I have been trying for years to get rid of the "horsetail" in my garden to no avail...any suggestions?
Van Buren County Michigan weed issues
Yes, horsetail (Equisetum arvense) is one of the most challenging weeds to control in the landscape. Here is a bit about the plant, along with control recommendations, from our weed specialist, Dr. Erin Hill:
Field horsetail (Equisetum arvense), also known as scouring rush, is a perennial, spore-producing plant with a prolific rhizome system that can grow to a depth of 6-10 feet or more. Field horsetail has two stem forms. The reproductive form appears as erect, unbranched, white to brown fruiting stalks (stems) which emerge in early spring and bear terminal spore-releasing cones. Vegetative stems are green, branch in whorls and give the plant a bottle-brush appearance. These stems emerge later in the spring and should not exceed 2 feet in height. Field horsetail is a common weed of landscapes, orchards and nursery crops. It is often found in areas of poor soil drainage or where the water table is high. It can also grow particularly well in sandy, gravely soils or neutral or slightly basic soils. Once established, field horsetail can tolerate many habitats.
Control. Anything that can improve surface and subsurface drainage may help reduce the competitive nature and incidence of field horsetail. Mechanical control options include hand pulling shoots and what rhizomes/roots you can dig up. Plants can spread if rhizomes are chopped and not removed, therefore try to get as much as possible and dispose of in the trash, not in compost. By mechanically removing the parts you can get to you may be able to starve the extensive root system over time, but it will require constant vigilance over several years. If soil removal is an option, soil would need to be removed to 6 feet or more. If that is not possible, placing a geotextile fabric in a shallowly excavated area before back filling with new soil would prevent rhizomes from entering the bed. Fabric must be placed on the bottom as well as the sides of the hole.
Chemically treating the plant with herbicides is problematic because of the biology of the plant. The high silica content of the stems limits herbicide absorption and extensive root system often results in regrowth. Field horsetail is tolerant to most herbicides used in the landscape. Homeowners have had some success with repeated applications of glyphosate (the active ingredient found in Roundup Weed and Grass Killer, and other generics). Glyphosate will injure desirable plants with which it contacts as a spray or drifted spray. Remember, always read and follow labeled directions and be sure that the chosen product does not contain additional active ingredients as this could impact the ability to replant in the area.
If there is visible water located near the site at the time of application or it is along the Lake Michigan shoreline (or any of the Great Lakes or Lake St. Claire) a permit is required prior to making a herbicide application; contact the MI Department of Environmental Quality (DEQ) Aquatic Nuisance Control Program Staff at (517) 284-5593 for more information. Also, a list of approved aquatic herbicides needs to be consulted on the MI DEQ website (https://www.michigan.gov/documents/deq/wrd-anc-approvedherbicides_445623_7.pdf). Glyphosate products are available on that list.
Hope this helps. Good luck.