We have a few lovely large palmettos; however, we also have little palmettos growing everywhere. We have tried Round-up and gasoline to kill the weeds.
How to Kill Palmetto Palm Weeds
Certified GKH Gardening Expert
They are often resistant to Round-up, and since this is toxic to lawns, your best bet is to dig them out before they become to established. It may also help if you applied a pre-emergent herbicide, for instance "RONSTAR' pellets, to prevent further germination of seeds. It is safe to use in most lawn areas and lasts for about six months. Use the pre-emergent herbicide in mid-February. For additional info, here is an article that you may find helpful: https://www.gardeningknowhow.com/ornamental/trees/tgen/weed-trees.htm