help, i'm a newby! i'm afraid i'm going to have to completely re-do my patio of creeping thyme; it is only 4 years old, but despite my heroic efforts of weeding, i've not been able to stay ahead of the annual chickweed and now the perennial white clover ...ouch. the more of the weeds i take out the less thyme i have. is starting over my only option and if so, what should i use as a base? more sand? is preen my best friend here? and if so, when?