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Mints - friend or foe?

Mint plant
Rhizomatous roots and creeping stems

Mints have square stems.
 Plants in the Mint family have a well-know reputation for being aggressive. Some, like creeping Charlie Glechoma hederacea) are common pests for many homeowners and gardeners. Wild mint (Mentha arvensis) is a Minnesota wildflower.

Mints can most easily be identified by their square stem and fragrant leaves when crushed. Mints are aggressive and have rhizomatous root systems and creeping above-ground stems, making them difficult to eradicate. Mints grow well in sun and shade, and are adaptable to various soils. Many mints are grown for culinary use, and mints - including creeping Charlie - are good sources of nectar for pollinators. Still, some people want to eliminate large areas of wild mint (and creeping Charlie) from their landscape. There are essentially three options: (1) treating the area with a broadleaf herbicide with glyphosate + triclopyr. (2) Solarization using clear plastic sheeting. (3) Dig out the plants, removing as much of the plant root as possible.

(1) Spraying a broadleaf herbicide would be the fastest option. However, the broadleaf herbicides noted above are non-selective and will most likely kill every plant. So it is important to treat the area on a calm day (no wind) and to protect desirable plants with mechanical barriers such as cardboard pieces / boxes, leaf bags, tarps, etc. These should be left in place till the sprayed foliage is dry. Always follow the instructions for proper chemical use, storage and disposal on the product label.

(2) Option two is solarization. Plants are cut back and sheets of clear plastic (not black) are laid down tightly over the plants. Solar energy will heat up and kill the plants and seeds. The plastic should stay in place until plants have died back completely. According to the University of California IPM website, this may take 4-6 weeks depending on the intensity of the sun's energy, number of sunny days, and the plants' resiliency.
(3) Option three- and most labor intensive - is digging out the mint. Because mint can vegetatively propagate - grow from a small piece of root or stem - it is important to dig out as much of the root as possible and resist pulling the plants out thus breaking the roots. Digging out the plants could be done in conjunction with Option one or two as well.

After eradicating the mint, it is important to follow up regular weeding and treatment as necessary. If re-establishing lawn, choose grass seed appropriate for the site and re-seed as per Lawn Renovation. For landscape beds, mulch the area with 2-3" of wood mulch and / or replant with preferable plants. See Extension publication Mulching the Home Landscape. Typically, landscape fabric is not recommended nor is it necessary; however, because the goal is to prevent a perennial from re-sprouting, fabric is an option under the wood mulch.

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