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Index : Pests
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- 25. Roundup Weed Killer Popular with Gardeners - Top
- One of the most popular weed killers for home garden use is a material called Roundup. Sold under various trade names including; Roundup, Kleenup and Weed and Grass Killer, the common chemical name of this product is Glyphosate, which will always appear as the active ingredient on the product label. Roundup is a systemic herbicide. This means that it is absorbed into the plant and is carried internally through the plant. Because of it's systemic character, Roundup is applied to green leaves and green stem tissue. It is absorbed and moves through the entire plant, killing it, roots and all. This is especially beneficial in controlling perennial weeds. When the roots are dead, the weed will not regrow.
Roundup is most effective on perennials including weedy grasses such as wild Bermuda grass and broadleaf weeds like plantain. It is "nonselective", meaning it will kill virtually any green herbaceous plant it comes in contact with. It can be used to spot treat weeds in the lawn, edge trees, control weeds in shrub beds, and eradicate weeds that pop up through patio blocks and gravel driveways.
Unlike many weed killers, Roundup has no effect on the soil and is safe to use to eradicate weeds prior to sodding a new lawn or planting a landscape bed. Applications of Roundup must be made carefully. Any green plant tissue will absorb this product, not only leaves but also green twigs and trunks, like those of Palo Verde trees. Sprays must be directed to avoid contact with desirable plants. The best time to spray is in the early morning when the air is calm. When spraying in "too close for comfort situations", use a piece of cardboard to shield desirable plants from the weeds you intend to spray. Tall weeds in a shrubbery bed can be bent over and sprayed on the ground.
After applying Roundup, give it time to work! Because it is a systemic it must be absorbed by the leaves and moved down within the plant to it's roots. All this takes time, usually about 7 to 10 days. Plants will begin to yellow up and then die. Do not pull or hoe the weeds out until they are completely dead. If weeds are emoved before the chemical can move into the roots, they will just regrow.
One final precaution, Roundup, like all other pesticides should always be used according to label directions. Use the dosage recommended. The adage "if a little is good, a lot is better" does not apply with pesticides including Roundup. Overdosing will cause the tops of weeds to die before the Roundup is moved into the roots. Roundup (glyphosate) is available for purchase in several formulations of varying concentrations. The most concentrated forms contain 41% glyphosate, while the least concentrated premixed and ready to use products contain only .5%. If you are planning to use the product frequently, a more concentrated form would be the best buy even though the initial cost is more.
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Written by John Begeman, College of Agriculture and Life Sciences, the University of Arizona, 520-626-5161.
Material originally appeared in Arizona Daily Star gardening column, on August 4, 1996
- Updated: August 4, 1996
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