Roundup is the brand name for a line of weed-killing products sold at garden centers and hardware stores. Roundup is available in ready-to-use spray formulations and as a concentrate that must be mixed with water before applying for weed control. The products have a long shelf life, typically more than a year, and each Roundup product has an expiration date stamped on the label. If you are unsure about the age of the product, or if the label has worn away, and you want to assess the product's quality, apply it to a test area on your lawn.
Turn the Roundup packaging over in your hands to inspect the back label and check the expiration date. If the date has passed, it may be more effective to dispose of the product and buy fresh Roundup. Contact your local waste disposal authority for proper disposal instructions.
Apply Roundup to a test area in the garden or on lawn weeds, following the recommendation for your particular Roundup product. For example, apply an even spray of product from a ready-to-use trigger bottle on an area of ground weeds. Do not use Roundup in high wind, immediately before or after it rains, or in extremely cold or hot weather, as these factors reduce the effectiveness of the product.
Pull up weeds in the treated area after seven days to check for evidence of drying, browning or curling, which are all signs the Roundup is working as designed. If after two weeks there is no evidence the leaves of the weeds are dying, properly dispose of the Roundup product and replace it with fresh Roundup.
Pull weeds again after three weeks to check the root structure. Roundup kills weeds through absorption into the leaves, then works its way into the root structure to kill the plant. This process takes three to four weeks for maximum effectiveness.