Regardless of what it is…
If you only have a few small patches - you could start with a shovel and try and remove the entire underground part of the plant.
It is broadleaf, so choose from any of the broadleaf weed products that are labeled as suitable for your lawn grass type/mix (the grasses you don't want damaged).
Don't chose glyphosate as it will kill everything.
Always read the labels and follow the directions!
Edited by Grae, 09 August 2018 - 08:23 PM.