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Get it Growing For 12/12/08
By Dan Gill
LSU AgCenter Horticulturist
Now is an excellent time to evaluate your landscape for any pruning that needs to be done, since many plants can be pruned now through February.
Plants that may be pruned during the winter and early spring include most woody plants such as trees and shrubs, hedges, screens and foundation plantings that are not grown for their flowers. Both evergreen and deciduous plants—those that lose their leaves during the winter – may be pruned.
You should, however, avoid extensive pruning of spring-flowering trees and shrubs (those that bloom from January through April), such as Japanese magnolia, silver bell, parsley hawthorn, Taiwan flowering cherry, quince, azalea, Indian hawthorn, deutzia, philadelphus, spirea, banana shrub, wisteria and camellia. They have already set their flower buds, and any pruning done before they bloom will reduce the floral display these plants will produce.
Summer-flowering trees and shrubs such as crape myrtle, vitex, althea and abelia may be pruned during winter. They will set flower buds on new growth they produce next spring and summer.
Gardenia, hydrangea, some old garden roses, ramblers and some climbing roses are in a category of their own. They bloom in early summer, but they have already produced their flower buds or flowering shoots for next year. Extensive pruning done from now until they bloom next will greatly reduce or eliminate flowering then. Prune these plants in mid-summer soon after they have finished blooming to avoid problems.
How to prune
Pruning is often neglected because gardeners are not exactly sure what to do. There is a great deal of confusion about how to prune, when to do it and even why pruning is done.
The only way to gain confidence in pruning is to do it. Practice makes perfect, as that saying goes. The first step to gaining confidence is to ask, and fully answer, two questions before pruning begins.
First, why, specifically, do you feel the plant needs to be pruned? What specific goal do you want to accomplish or what problem do you need to correct? Some plants won’t grow just the way we want them to, and so they need to be shaped. Some plants will grow larger than we anticipated and need to be pruned regularly to control their size. Dead branches may be pruned for the health of the plant. Sometimes a tree has branches that are too low and cause problems or obstruct views. The list goes on. If you can’t come up with a good reason to prune a plant, leave it alone.
Second, decide how the plant must be pruned to accomplish your specific goal. Study the plant carefully and decide what precisely needs to be done before you begin. Most gardeners feel they don’t know what they’re doing and are afraid of damaging or killing the plants they prune. Each plant is different; the desires and needs of each gardener are different; and each situation is unique. But if you have identified why you need to prune and what you’re trying to accomplish, the task before you will be come clearer.
To accomplish your goals, you should become familiar with the basic pruning techniques we use to shape and control plants.
Heading back involves shortening shoots or branches and stimulates growth and branching. Heading back is often used to control a plant’s size, encourage fullness, rejuvenate older plants and maintain specific shapes as in topiary and espalier. Often overused by gardeners, careless heading back can destroy the form of a plant in situations where the natural shape is desirable.
Shearing is a specialized type of pruning done with a pruning tool called shears, which look like large scissors (there are also gas- and electric-powered shears). This technique – a variation on heading back – is used to create geometric shapes, espalier or topiary that is common in formal landscape designs. Shearing should not be used for general pruning such as controlling size. The result will be clipped, formal shapes that require a lot of work to maintain.
Thinning out removes shoots or branches at their point of origin, either back to a branch fork or back to the main trunk. Thinning cuts can control the size and shape of a plant while doing a better job of maintaining the plant’s natural shape. They are also used for removing branches that are too low on trees. Thinning cuts do not stimulate growth and often work more with the plant’s natural growth patterns to correct problems.
Here are some basic recommendations regarding pruning.
-- Prune only if necessary and use proper and sharp pruning tools. Generally, it is better to prune lightly and regularly than occasionally to prune severely.
-- Do not prune plants when they are under stress, such as in extremely hot, dry weather.
-- Do not prune shrubs and hedges late in the year between September and December; the new growth stimulated will not have time to harden off before freezes. If needed, extensive pruning should be done to spring-flowering trees and shrubs soon after they finish flowering. Prune most summer-flowering trees and shrubs in February. Remove dead growth anytime.
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Contact: Dan Gill at (225) 578-2222 or dgill@agcenter.lsu.edu
Editor: Rick Bogren at (225) 578-5839 or rbogren@agcenter.lsu.edu