Wild violets (Viola papilionacea) are a native North America wild flower and are often considered a weed in landscaping. The leaves of the wild violet are heart-shaped and connect to small flowers. The plant is frequently evergreen, although long periods of being covered by snow or ice may brown the leaves. The flowers can be white, purple, or blue and generally bloom between March and June. Wild violets thrive in cool, shady, moist areas, but they can also grow in sunny and dry areas of the garden. Because wild violets develop thick, dense roots, and because their leaves are waxy and resistant to herbicides, they are difficult to kill. In fact, when herbicide is applied and all other weeds (including persistent dandelions) die, wild violets often persist.
Pull all the plants you can by hand, digging up the roots with a spade. The Weed Hound Weed Puller also works well on wild violets. For best results, begin digging about a foot away from the centre of the violet, which makes it easier to lift the entire plant -- roots and all -- from the soil. Take great care to dig up all the visible roots, including those that break away from the violet when you dig it up.
Spray chemical weed killer on persistent wild violets that aren't in the lawn. Use a spray with glyphosate, like Roundup or Touchdown.
Apply a postemergence broadleaved herbicide to wild violets in the lawn. For best results, choose a product with triclopyr, like Ortho Brush-B-Gon, Ortho Weed-B-Gon Chickweed, Clover and Oxalis Killer, Enforcer Brush Killer, Confront, Momentum, Amine, or Turflon Ester. Typically, you must visit a professional landscaping store for these herbicides. For best results, use the product between early September to mid-October or late April and mid-June. More than one application may be necessary.
Contain wild violets you want to keep. Do not allow wild violets in your ornamental garden without potting them first. If you wish to hide the pots, dig a hole in the ground. Place the pot and plant in it. Cover it with soil. Even when this precaution is taken, wild violet roots may escape and invade other areas of the yard, so watch the plants closely and pull any invading new plants promptly.
Alter the chemistry of your soil. Wild violets love acidic soil; an alternative way to try to decrease their population is to add lime to your soil after testing its current pH level. However, violets may continue to thrive even after the soil chemistry is altered.