A reader asked me about controlling wild violets in her yard. I, too, have this problem not only in my lawn but in between the bricks in my walkway. So, I have a vested interest in learning about this as well.
Wild violets are perennial and have a fibrous root system which are difficult to completely remove by hand. They also have the ability to spread by rhizomes and seeds. In addition, the heart-shaped leaves often make it difficult to mow when they take over the lawn.
In my search on control options, I discovered that a simple household item might be all you need to rid yourself of this invasive beauty. Seems that household refined sugar might just be your cure ~ just not sure how it would work for a large lawn space. Take a look here.
Some other options:
1. Use a broadleaf herbicide such as Weed-B-Gon, active ingredient Triclopyr. This herbicide will leave grass alone because it is not a "broad leaf" plant. Benefit: it will save your turf and it takes a while to break down in the soil for longer control.
2. Use Round Up, active ingredient is Glyphosate. Problem: nondiscriminatory and will kill everything it touches. Benefit: it is systemic and will kill to the roots of the violet plants....and everything else it touches. You can reseed rather quickly after use of this chemical.
3. After a rain when the soil is softer and looser, get out there with a hand trowel and get those dang plants up including all the roots. Problem: you might not get all the roots and you will soon see more seedlings starting up from what is left in the ground. Benefit: you feel good about getting your hands dirty, you will see immediate results and you can immediately reseed the area.
Additional point: do not compost the violets because it will take quite a while to break down the seeds. A general composting tip: you need to get the plant/food material to a temp of somewhere around 120 degrees to degrade viable seeds. This does not usually happen in a backyard compost heap.
So, Note To Self: don't compost ANY weed that has already gone to seed.
Good luck with your choices. I might just be trying some this growing season also as my yard looks like the heart shaped leaves are winning out over my grass!