Spectracide Weed & Grass Killer Instructions

Updated February 21, 2017

Sepctracide Weed and Grass Killer is a broad-spectrum herbicide designed to kill unwanted perennial and annual plants wherever they creep up. Broad-spectrum herbicide will kill any herbaceous plants that it comes in contact with. To avoid accidents, it is important to apply weed killer carefully. Stray herbicide spray or over-application can kill your desirable plants as well as the weeds you want to get rid of. The safest time to spray is when the weather is over 15.6 degrees Celsius, the weeds are actively growing, there is no wind and there is no rainfall forecast for 48 hours.

Mix the sprayer with water if using the concentrate form with a hose-end or hand-held sprayer. To kill young, newly sprouted weeds, mix 3 fluid oz. (6 tbsp) per gallon of water, per 300 square feet. For long-established weeds, mix 5 fluid oz. (10 tbsp) per gallon of water, per 300 square feet. For hard-to-kill perennial weeds, mix 7 fluid oz. (14 tbsp) per gallon of water, per 300 square feet. Do not exceed 7 fluid oz. per gallon in a single application. Skip to step two if you are not using a concentrate.

Cover any desirable plants near the treatment area with water from a hose. Then cover them with a sheet of plastic to protect them from any accidental overspray.

Spray the plants. Coat all of the weed's leaves generously, but stop just before the point of run-off. Follow all appropriate directions for your hose-end or hand-held sprayer.

Wait for the weeds to die. Most weeds will begin to yellow and brown within 24 hours. They should die within two weeks. Do not dig the weeds until after seven days, when it is clear that they are dead. If the weeds are not dead after two weeks, spot treat the remaining weeds. Do not spray the weeds more than twice in one season.


Do not use Spectracide to spot treat weeds in lawns, or around edible plants. Wear long clothing and gardening gloves when spraying the weeds. Wash both your clothing and the gloves alone right after you are finished. Wait seven days before replanting the area with grass, wait one day before replanting flowers, trees or shrubs, if the weeds are clearly dead. Do not water the treated area for at least 24 hours. If you accidentally get overspray onto your desirable plants, wash it off with water immediately.

Things You'll Need

  • Hose-end sprayer
  • Hand-held sprayer
  • Plastic sheeting
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About the Author

Based in Houston, Texas, Meg Butler is a professional farmer, house flipper and landscaper. When not busy learning about homes and appliances she's sharing that knowledge. Butler began blogging, editing and writing in 2000. Her work has appered in the "Houston Press" and several other publications. She has an A.A. in journalism and a B.A. in history from New York University.