You DON'T NEED TO USE ROUNDUP!!! That stuff is so noxious. Use straight agricultural strength vinegar (20%--the kitchen stuff is 5% and will turn stuff brown, but not necessarily kill it) and spray it on the weeds. Try a test area first, and be prepared to dig stuff out as it dies; vinegar doesn't stick around in the soil to keep killing things.

Visit The Dirt Doctor to get a lot more organic information. The site has answers for just about anything you can think of. It's based in Texas, US, so some translation of terms may be necessary. You can join the group and write to the forum and ask your questions. (I've even set it up to display in its own window, so you won't lose your place at Mudcat! Add it to your favorites!)

SRS