Roundup herbicide, marketed by the Monsanto corporation, contains the active ingredient glysophate, which enters the leaves and kills plants on contact. Glysophate herbicides are sold under many brand names other than Roundup. It is toxic and regulations for home gardener use vary by state.

Japanese pampas grass, Omihachiman, Shiga Prefecture, Japan
credit: GYRO PHOTOGRAPHY/amanaimagesRF/amana images/Getty Images
Do not spray Roundup when it's windy.

Storing Roundup

Roundup is sold both in plastic spray bottles and in powders and liquids suitable for mixing into water to use in garden sprayers. To prevent Roundup from contaminating food, store it in a closed container.

Do not store Roundup in unlined steel or galvanized steel spray tanks or containers because it can produce highly combustible hydrogen gas that can flash or explode if ignited by a lit cigarette, a spark or an open flame. Use only aluminum, plastic, fiberglass and plastic-lined steel or stainless steel containers.

Mixing Roundup

Wear protective face shield and chemical resistant shoes, socks, long pants and long-sleeved shirts when mixing or applying Roundup.

If you use Roundup in a garden sprayer, mix the recommended amount in a larger container then add it to the sprayer tank. To prevent foaming and accidental contamination of a Roundup solution, do not use a mechanical agitator.

Applying Roundup

Roundup mist, droplets splatter or foam may stunt, discolor or kill desirable plants. Do not let Round drip, splash, drift or mist onto exposed roots, bark, stems, green shoots or foliage of fruit, flowers, ornamental shrubs or trees.

Do not spray it so heavily it drips off weeds and do not spray it in wind that can blow it onto ponds, streams, residential areas or the plants you want to keep.

Use a hooded spray nozzle to direct Roundup spray onto weeds and protect desirable plants. Adjust your sprayer so the lowest stream is at least 2 inches above the weeds you want to keep. Weeds should be 6 inches taller than good plants.

When applying Roundup take care not to inhale mist or spray or get it on your clothing.

Contamination Treatment

If Roundup gets on your skin or you breathe in the spray, it can irritate your eyes, skin or gastrointestinal tract, causing diarrhea or vomiting.

If you get Roundup in your eyes, rinse them gently for 15 to 20 minutes, removing contact lenses after the first five minutes. If you get it on your skin, wash gently for 15 minutes. If you inhale it, breathe fresh air.

If you swallow Roundup, do not induce vomiting. Drink water or milk to dilute it and call your doctor or the National Capital Poison Center at 1-800-222-1222, where an operator will connect you with a poison control expert in your area.

If a pet shows symptoms of poisoning for more than 24 hours, call a veterinarian.

After Use

To prevent corrosion of sprayer after use, flush parts with water. After application, wash your hands before you use the toilet, chew gum, eat, drink or smoke.

To prevent Roundup from getting transferred to desirable plants, keep pets and people off the treated area until the Roundup has dried. Stay away from treated areas for at least 12 hours.

If Roundup gets inside your clothing, remove and wash it immediate and dress in clean clothing. Wash the clothes you wore while working with Roundup separately from other laundry in hot water and detergent. Throw out pieces of clothing that have been drenched in Roundup.

Wait at least 30 days before planting fruits or vegetables on soil treated with Roundup. Do not harvest nearby fruits or vegetables for a week after applying Roundup on weeds.