No, It only works to kill seeds while germinating, won't work on the weeds themselves. Active life is 3 months for "flower" preen and 1 month for "vegatable" preen, so effect will be over before spring gets here. Can't think of the righht name of the weed you're talking about...light green ,3-leafed "clover" looking, small yellow flowers!? We've got it here also, call it "sour grass". Don't know why....doesn't look like grass? Anyway ,preen would be best used, in your case, early spring, before anything germinates....but....it will stop those Poppies,too!...Arlyn
