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Ridding The Garden of Horsetail (Equisetum)
by Fred Davis, MG, Hill Gardens of Maine
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Welcome through Fred's Garden Gate! Have you noticed the rampant spread of horsetail (Equisetum) into gardens and public landscapes during the past few years? It's the subject of an ever-increasing volume of queries directed toward professional gardeners all across the country. Where does this stuff come from and how did it get into those landscapes? Is it controllable? How? And the most telling question of all: Why doesn't this [insert popular herbicide name here] kill it?

Listen to this recent urgent plea from a desperate gardener:

"Help! I am dreading the return of horsetail this year! I have a beautiful mulched slope in my front yard that is landscaped with evergreens, rhododendrons, azaleas, bulbs and a couple of pretty flowering crab trees. This area slopes to a culvert which is a wetland and has swamp irises in it - really a potentially fun project. BUT. . .coming up through the mulch is horsetail! We just moved into the house last year, and tried - via gallons of RoundUp - to get rid of this invasive wild vine, but it still took over and is not a bit attractive. We would appreciate any and all suggestions that you can give us. Sandy."

I hear similar scenarios from garden visitors and emailers several times each season. Sources of this garden invader usually alternate between "nearby wetlands" and "We had a load of mulch brought in last year and. . .." It's often seen in professionally maintained landscapes near mid- to up-scale businesses and in shopping center parking lot plantings. Occasionally, a new outbreak appears near the base of recently installed trees and shrubs, or next to a plant dug from a roadside or moist wilderness meadow. While the most common home garden source is a nearby wetland, an inescapable conclusion is that a great many new infestations emerge from delivered loads of landscape bark mulch and, sadly, containerized or "balled-and-burlapped" plants. Nursery stock and shredded bark have long been a source of highly-invasive weeds and aggressive grasses. All of which points up the need to choose your mulch or plant sources carefully. Buy only from reliable and if possible, local sources. Reject any containerized plant that is either choked with weeds or is displayed on weedy ground—specially if those weeds have seed heads showing.

Horsetail (Equisetum) is easily among the most tenacious and pernicious "weeds" of all...having endured millions of years evolving beyond most of the trifling defenses that inventive and desperate modern gardeners have thrown in its inexorable path. Giving the impression of being diminutive, long-needled, single-stemmed pine seedlings ranging in height from a few inches to as much as one-and-a-half feet, horsetail's thin black roots typically travel underground several feet during a single season before emerging as a new plant. Pulling it up at that point serves only to force the undamaged underground structure to strike out in new (or several new) directions, exacerbating an already nearly unmanageable situation. But there is some good news to go along with all the bad.

First, the good: Virtually every creature (us included) can--and often does--use horsetail for food. Tender growing tips, for example, stir-fried in extra-virgin olive oil with other veggies, greens, and diced chicken breast, add a pleasant taste and texture. There may even be some nutritive value of which I'm not aware.

Now, I fear, the bad news: There are four approaches to dealing with horsetail...not all of them, you might agree, entirely acceptable.

1. As Sandy (in the email question, above) tried, you can spray repeatedly with RoundUp during early, active growth. Every time it gets three or four inches tall, hit it again! Don't waste time spraying tough, old granddaddies...whack them down and wait until re-growth has reached the optimum height for treatment. (See note, below.)

2. Horsetail cannot abide cultivation--total, deep, disrupting, chopping, ripping, tearing, removal and destruction--which, considering Sandy had already tried RoundUp, may be her most viable option. Oddly enough, I have a similar situation in part of our gardens. Highly-improved soil in a daylily display bed next to a low, wet spot. Horsetail discovered the enriched soil and literally exploded into it with a vengeance! The only recourse: rescue and totally bareroot the daylilies to remove all traces of the pest, then go after that healthy crop of horsetail with every weapon in the arsenal: shovel, wheelbarrow, cultivator, and spray—plus considerable time and at least two pair of really soiled jeans. It'll take the entire season of growth-kill, growth-kill. Sadly, of course, the adjoining wet spot is still there and I'm sure the horsetail will be back. A perennial battle.

An added thought: unless you elect option #3, never allow any tenant or bordering horsetail to mature its seed heads. Snap off and destroy any that you see. While they don't really need seeds to spread (horsetail does that very well underground), they'll be much easier to evict from landscaped gardens if the soil isn't infiltrated by quantities of both seeds and root-runners. Seeds, cultivated below the soil surface, can remain dormant—and fully viable—for years waiting to be re-cultivated back to the surface.

3. Rescue your desirable plants, meticulously clean them up, plant them somewhere else, cut your losses, and run. Abandon. Perhaps not an acceptable option.

4. One final option remains: horsetail will have little effect on established shrubs and trees beyond absorbing their share of water and nutrition, and is actually not all that unattractive in a mass-planting...sort of like a rich, green carpet. You'd want to rescue the bulbs and other small specimens...but a population of Siberian Irises of different colors, heights and bloom-times, for example, in a sea of green, occasionally-manicured horsetail, might make an attractive display. Just a thought. On second thought, naw!

Whatever you decide, neither you nor Sandy will probably ever completely rid yourselves of this wretched wetland pest...and controlling it will be a lifelong battle. My inclination is to somehow learn to live with it—and suffer far less wear and tear on the back, jeans, heart, and soul. Besides, even though manufacturers claim that certain herbicides are completely safe, I continue to harbor reservations about any yet-unrevealed possible long-term consequences of repeated use on 'Ol Mother Earth and around the homes of Her inhabitants.

Note: Considering Sandy's use of the word "gallons," I suspect she applied the seemingly-less-expensive, pre-mixed, "hobby-gardener" version of RoundUp with the convenient little built-in hose and trigger-sprayer instead of a conventional cap. In my opinion, that would be a perfectly acceptable choice to knock down a few dandelions, chickweed, or plantain, but when it comes to these rugged ancient dwellers of the primeval swamp and prehistoric wetlands that have invested eons in developing toughness—the pre-mixed formula just isn't strong enough! Go for the concentrate. It may appear to be more expensive at first glance but, when you figure the gallons and gallons you'll get from concentrate, and compare that with the price of all those gallons and gallons of as-yet-ineffective pre-mixed solution, there's a significant savings in both money and end result. For the 25% concentrate, apply at the rate of 1-1/2 to 2 ounces per gallon of water, and use a coarse spray on a very calm day, early in the morning. I'd recommend you work together with an assistant who will carry a large piece of cardboard or poly sheeting to protect valued plants from drift and misadventure. Be very careful about where you walk after you've sprayed—you'll get some of the material on the bottoms of your shoes that may result in a trail of thoroughly-dead footprints across an adjoining lawn. Wash your hands and clothes immediately after spraying to prevent accidental transfer of residues to houseplants, and to avoid any unforeseen potential complications. AND, as always, read the entire label before mixing.

 
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