The answer is-- it depends. It depends on the weed and what's around it.
For broadleaf weeds in turf, something like Trimec works well.
For grassy weeds in groundcovers or flowerbeds, Poast and Fusilade work.
For nutsedge anywhere, Manage or Sedgehammer work.
For tough weeds like bermudagrass or bindweed, your best bet is Round-up, if there is nothing else growing nearby. You can make a protective collar of cardboard or plastic to protect desirables nearby.
ALL of these are safe in the garden as long as you follow the directions, follow the directions, follow the directions.
Also, when in doubt take a large sample to your local independent nursery- like Armstrong
