Weeds that grow in cracks between pavers are a common nuisance. The best solution is preventive: Spread a layer of landscape fabric under the pavers when you install them. The fabric prevents weeds from rooting in deeply. You can also kill weeds as they sprout. Various herbicides are available. Some, such as glyphosate (Roundup), kill the weeds that are present when the herbicide is sprayed but leave no residue. Others remain active in the soil after you apply them, preventing weeds from germinating for several months or more. Use caution with herbicides, and follow label directions. If you prefer to avoid chemical herbicides, carefully flame the weeds with a propane weed torch, or pour boiling water on the weeds to kill them.