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Tops and Bottoms

When moving trees and shrubs, if you interfere with one, leave the other alone

When you’re transplanting a tree or shrub, leave the branches alone. Once upon a time, gardening wisdom advised pruning back the branches to compensate for the roots lost when the plant was dug. I have been convinced for some time that this practice had been laid to rest, until I recently heard a garden expert on the radio recommend it to a listener who had called for advice.
    The science of horticulture has discredited this practice, whether the plant is dug with a root ball or bare-rooted. Here’s why: The hormones that stimulate new roots to grow are produced in the buds on the branches. If you prune away branches, you are reducing the amount of natural-occurring rooting hormones, manufactured by the buds at the ends of the branches, that can be trans-located to the roots.

Look Inside the Pot

When purchasing woody plants grown in containers, remove the container from around the root balls and examine the roots. Roots that are alive are creamy white to yellow. On the other hand, roots that are brown and turning black are a clear indication that the plant was not properly stored and will most likely not survive being transplanted. We have had a mild winter, but the plant could have been shipped from somewhere the winter was much colder.

    If your intent is to control the size of the tree or shrub, first allow the plant to become well established, which takes about a year, before pruning the top. The reason is that the roots produce the gibberrellins and cytokinins essential for stems to grow.
    To be successful in transplanting trees and shrubs, don’t prune the top, and don’t prune the roots at the same time that you are pruning the top.
    This rule does not apply when planting trees or shrubs that have been grown in containers. That’s because all of the plant’s roots are within in the container it grew in.
    When transplanting container-grown plants, make certain that the plants are not root-bound. A root-bound plant is easy to identify by removing the container and examining the root ball. If the root mass is so dense that you cannot see the growing medium in which it is growing, consider the plant root-bound. Should you purchase that plant, take a sharp knife or pruning shears and cut those roots starting from the top to the bottom of the root ball in four or five locations before planting. Otherwise, the plant will not establish and is likely to die in three to five years. If you do cut the roots of a root-bound plant, do not prune the top until the plant is established.

Ask Dr. Gouin your questions at [email protected]. All questions will appear in Bay Weekly. Please include your name and address.