04-08-2007, 04:39 PM
I would use Round-up and then if you didn't mind dealing with the mess, you could use a pressure washer to gouge out the crack so you could patch it with filler. If you just use the pressure washer you may leave living roots behind that may try to grow back through your patch material. It's amazing how much force plants can exert - I once saw weeds pushing up on couple of inches of asphalt after someone had put it down without completely killing the weeds that grew there beforehand. Round-up will kill the weeds right down to the roots.