What you have is Viola sororia, common blue violet. It is native to eastern North America. It is known by many names, meadow violet, purple violet, wooly blue violet, hooded violet, dog violet, and wood violet.
As you know, the plant spreads very well and it does spread to lawns, especially along hedges and buildings. It prefers shade and moist locations. It can become very aggressive in lawns. If you can live with it in your grass, it is green and it does have benefits for some wildlife.
Common blue violet is the host plant of the caterpillars of many Fritillary butterflies who feed on the foliage. Wild turkeys feed on the roots and seeds. Mourning Doves and Juncos eat the seeds and deer and rabbits feed on the foliage.
Violets are not easy to get rid of because they spread via rhizomes – a creeping horizontal root that produces new shoots. These little guys also self-pollinate and produce seeds that insures the next generation of plants.
Hand weeding, although labour intensive is the least harmful way to rid your yard of these plants. Hand weed in spring and summer when the plants are growing the fastest. Dampen the soil and use a hoe so you can pull out the entire root system. If you just remove the leaves and flowers, the rhizomes will continue to re-sprout. A day or two after hand weeding, add a layer of mulch to suffocate any small bits of root left behind.
If they have taken over a large area of lawn, you could try laying out layers of cardboard or newspaper covered with mulch to smother the plants. This however is not a quick solution. It may take months for the plants to decompose but it will result eventually in a weed-free area.
To keep the violets in check you need to have well maintained lawns and beds.
Wild violets like shade so prune back trees and overgrown shrubs along the lawn edge to allow more sunlight in to allow the grass to grow.
Wild violets love moist soil so improve the drainage of your lawn, aerate your soil and mix in a coarse organic material like sand.
None of the solutions I have suggested are quick and easy. It may be something that you need to work at over a few seasons.
authored by Carol Anderson