Death Signals

Effective on 200 weed varieties for up to four months, Roundup is a glyphosate-based product that starves plants by blocking an essential growth enzyme. Signs that weeds are dying may be seen within several hours to several days. The first indicator is wilting or withering. Leaves may turn yellow, curl, fall off or turn brown at the tips. Eventually the entire plant browns. Visible results aren’t as fast in drought conditions or cold weather; it can take up to a month before telltale signs appear.

Mortal Combat

One gallon of ready-to-use spray covers 300 feet, or approximately 1,000 weeds. Roundup enters the plant through living green tissue. Cover as much foliage as possible, thoroughly saturating but not to the dripping point. Roundup travels to the roots in a couple of days, so even if you can't tell that it's working, it's attacking the weed from the inside. Once the treated plants have dried, the area is safe for you, your pets and children.

Tougher Enemies

Ridding your landscape of plants with thick, waxy leaves, such as poison ivy(Toxicodendron radicans), found in U.S. Department of Agriculture plant hardiness zones 4 to 10, or climbers like invasive kudzu (Pueraria Montana) in USDA zones 5 to 10, may take more than one application. Use the Roundup formulation designed for tenacious weeds. Lop off bark-covered branches or vines and apply Roundup to the cut ends, allowing the product to penetrate. If you haven’t seen results in a month, reapply. Spray any new growth around the original weeds every three to four weeks.

Protect Desirable Plants

If you accidentally spray Roundup on a plant you want to keep, immediately rinse it with water. The product is rainproof after 10 minutes, so you have limited time to react. Even then, it may be too late, depending on how heavily the plant was sprayed. To avoid harmful drift, apply Roundup on a calm day and shield desirable plants with a piece of plastic or cardboard.