Horsetail weeds are a children's favorite, offering frothy swords and a distinctive squeak as their segments are pulled apart. Adult gardeners, however, have far less enthusiasm for this remnant of the Sphenophyta family, which has persisted for approximately 30 million years. In the absence of dinosaurs to eat it, gardeners dig, mow, smother, pull and occasionally curse this determined invasive. Understanding the qualities that have enabled this ancient plant to survive are key to removing it from locations.
Look at the size of the horsetail infestation, as this is what will govern your efforts. Recognize and address the two survival mechanisms that have preserved the horsetail throughout the centuries. Horsetails spread by spore-laden buds in early spring, then continue to send out long rhizomes to add additional plants. Removal strategies need to address both methods of propagation.
Attack buds in the spring with cutting tools or a mower before spores are shed. The goal of repeated cutting, say experts, is exhaustion as well as containment. Cutting buds repeatedly will weaken the underlying plant.
Stop the growth of horsetails by obstructing their access to light. Several layers of impermeable black plastic mulch fabric and several seasons of use may be required to block horsetail growth. Watch the edges of the covered area for new sprouts from rhizomes; horsetails have lasted so long because of their abilities to persist under duress.
Spray the weeds with new vinegar-based sprays, which are designed to penetrate the plants' tough outer sheaths, which make horsetails resistant to most herbicides. Sprays, while containing natural ingredients, are strong and work best in isolated infested areas, where they are unlikely to affect surrounding plants you want to keep. Sprays will highly acidify soil, and it will need nutritional rebalancing once horsetails are eradicated.
Work and be as persistent as this ancient plant. Horsetail removal is seldom a single-day or single-season event, even with herbicidal help. Take a moment to admire the resources that have enabled the plant to survive from before the times of humans on the earth, then go back to mowing, digging and removal.