The most effective way to keep a pebble path weed-free is to prevent the growth of weeds there in the first place. A barrier of permeable landscape fabric laid down between the layer of pebbles and the path's underlying base layer will prevent any weed seeds that germinate between the pebbles from taking root and growing. If you don't lay the fabric when the path is installed, you'll have to remove the gravel layer and replace it on top of the fabric.
Impermeable edging along the edges of the path also will help keep turf grass and other plants from growing into the gravel.
Natural Weed Killers
If weeds are already growing in the path, gardeners have several nontoxic natural methods to choose from that will help to control them, but each of the methods has drawbacks.
- Boiling water poured directly on weeds may be effective at killing them, but handling boiling water requires care to avoid spills and burns. This treatment will also only kill the weeds on which the water is poured and won't stop new ones from growing.
- Sprinkling coarse salt around the weeds may kill them, but it will also make the surrounding soil inhospitable to other plants. If the soil is sandy and rainfall is frequent, the toxic effect of the salt may spread beyond the path.
- White vinegar sprayed at full strength from a spray bottle directly on weeds will likely kill the weeds, but it will also kill grass and garden plants if you inadvertently spray them. Vinegar may also kill beneficial microorganisms in the soil.
Chemical Weed Killers
Chemical weed killers such as those containing glyphosate are very effective at eradicating weeds in garden paths, but they must be used carefully according to label instructions to avoid unintended consequences.
Mix and spray glyphosate herbicides directly on weed foliage with a spray bottle or hand sprayer. Be very careful not to get any overspray on plants you want to keep because the herbicide will kill any plant it touches. If necessary, protect plants you don't want to eliminate with a piece of cardboard. For the same reason, don't apply the herbicide on windy days. Don't apply just before a rain or before watering, because the water will wash the herbicide off the foliage and limit its effectiveness.
Measure out an appropriate amount of herbicide. (Follow directions on the herbicide level to determine the desired concentration of the final solution.) For instance, adding 2/3 ounce of a 41-percent glysophate herbicide to 1 gallon of water will result in a 1/2 percent glyphosate solution. Adding 13 ounces of herbicide to 1 gallon of water will result in a 10 percent solution.
Fill the sprayer with a gallon of water.
Add the herbicide to the water and mix thoroughly but carefully to avoid creating too much foam.