paints or wound dressing on the open cut, as they tend to harbor disease organisms.

Pruning landscape shrubs and bushes should be well within the capability of most home gardeners. Much of this pruning can and should be done in early spring. Following are some of the more common landscape shrubs and trees that fall into that category:

  • Bradford Pear (Pyrus calleryana)
  • Butterfly Bush (Buddleia Davidii)
  • Crape Myrtle (Lagerstroemia indica)
  • Flowering Dogwood (Cornus florida)
  • Flowering Plum (Prunus blireana)
  • Glossy Abelia (Abelia x grandiflora)
  • Golden Rain Tree (Koelreuteria paniculata)
  • Honeysuckle (Lonicera fragrantissiam)
  • Hydrangea, Peegee (Hydrangea paniculata "Grandiflora")
  • Potentilla (Potentilla fruticosa)
  • Redbud (Cercis canadensis)
  • Spirea (except Bridal Wreath) (Spirea japonica)
  • Wisteria (Wistera species)

If you read both of the above lists carefully, you will note that the hydrangea shrub appears on both lists. How can this be, you ask? This is not an error. The Big Leaf Hydrangea is one that sets its bloom the fall before, so an early spring pruning would ruin this seasonís bloom. The Peegee Hydrangea, on the other hand, sets its blooms on new growth, so early spring pruning will not adversely affect its bloom later that season.

Basic pruning starts with thinning out the older shrubs and bushes, and this is best done by cutting out the older canes all the way to the ground. A general rule is to remove one-third of the oldest canes each year.

The list of which shrubs and plants either need or can tolerate a more severe pruning, or even a full "cut-down," and still survive with a flourish, is a subject for yet another article. But for example, I commonly have good results when I cut my butterfly bushes back to about three feet above the ground and my sedum and certain of my spirea, to the ground. Some clematis can take rather severe pruning, but there are three different categories of clematis, so "when" and "how much" depends into which category your particular clematis falls.

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