Horsetail, as a species, is more than 230 million years old and was once the dominant plant form on the planet. With that in mind, it is no surprise that it can be tough to get rid of. Horsetail spreads through ejected spores, and meters-deep regenerative rhizomes make a stand difficult to kill on the first try. There are, however, several physical removal methods that, when applied for three to four seasons, can control horsetail permanently. According to Purdue Extension Weed Science, horsetail's deep rhizomes and lack of absorptive leaves make chemical control ineffective.
Block out the sunlight. Because horsetail has no leaves, it needs ample sunlight to thrive. Erect a shade over the stand to completely block out the sun. Or, for a more attractive option, plant taller plants in the horsetail bed. Horsetail draws most of its nutrients from its rhizomes that grow much deeper than most plant roots. Consequently, horsetail presents little competition for other plants. For the best results, combine shading with cutting back.
Cut the horsetail tops back to ground level. Lopping shears can handle the mature stems of giant horsetail. Mowing is a great tool for repeatedly cutting back field horsetail growing in grass. For this method to be successful, you must recut the horsetail at least once every two weeks or as soon as you spot new growth. Repeated cutting in this fashion will eventually starve the underground rhizomes that feed horsetail and prevent its stalks from maturing enough to produce and eject spores.
Lay black plastic sheeting or landscape fabric over a recently removed bed of horsetail. Once horsetail is tilled or cut back to the ground, its new growth is not very strong. Install the plastic or fabric mulch over the stand according to the manufacturer's instructions. If left in place for three to four seasons, it will permanently get rid of the horsetail. In the meantime, desirable plants (except ground cover) can be planted in holes cut in the mulch's surface.
Withhold water. While not a control method in and of itself, inducing drought conditions can hasten the demise of a stand of horsetail. If the horsetail is growing where there is standing water, increase drainage in the area.