Viney lawn weeds like creeping charlie can quickly take over a lawn that is thin or overly moist and shady. Viney lawn weeds may be so prevalent that you find you have more weed than grass in your lawn. Roundup is a useful herbicide for killing pernicious viney lawn weed infestations, but in order for the spray to be optimally effective, it must be sprayed on viney lawn weeds while they are actively growing.
Mow the lawn and the viney lawn weed as close to the ground as possible.
Wait for the viney lawn weeds to grow 4 to 6 inches. Perennial weeds like viney lawn weeds must be actively growing to transfer an herbicide like Roundup to their extensive root systems.
Mix the Roundup with water, according to the manufacturer's instructions, if necessary. However, most Roundup products for home use come premixed in easy-to-use spray bottles.
Spray the product on the viney lawn weeds. The spray should coat all of the plant's tissue, but should not be applied so heavily that the product runs off. Spray early in the morning or late in the afternoon when the sun is at its weakest.
Re-spray plants at 7 to 10 day intervals as needed (if the weed shows no sign of decline during this period). Re-spray any new growth as soon as it crops up.