Hi LAinSEA!
Those horsetails sound very nasty!! Here's some info I found on getting rid of them, I sure hope it helps! Let us know if you need more.
Horsetails in my Garden
Q. I have tried everything I can think of to get rid of horsetails, from digging them out down to the nub of the root, to herbicides, to just chopping them off. We did a major project on what was a swamp and now the horsetails threaten to take it all back. Someone told me to use diesel fuel, but I don't want to do that. Is there anything that is a little more environmentally friendly but still effective?
A. "By all means don't use diesel fuel!"
setum is the botanical name of the weed that's causing all the frustration for you. It sounds like the area is still moist enough to promote the growth of this wetland plant. Horsetails are a "primitive" plant with a vascular system such that herbicides will only kill the top of the plant, but not travel down to the roots. As you've discovered, the roots can grow both down and sideways for 10 to 12 feet. It's a formidable opponent of more desirable plants in the garden. If you're persistent you can keep the tops of the plants cut down as they sprout, and eventually you'll starve the roots out. Perhaps if you improve the drainage in the area, it will lose its competitive edge against your garden plants.
In lawns, simply mowing the grass at regular intervals is sometimes enough to wipe the horsetails out -- but it can take two or three years. Some gardeners have had success with the flame weeders -- torches designed to burn weeds out of tight place, such as between concrete walkways and driveways. If you use a flamer, you don't need to cremate the weed, just pass the flame over the plant's tissues long enough to heat the fluids, which in turn rupture the leaves and stems. If you're persistent with your eradication treatment, you'll prevail."
