How can I get rid of clover mixed in and taking over my st. augustine? Soil is somwhat sandy.

Clover should die if you spray it with 20% vinegar on a hot, sunny day. Unfortunately, so will the St Augustine that the vinegar spray hits. If you can use cardboard to protect the grass and only spray the clover, that should work.

Clover WILL take over if you don't do anything.