Violets in my grass

(Question)

The links to how to get rid of violets in my grass show no answers are available. Please let me know how to get rid of them. They have taken over a very large part of my lawn.

(Answer)

Thank you for contacting the Toronto Master Gardeners with your question on getting rid of violets in your lawn.

Violets spread aggressively through your garden because they reproduce by both seed and underground rhizomes. The non-native violets ( Viola odorata) is now on the potential invasive species list. Our native violet is a larva host plant for the Fritillary butterflies. Wildflowers Ontario gives tips and photos on how to identify our native Violets.

If your patch of violets is not too large, you can try digging it out making sure to remove all of the roots and rhizomes.. Even if a small piece of the rhizome is left this will sprout a new plant. To prevent seeds from spreading make sure to cut off the flower heads before they set seed. 

Of course, the best method of keeping all weeds out of your yard  is to have a thick, vigorous, and healthy lawn. Improving the soil quality with the yearly addition of organic compost and overseeding will aid in improving the quality of the soil and lawn. Landscape Ontario has a month by month guide on How to Maintain a Healthy Lawn.

If your infestation is very large you can try covering the area with black (occulation) or clear plastic (solarization). It should be noted that this will also kill whatever grass is there.

Covering the ground with thick black plastic is an effective way to kill weeds. At first the weeds will begin to grow rapidly due to the heat under the black plastic; however, over time, they will die from lack of food. Essentially, the weeds will starve since they cannot produce food through photosynthesis and eventually will exhaust their food supply. This method takes time and will only work as long as no light reaches the plant.

Another effective non-chemical technique to eradicate weeds is through solarization. According to the University of California Integrated Pest Management article titled Soil Solarization for Gardens & Landscapes 

The method involves heating the soil by covering it with clear plastic for four to six weeks during a hot period of the year and when the soil will receive the most direct sunlight. Plastic tarps allow the sun’s radiant energy to be trapped in soil, heating the top 12 to 18 inches to temperatures lethal to a wide range of soilborne pests; including weeds, plant pathogens, nematodes, and insects. When properly done, the top layers of soil will heat up to as high as 140°F, depending on the geographic location. Soil moisture is important in this process, as wet soil conducts heat better than dry soil. Moisture also makes soil pests, weakened by the heat, more vulnerable to attack by beneficial soil microorganisms during and after treatment.”

It should be noted that soil solarization kills all organisms in the soil even the beneficial ones. However, according to Texas A&M Horticulture article on Soil Solarizationbecause solarization kills all organisms—even the beneficial ones—farmers and gardeners should replace the beneficial organisms by adding compost to the soil after it has been solarized.”

Good Luck!

May 7, 2021