The wild violet (Violet pratincola) is a spring-flowering, shade-loving perennial that proves that one person's treasure is another's trash: for every gardener who loves that dense mat of heart-shaped leaves and purple or white flowers, there is another intent on eradicating wild violet from her lawn. Wild violet control can be quite difficult, as the plants are drought- and cold-tolerant, and spread by seed as well as by rhizomes -- horizontal root networks that form a dense, growing colony of interconnected plants. Use multiple applications of an appropriate herbicide to control wild violets in your lawn.
Select an herbicide appropriate for your lawn type, and which has been approved and labeled for broadleaf weed control in home lawns. Read the labels carefully to ensure you have the correct herbicide product.
Mix the herbicide with water in a hand-pump sprayer, in proportions according to the manufacturer's directions. Do this in the early autumn. Add spreader-sticker compound to the herbicide and water mix according manufacturer's directions, or add 1 tbsp. of light vegetable oil per gallon of mix to help the herbicide stick to violet's waxy leaves.
Spray the wild violets thoroughly. Wait three weeks, and spray again following the same process.
Wait three weeks after second spraying. Use a spading fork to puncture and loosen the dirt in the area where the violets were growing. Pull up the largest root masses and discard (do not compost).
Spread a 1/2-inch layer of compost over the area loosened with the spading fork. Broadcast shade-tolerant grass seed lightly over the area, at a rate of about 1 cup of seed for every square yard. Water lightly, then cover loosely with a very light layer of straw mulch. Water one or two more times before freezing winter temperatures set in.
Monitor grass growth in the spring. After the newly seeded area of lawn has been mowed three times, spray again with herbicide mixture. Repeat the following autumn if violets return.