Dig out as much of the weed as possible before cleaning out any remaining dirt or debris from the crack with water and a stiff wire brush. Allow the concrete to dry before continuing.
Aside from being aesthetically unpleasant, weeds poking through sidewalks pose several threats to your asphalt, and family. If left unattended, the weeds will thrive, grow and can eventually create severe concrete deformations and heaving, which is only mended by tearing out the slab. Larger weeds are also tripping hazards, and will continue to reemerge after countless applications of herbicides. Manually eradicate the weeds before prepping the cracks and applying a quick-drying joint sealant.
Pack the crack tightly with sand before filling it with a quick-drying joint sealant. Cut the sealant’s tip and insert it directly into the crack. Squeeze the product into the crack and overfill to allow for the shrinkage that occurs after drying.
Spray the weeds with a 5-percent acetic household vinegar. Concentrate the spray on the weeds, reapplying several times over a two- to three-day period or until the weed tops and roots are dead.
Allow the crack sealer to dry for 12 to 24 hours, or according to the package directions. Examine the crack and reapply, if necessary, to fill any remaining small holes or voids in the hardened product.
You will quickly recognize that various weeds have their favorite seasons, and are vulnerable to different control methods. The damp spring might be best suited to plucking weeds by hand, while during the dry months of late summer, chemical herbicides might be the better strategy.
Some grasses and weeds thrive in the heat. Crabgrass, for instance, is a warm-season annual grass that thrives in driveway and patio cracks. Its seeds are very tiny and can penetrate the smallest cracks. Quackgrass is even more diabolical because it is a perennial weed that can survive even if just small pieces of root remain beneath the slab. If the exposed portion of the grass is removed, a new shoot will pop up in no time at all.
Before Getting Started
The reality is that pavement weed control is an ongoing landscaping maintenance task for homeowners, but the work is easier if you have a variety of workable strategies to choose from.
Grasses and weeds growing out of pavement cracks in sidewalks, driveways, and patios is a common annoyance. Sometimes it seems as though these unwanted plants grow even better in tiny pavement crevices than they do in the lawn and garden. This defies all logic since pavement surfaces are brutally hot and dry places where you might think that nothing could survive. But not only do these tenacious grasses and weeds survive, they alsoseem to positively thrive in this no man’s land of blistering hot pavement.
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Kathleen Connolly has been an advanced master gardener and accredited organic lawn care professional for over 30 years. She specializes in lawn care, horticulture, and landscape design. Kathleen earned a Master's Degree in Landscape Planning and Design and Sustainable Land Use Planning and Design.