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Horsetail—the Weed that Shines your Pots and Pans!

Q. Mike: I've been an organic gardener since before you started editing ORGANIC GARDENING magazine. (McG here: that was back in 1990. ) But now I'm so bothered by a weed called horsetail that I'm thinking about giving up gardening! I have already mowed over my perennial garden because of this weed and sifted the roots out of the soil by hand. (Not easy for a lady approaching 70.) Now that my new plants are in, I go out daily and pull, pull, pull.

This weed is the worst I've ever dealt with. It spreads underground and via spores. I have read that I might be able to get rid of it if I solarize my soil for one summer, but I have a beautiful, productive asparagus patch as well as rhubarb and blueberries in the area.

I went to my extension service for advice; they have the same problem in one of their gardens! I've tried cardboard, newspaper and multiple types of deep mulch without any luck. And this weed seems to love weed block, sending out its invasive roots along the edges and poking through the fabric in less than a season.

I garden in cool USDA Zone 5 and have a nice sandy loam soil supplemented annually with home-made compost and purchased lobster compost. I use liquid fish fertilizer when needed and water deeply and infrequently. If you have any ideas about how to get rid of horsetail I would really love to hear them. Thank you,

---Sally in coastal Maine (less than 100 miles south of Canada)

A. Well, you can probably forget solarization no matter what, Sal. Utilizing the power of the sun is a great way to destroy weeds and diseases in soil, but as you note, you have to let the area bake under clear plastic for an entire summer to achieve success, and your far North region might not have enough of a summer to do the trick. Solarization works best in areas that receive a solid three months of hot and sunny weather.{See this previous Question of the Week for all the details on how to solarize your soil correctly.}

Now before we proceed to try and destroy it, let us first faintly praise this living fossil that is among the oldest plants in the world. (How old is it? So old that much of the coal we burn today was once horsetail.) The plant contains such large amounts of silica that it has served as a kind of natural sandpaper for millennia. Some gardeners deliberately grow it next to birdbaths so they can use the gritty plant to clean the saucer between fillings, and it's better than Brillo at scrubbing pots and pans. It's also attractive enough—kind of like a miniature pine tree —that it's been planted deliberately as an ornamental. (The people who did so probably felt pretty good about their decision the first few years, as it's very slow to establish. But when it does get going, you become a horsetail farmer.)

Like the equally invasive running bamboo, individual shoots come up from a massive underground root system, and so one of the ways to slowly get rid of it is to continually cut the new plants as they appear, weakening the root. It's vitally important to recognize and destroy the 'fertile' stems that appear in the Spring. Left undisturbed, the cone-like structures that appear at the top will disperse a mass of spores. (Oh and you can forget spraying it away; horsetail is highly resistant to herbicide attack.)

Now, if I were around 70 years old, I'd probably be comfortable sitting on an overturned milk crate and pruning those fertile stems as they appear. But for the season-long grind of constant culling, I'd suggest hiring a couple neighborhood kids for a few hours a day a few days a week. Teach them to soak the soil around the plants, then slide a trowel underneath each plant and lift it out slowly, being careful to keep as much of the underground rhizome attached to the plant as possible. If they can master the art of slowly lifting up large root systems, they should be able to clear good sized sections for you. When an area is clear, mulch it with something like six inches of wood chips for a year; it should be safe to replant the area after that.

Make the soil around those blueberries as acidic as you manage. Saturate the area with peat moss and add sulfur to bring the pH down under 5. The blueberries will love it, but I suspect the horsetail will suffer. In the asparagus bed, get the pH down to 6—asparagus likes an acid soil—and dust the bed with rock salt over the winter. This is typically done to prevent disease, but in this case we're hoping it harasses the horsetail.

And finally, horsetail thrives in wet soil. So try not to add any water to your garden; in your climate you shouldn't have to most years. And if any areas it infests hold water or drain poorly, consider core aeration with a machine that pulls plugs out of the soil. The better your soil drains, the less the horsetail will like it.

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