Horsetails (Equisetum spp.) are said to be almost indestructible. That was the heads-up I received at every turn when researching horsetails for “The Odd, the Tough, the Beautiful: Horsetails,” an article in the Fall 2021 issue of the UCCE Master Gardeners-Solano newsletter Seeds for Thought, https://solanomg.ucanr.edu/Seeds_for_Thought/?newsletteritem=90831. Gardening Web sites warn that horsetails should be planted in a pot or within deep soil barriers, preferably in a spot bordered by concrete. They are invasive and nearly impossible to get rid of once they establish where you don't want them.
I for one am delighted that horsetails are so resilient. My research was inspired by the horsetails in a city landscaping bed in my Suisun City neighborhood. Who knows how they got there—a windborne spore, or by spreading from the other side of the adjacent homeowner's fence? They were handsome. The sidewalk was bordered by a vertical wall of green that would never interfere with pedestrians. Moreover, city landscaping beds where I live grow mostly weeds, but that horsetail patch had none.
A few months ago, city landscapers tasked with weeding mowed and herbicided those horsetails. If only they understood that they were shooting themselves in the foot by killing desirable, zero-maintenance, weed-suppressing plants! The horsetails appeared to be stone dead. It was very discouraging.
Imagine my joy when they started roaring back! Lots of new green horsetail stems have already popped up among the yellow stubble and dead stalks left by the landscaping crew. It seems miraculous, and bears out horsetails' reputation for toughness. Toughness has its limits, though, and I worry about repeated attempts to wipe them out. So I chalked a sign on the fence: “LANDSCAPERS PLEASE DO NOT MOW OR KILL THESE PLANTS.” I hope it works.