Sidewalk cracks are necessary for the expansion of the concrete slabs. When the sidewalk’s surface heats and cools, it expands. If the sidewalk had no room to expand, it would heave and break. However, each spring, weeds try to grow in the sidewalk cracks. The best way to kill these weeds is to spray them with an herbicide. After the initial application, the weeds dry up and die. Then, either pull the dead weed out of the crack or let it decompose.
Purchase a weed killer. If you know the type of weed growing in your sidewalks cracks, read the label to find out if that specific killer attacks that weed. Treat unknown weeds with a broad-range herbicide.
Read your local area weather report. An ideal day for treatment has little to no wind and no rain predicted for at least six hours. Treated areas are safe to walk on once they are dry.
Spray the weed killer directly onto the surface of the weed leaves. Soak the leaves but do not create run-off.
Wait at least two days before pulling the weed from the sidewalk crack to allow the killer to penetrate the weed roots.