Horsetail is a perennial weed that spreads through deep rhizomes. According to Ohio State University, the rhizomes will spread 330 feet horizontally and 20 feet deep. This makes the weed difficult to remove. Mechanical cultivation will spread the weed as each broken rhizome will produce a new plant. Removal of the food source generally is the best cultural control. Herbicidal control is an annual process because of the deep root systems.
Remove the tops of the horsetail plant, within two weeks of the green plant's emergence from the soil, by cutting them off at ground level with the shovel. The lack of the green shoots will restrict food intake to the rhizome root structure.
Practice the green shoot removal for period of three to four years for effective cultural control.
Layer the area with a plastic sheet as mulch to heat and suffocate the weed. Cover the plastic mulch sheet with a wood bark material to hold it in place.
Apply the herbicide dichlobenil to the horsetail plant. According to Washington State University, the most effective time of year for this herbicidal application is in mid-winter. Many herbicides have proven ineffective to the horsetail plant. Consult your local agricultural extension service for other herbicide control in your area and climate.
Follow all label direction in the application of the herbicide. Repeated chemical treatments will be necessary to eradicate this noxious plant.