Weed of the Month for May 2013 is Wild Violets

Wild Violet 

Biology: Collectively, turf managers refer to the Midwest species common blue violet (Viola sororia), wooly blue violet (Viola papilionacea), and confederate violet (Viola sororia f. priceana) all as wild violet. Additionally, yellow violet (Viola pubescens) is also found in Indiana. Wild violets are a persistent, perennial, and difficult-to-control broadleaf plant. It is regarded as a desirable perennial plant by some as well as a weed by others.

Common blue violet.

Wild violets in a shady lawn.

Wild violet leaf.

 

Identification: Violets can be identified by their heart shaped leaves which are pointed at their tip and have rounded teeth on their margins. Violets spread by short rhizomes and by seed. Short rhizomes about the size of your “pinky” finger are common to all Indiana wild violet species. Wild violets are typically found in shady areas with moist soil but they can also grow in sunny, droughty areas.

Wild violet rhizome on soil surface.

Wild violet plant showing rhizome after washing off soil.

Flower color varies by species. Common blue and wooly blue violets (both have a purple, blue, violet color. Confederate violet has white petals with an inner violet color. Yellow violet has a yellow color. 

Common blue violet. Wooly blue violets have the same flower color.

Confederate violet.

The confederate violet and common blue violet are often  found in the same area.

Yellow violet.

Following flowering and pollination, fruit capsules form. Seed is dispersed from the capsules by gravity after the capsules dry.  

Seed capsules.

Seed capsules after drying showing the dark-colored seeds.

Cultural control: Cultural practices such as proper mowing, fertilization, and irrigation can be manipulated to control some weed species but these practices have little impact on wild violet populations in lawns. Wild violet can be decreased by more frequent mowing but not by fertilization. It is unknown how irrigation, drainage, and soil compaction influence wild violet populations. As such, turf managers rely on herbicides to control wild violet.

If you wish to increase wild violets in your lawn, simply reduce your lawns nitrogen fertilization and maintain moderate to high levels of shade by withholding pruning of trees.

Biological control: Some organic herbicides are available. Among the postemergence organic herbicides, the most common are pelargonic acid (Scythe) and acetic acid (5 percent or greater solutions). Other products that contain medium-length fatty acids and clove oil (eugenol) show some promise; however, these organic postemergence herbicides are nonselective and can injure actively growing desirable plants in the lawn and landscape, so their use should be limited to directed spot treatments. The bottom line is that most organic postemergence herbicides have limited use in turf and are better suited to weed control in parking lots, fence rows, and other bare ground applications. Many new organic products contain the active ingredient iron HEDTA (FeHEDTA). Multiple applications of this product are required for control. FeHEDTA containing products injure turf less (can actually make turf darker green), but their efficacy for weed control is yet to be well documented.

Chemical control: Good chemical control of wild violet is typically obtained with triclopyr (Turflon Ester Ultra or Triclopyr 4). Many herbicides are available with triclopyr as the key ingredient (see Commonly Used Broadleaf Herbicide Combinations for Turfgrass, page 62). For best control with triclopyr use more than 0.5 lb ai/A. Turflon Ester Ultra and Triclopyr 4 at 1 pt/A will deliver 0.5 lb ai/A; and at 1 qt/A will deliver 1.0 lb ai/A. Chaser, Chaser 2 amine, Confront, 2-D, and Tailspin will also deliver ≥0.5 lb ai/A.

For more information on weed control, search this blog and archived turf tip postings and check out our Turfgrass Weed Control for Professionals Publication.

Aaron Patton, Turfgrass Extension Specialist