llet me see if i can give you some help or at least some encouragement as i was in your situation last spring...i live in fl. and have st. augustine grass: oxalis occupied probably 75% of 1000 sq. ft. of my backyard...i pulled all visible weeds knowing that some roots were left behind as well as the seeds...this at least gave the grass room to start spreading...sprayed a pre-emergent(at this point, i had already pulled the emerged oxalis)...i did have to solarize about 200 sq.ft. and plug as there was no grass at all in that spot...this was very time consuming...my yard looks the best it has ever looked...be sure and check the herbicide for use on your particular grass type if you should use one...good luck...bz

thanks so much, bz! yes, time for me to take an intellectual approach to the problem :)