Answer: Horsetail spreads by deep, deep roots and can pop up almost anywhere in the garden from a single plant. It likes moist soil so if you can keep the soil on the dry side or improve the drainage, that will help discourage the weedy growth. There are no chemicals effective on horsetail. While they may kill off the tops of the plant, the underground roots will simply send up new shoots. I had a hillside filled with horsetail and found the best control was to simply mow it down on a regular basis. Keeping the tops cut or mowed down eventually starved out the roots of the plants. You can do the same thing but the key is to cut down the sprouts as soon as they emerge. This way the roots are expending energy to send up the shoots but cannot recover that energy without photosynthesis. So, just keep chopping the tops of the weeds down and you'll eventually starve out the roots. Good luck with your project.
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