Violets love cool moist conditions, acid soil and lots of organic matter. I once had them overtake a shaded bed, but now have them under control. First, thatch the lawn and than add lime every year so the soil is less acid. Top dress the thatched lawn with sandy loam or pure sand and reseed with a shade tolerant grass seed if your lawn is shaded. Next keep the lawn thick and healthy by fertilizing at least twice a year in spring and fall. Aerate once a year and you will have a thick carpet of grass that will throttle the violets. Now all this is a lot of work. You could instead be very English ,and oh so country, and encourage the violets, buttercups and other blooming bits. Call it your wild flower meadow instead of a lawn and enjoy. Keep growing, Marianne Binetti