I would like to tarp lily of the valley and periwinkle. Can I do this starting in August and remove the tarp in April?
Hello, thank you for contacting the Toronto Master Gardeners for help with your invasive plants.
Soil solarization (or Tarping over) is a wonderful way to rid your garden of weeds. However, I am sad to say it will not alone solve your invasive plant problem. The two invaders that you mention are two of the most difficult to eradicate. I have been battling these two foes for many years and the solution does entail a great deal of work. Lilly of the Valley spreads very quickly and effectively through its thick rhizomes, while Vinca’s vigorous roots can root simply with contact with the soil. Because of these specialized root systems any piece of root or rhizomes left in the soil can grow into a new plant. Manual removal is really the only way to go with these guys. You must dig down to beneath the level of the roots, removing the soil or manually sifting the soil to eliminate any part of the plant. Yes, it is a very big job! Having said all of that, Soil Solarization may aid in this endeavor. By heating and burning up the plants above ground you will weaken the root structure, thus making the job of digging out the roots easier. Plus digging out these plants will be a whole lot easier in April when the soil is moist– after some heavy spring rains. Once you have accomplished both tasks and have replanted your garden, make sure you mulch heavily and keep an eagle eye out for any remaining stragglers. I am attaching a link for soil solarization that you may find useful. I wish you luck with your mission.