Horsetail: The Good, the Bad and the Ugly
We’ve had a number of questions this season about a weed known as horsetail, Equisetum arvense L. The plant, which grows just about everywhere in the U.S. except Florida and other parts of the deep South, is one of the most annoying in the garden if you’re trying to keep it clean. Others, however, love horsetail for its various uses in the kitchen or medicine cabinet.
I’ve never known it to be a huge problem on lawns that are mown regularly, but the plant can be nasty in perennial gardens and orchards due to a deep root system that only flourishes more when you break off the upper stems.
Here’s what you need to know before you decide how to deal with the plant:
THE GOOD SIDE: A “bio-accumulator” like dandelion, horsetail takes up all sorts of nutrients from the soil including copper, lead, zinc, cadmium and even gold. Holistic gardeners use extracts of field horsetail make fungicides for blackspot on roses and rust in mint. It has herbal uses, too, and many cultures see the shoots of horsetail as a valuable food source. I’ve never tried it myself and I don’t recall my grandmother gathering the stuff, but I do recall the painter Neil Welliver — a great organic gardener by the way — telling me that his family used to eat the stuff.
THE BAD SIDE: Horsetail is a true nuisance in fields since it’s toxic to sheep, cattle and horses. Hay with too much horsetail is considered a waste material.
THE UGLY SIDE: As a “weed” in the garden, it can be very difficult to eradicate without true diligence. The roots can reportedly grow up to 200 feet long, although I’ve never witnessed them more than a mere 10 feet or so. However long it grows, those roots pose the problem, since a new conical horsetail can easily emerge from any point on a broken piece of root.
ERADICATION — Don’t try just pulling or rototilling the plant out because it will most certainly grow back if nothing else is done. Black plastic sheeting or rubber pond liner or roofing underlayment works well. Depending on the time of year, you’ll need to leave the plastic or rubber in place for four to 12 weeks; the warmer it is outside the faster this control will work.
Like virtually all weeds, the presence of horsetail is an indicator of various soil conditions such as excess moisture, low pH, and poor drainage. Regular mowing and leaving the grass plants tall will help eradicate the plant in a lawn area.