I have a customer who wants us to do some weeding of their plant beds. We've done it twice already without laying any poly or spraying, and they came back almost as fast as we pulled them. Any ideas on what we should do to ensure that they don't come back? I was thinking that we'd 1. Pull them 2. Spray with chemicals 3. lay some sort of matting over them 4. re-mulch The customer wants me to gurantee that they won't come back.