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Prune plants for health and to promote growth

By Bob Hearle

Several of you have contacted me to ask about your soil test results. I will address than in the next column.

This week's topic is pruning, often a controversial subject here in South Carolina. Hopefully, last season you cleaned and oiled your pruners and shears and they are ready to go. If not, now is the time to remove the rust and apply some lubricant. Remember that during the year as you prune diseased branches you need to thoroughly clean the shears with a chlorine detergent before moving to another plant. If you do not, there is a high probability you will spread the disease.

What should be pruned and when? Does it matter? This is easy to answer: It matters.

Before discussing what to prune, and when, we need to discuss why. Pruning should be used to remove damaged branches, but never the header (leader) branch unless damaged by wind or snow/ice. Remove other branches to rejuvenate the plant or give it a particular shape.

Branches that grow parallel to the leader are called suckers, and should be removed. Branches arising out of the top of the root ball (crown) should also be removed. It is easier to do this before the leaves appear, but be cautious. Summer flowering shrubs are best pruned before spring growth begins. They will produce their flowers on the new growth.

Some examples, but not a complete list, would include:

  • Butterfly bush
  • Camellia
  • Crape myrtle
  • Many rose varieties
  • Japanese bayberry
  • Japanese spirea
  • Mimosa
  • Nandina
  • Rose of Sharon
  • Plants that flower in the spring should only be pruned after the flowers are gone because they produce their flowers from last year's (old) growth. A partial list, but certainly not an exhaustive one, includes:

  • Azalea
  • Hydrangea
  • Bradford pear
  • Climbing roses
  • Crabapple
  • Dogwood
  • Forsythia
  • Gardenia
  • Indian hawthorne
  • Japanese pieris
  • Lilac
  • Redbud
  • Pyracantha
  • Wisteria

    Pruning for rejuvenation offers two approaches. For multi-stemmed plants such as azelea, you can prune branches (or the entire plant) back to within 6 to 12 inches of the ground. Or decide to do a three-year plan and cut one third of the plant back each year.

    Cuts to remove a branch should be made above a node, as this is where the new branch will form. Complete branch removal should be close to the larger stem from which it originates. Pruning evergreens is a bit different, and simply achieved by cutting the "candles" (new growth) as far back as desired. You can control growth as well as shape using this technique.

    Specific questions about pruning a particular plant are best addressed to your horticulture or garden center. They know their stock and how to care for it.

    Remember that the branches contain leaves that are rich in chlorophyll, and it is this chlorophyll that produces all the energy a plant needs to perform its many tasks. Removing a branch removes the energy source. Imagine if someone took away your food. What energy would remain for you to perform your tasks?

    Chlorophyll in the presence of sunlight, carbon dioxide and water produces sugar and oxygen. (6CO2 + 6H2O + sunlight/chlorophyll ---> C6H12O6 + 6O2) The sugars are then moved around to the parts of the plant needing them for root and bud growth, flower and seed production, and general plant maintenance.

    In the fall, when the temperature drops and the hours of sunlight diminish, the plant uses chemicals in the leaves to convert the chlorophyll into other nutrients and produces the yellows, reds and oranges that we love so much. The plant then drops the leaves until new ones are produced in the spring.

    If you come from the Northeast or Midwest, be thankful. Back there your garden would be under several inches (maybe feet) of snow and frozen solid.

    Continue to check your seeds for moisture and growth, have that soil analyzed and read those catalogs. Think spring and before long it will be here, and you should be ready to burst from the starting gate and enjoy the rewards of your preparation.

    Bob Hearle is a certified master gardener who lives and gardens at Pawleys Island.

    Previous columns

  • Seed propagation
  • Introduction / Soil tests

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