Get It Growing: Its Your Last Chance To Prune Fertilize Many Plants This Year

Daniel Gill, Merrill, Thomas A.  |  7/28/2006 9:52:43 PM

GIG

Get It Growing News For 08/04/06

By Dan Gill
LSU AgCenter Horticulturist

August is a month when gardeners should think about two important aspects of landscape maintenance – fertilizing and pruning.

This month is the latest time in the year when we fertilize lawns, hardy shrubs and ground covers in the landscape.

It’s also the time to finish pruning many shrubs, cut back overgrown tropicals and trim some bedding plants. And it’s definitely the time stop pruning spring-flowering trees and shrubs.

You can use granular general-purpose fertilizers for most fertilizing jobs in the landscape. These fertilizers are relatively inexpensive and easy to use. They provide an immediate release of nutrients and then continue to feed for about six weeks to eight weeks thereafter.

If you feel you need to fertilize your lawn, shrubs or ground covers to encourage one last burst of growth, it’s important to do so now. Applications made this month will continue to feed until October – after which time it is not appropriate for hardy plants to continue to receive supplemental nutrients.

That’s because it is important for hardy plants in the landscape to slow their growth and prepare for the coming cold as we move into the winter. Late fertilizer applications, especially with nitrogen, can increase the possibility of cold damage, even to plants that normally would be hardy. This is especially true for us in Louisiana, since fall temperatures generally are warm-to-mild and do not give plants a strong signal to go dormant.

Granular fertilizers should be applied evenly to dry, freshly mowed turf and immediately watered in. Pay careful attention to the rate of application and spread the fertilizer evenly. This is difficult to do by hand, so use a fertilizer spreader to ensure even coverage.

Shrubs and ground covers may be fertilized by sprinkling the fertilizer in the bed where they are growing. You may also apply the fertilizer by sprinkling it around each plant. The size of the shrubs is a factor in determining the amount of fertilizer to use. Rates generally are higher for larger shrubs, but check package recommendations for specific amounts.

Keep this in mind, though. I am not necessarily saying you should go out and fertilize plants in your landscape now. If your lawn, shrubs and ground cover plantings look healthy and have grown well this summer, there probably is little indication that fertilizer is needed. If, on the other hand, there are some plantings you have been meaning to fertilize or that you feel would benefit from fertilization to boost their vigor, now is the time to do it – not later.

Pruning is another topic gardeners need to focus on at this time. Fall-, winter- and spring-flowering trees and shrubs (those that bloom from November through April) – such as sasanquas, camellias, azaleas, spireas, Indian hawthorns, cherries and Oriental magnolias, as well as summer-flowering gardenias and hydrangeas – already have set their flower buds for flowering next year. Extensively pruning or cutting back these plants from now on generally will diminish or eliminate their flower display in the coming season. It is OK to selectively remove specific shoots or branches to shape these plants, and you may be able to do that without affecting the flowering of the remaining growth. Just don’t get carried away!

Hedges, such as ligustrum, boxwood, photinia and viburnum, should be pruned by mid-September. Later pruning stimulates new growth during warm fall temperatures, and such new growth will not have time to harden off before winter. That can increase the chance of freeze damage.

Hybrid tea and grandiflora roses should be cut back fairly hard in late August or early September. Other types of everblooming roses also may be pruned as needed to shape, stimulate vigorous new growth, remove dead or diseased canes or control the size of the bush.

Our long growing season allows for the abundant growth of tropicals and tender perennials that are used as bedding plants in our gardens. In many cases they look somewhat overgrown now, but they will continue to grow and bloom until October or early November. Now is an excellent time to trim them back or even cut them back fairly hard so they will be more shapely, fuller and not so tall for the fall blooming period.

Popular bedding plants that benefit from trimming now include periwinkle, salvia, lantana, Mexican heather, blue daze, pentas, scaevola, purslane, begonia, impatiens and ornamental peppers. How far back you prune them depends on how overgrown you think yours are. Generally, plants are cut back about one-third to one-half their height, but I have cut many of the plants listed above back even more with good results.

I must admit this takes some determination and a strong will. Your plants certainly will not look their best immediately after the procedure of pruning. In many instances, though, it is well worth the down time. If some of these plants look overgrown now, think of how they will look by October.

Get It Growing is a weekly feature on home lawn and garden topics prepared by experts in the LSU AgCenter. For more information on such topics, contact your parish LSU AgCenter Extension office or visit our Web site at www.lsuagcenter.com. A wide range of publications and a variety of other resources are available.

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Contact: Dan Gill at (225) 578-2222 or dgill@agcenter.lsu.edu
Editor: Tom Merrill at (225) 578-2263 or tmerrill@agcenter.lsu.edu

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