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Gardening with Rick Weatherford
Invaders in your garden
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    “A weed is just a wildflower out of place,” botanists often say. What they mean, of course, is that all plants have a certain beauty, they just need to be in the right place.  Anyone who has tried native gardening knows that what they once considered weeds may now have a place of prominence in their garden.
    But not all weeds are created equal.  There are a group of plants called invasive species that don’t have any place in our gardens.  Invasive plant species are usually exotic, or not native, and cause economic or environmental harm, or harm to human health.  Once they get a foothold in your garden, it can be very hard to get rid of them.  An excellent example of an invasive species in Georgia is the kudzu vine.  Brought to the U.S. originally in 1876 for the Philadelphia Centennial Exposition as an ornamental, it was planted widely throughout the southeast for forage and soil erosion control.  Kudzu’s fast growing nature, up to 12 inches a day, and its ability to cover all plants it surrounds—robbing them of sunlight and eventually killing them—caused  it to be declared a weed by the U.S. Department of Agriculture in 1972.  Today it can be seen covering large sections of forests along virtually any highway or interstate in the southeast.
    Not all exotic plants are invasive, however.  What separates an invasive plant from a simple exotic plant is its “aggressive” growth habit and its ability to crowd out other plants and take over habitats. These plants damage farmland, commercial timber forests, and sensitive ecologies, and can ruin your home garden.
    Not all of the 23 invasive species identified by the Georgia Invasive Species Task Force are a problem in this area, but there are some that you may be surprised to learn are invasive. Silk tree (mimosa), tree of heaven, Chinaberry tree, Chinese privet, wisteria, autumn olive, and Japanese honeysuckle are the most common invasive plants in our area and many are still being planted in gardens as ornamentals. Most of these were originally brought from Asia. Once established, they are difficult to remove.
    What do you do if you have an invasive species (or other plant) you would like to remove?  For large infestations in forests and farms the prescription usually calls for wide-area herbicide spraying to remove the problem.  There is a vast array of herbicides that have been developed for just such a purpose.  But for the gardener this method is cost prohibitive and it is likely that the invasive plant is mixed among other desirable plants that could also be easily killed.  If you don’t want to use chemicals, as is the case for many gardeners and landowners, the answer is a bit of elbow grease and a lot of persistence.
    Start with the elbow grease: identify the plants on your land or in your garden that you would like to remove and pull them up by the roots.  If they’re too big to pull, cut the stem 1-2 inches from the ground.  Because a lot of these plants will grow suckers or new shoots from the cut stump, I recommend that you apply an herbicide such as glyphosate (Roundup©) full strength or some other stump killing herbicide immediately.  If you go for longer than a week between cutting the stem and applying the herbicide, you will want to cut another one-half to one inch off the stump to reopen the pores to the roots.  Next, remove all of the trimmings either by burning (if applicable and legal in your area) or taking to a landfill. This is especially important if the plant had seeded prior to removal since you do not want to take the chance that seeds get back into your garden.  Clearing by cutting can be done any time of the year but is best for deciduous plants, such as silk tree, to be done during the growing season from March to October to allow any herbicide you might use to have its effects on the stump.
    The next step is the persistence step:  these plants are invasive precisely because they have the ability to hang on in the habitats where they become established. They do this either by re-growing from still living roots or by having a large disbursement of seeds in the soil.  To get rid of these you will need to inspect your garden every 1-3 months for the first year after your initial removal and either pull the sprouts by hand or spray them with a foliar herbicide such as glyphosate (Roundup©).  Do this until you no longer find any new sprouts.  Once this step is complete, you will want to survey your garden and eradicate any new plants you may find at least once a year.
    For more information on invasive plants in Georgia, visit the Georgia Invasive Species Task Force Web site at
    Rick Weatherford worked as a land manager for the Army at Fort Stewart for eight years before deciding to return to graduate school to get his master's degree in public administration.  He is currently working at the GSU Botanical Garden as a graduate assistant and hopes to go into land conservation upon completion of his degree in July of 2008.
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