Wild violets are native to North America and a member of the violet family or Violaceae. Several perennial species of violets are found in New England and free hybridization can make it difficult to distinguish among them. Common blue violet (Viola papilionacea) is often considered a weed in landscape and turf areas. Heart-shaped and regularly-lobed leaves are attached to crowns with long petioles. The foliage is frost hardy and remains mostly evergreen, but will decay when covered with snow and ice for long periods. Plants form a dense, fibrous root system. Five-petaled purple or blue flowers (occasionally light purple, grey or white) with white or yellow centers arise from crowns on leafless stalks from April to June. These flowers are approximately the same height as the foliage and usually infertile. Violets also produce fertile cleistogamous flowers. These less conspicuous, self-pollinating flowers are produced closer to the ground, never open and bury themselves under the soil surface. Small fruit capsules split in three maturities. Reproduction is also from short, branching rhizomes. Violets grow best in moist, fertile, cool and shady areas, but can establish and persist in sunny and/or drought prone locations.
Wild violets are persistent perennial weeds and one of the most difficult in the world to control. Violets can be eliminated from turf or landscape areas with repeated hand-pulling or digging which attempts to remove all vegetative portions of the plant. This can be very tedious and diligence is required. Direct applications of glyphosate (Roundup™, Touchdown™) can be used in ornamental beds, nurseries and non-turf areas. Control of wild violets in turf areas will require the use of a postemergence broadleaf benzoic acid (dicamba) herbicides may require several applications over an extended period of time and most often will result in only fair control. The best control is provided by triclopyr, either alone or in two- and three-way combinations with other broadleaf herbicides. Products include, but are not limited to, Confront™, Momentum™, Chaser™, Chaser 2 Amine™, Battleship™, Turflon Ester™. Applications of broadleaf herbicides should be maden between late April and mid-June or early September to mid-October. Frequently, two or more applications are needed with fall application generally being more effective.
Keep in mind that this weed is extremely difficult to manage. A reasonable goal for the first year would be to prevent the spread of the existing population. If control attempts fail, perhaps one should try to appreciate the attractive flowers of this tough to manage weed.