I have several raised vegetable garden beds that have been overtaken by Purple Deadnettle. What is the best way to handle this problem? Removing Purple Deadnettle so it won’t come back? Colleen Harns Eaton Rapids, MI
Eaton County Michigan
Colleen, purple deadnettle is a winter annual weed species, so it germinates in the fall, overwinters and then flowers and produces seed early in the spring (now). After seed is produced the plants die back and you are unlikely to see any during the summer. For the most part they do not compete with too many of our annual vegetables because their lifecycles don't usually overlap when vegetables are most vulnerable, but they can vector other pests in some instances and compete with very early planted veggies.
There are a couple things you can do to combat this weed. The first would be removing as much purple deadnettle material as you can now to prevent more seed from entering your raised beds. Once your garden is planted applying mulch of some kind can reduce overall weed emergence by preventing light from reaching the soil surface and by creating a physical barrier. To prevent purple deadnettle emergence you would want to make sure that mulch was present in late-August throughout the fall. Here is an MSUE article with some information about mulch types https://www.canr.msu.edu/news/mulch_for_the_vegetable_garden
There is also a herbicide option if you are not going to be planting any vegetables from seed in late-summer through fall. The active ingredient is called trifluralin and it prevents weed from successfully emerging from seed. There is a product labeled for use in vegetable gardens called Preen Garden Weed Preventer that can be found at many of the big box hardware stores. Be sure to read and follow all labeled instructions with any pesticide application to ensure maximum effectiveness and personal and environmental safety.
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