Horsetail weed is one of the oldest plants known on earth and may have been around for the dinosaurs’ salad bar. This plant is a great nuisance today, but traditionally was harvested and used as a rudimentary scouring tool. With little need for that today, gardeners and farmers find the weed difficult to eradicate. Gardeners have not found herbicides foolproof, however, and have come up with some other ways to kill horsetail weed. These include drowning it with vinegar and mulching with black plastic.
Horsetail can easily overcome a garden or field because it is a perennial and has two ways of reproducing. The weed reproduces both through its rhizomes sprouting underground and spores flying off the plant. The rhizomes branch out underground, often a yard deep. When you try to dig them out it is almost impossible to remove them without breaking them and each piece is capable of sprouting into a new plant. The horsetail spores are carried on the wind to the soil where they germinate and grow. Digging and hoeing horsetail weed may only help the weed to grow; the top part of its rhizome system alone will be affected and cutting into the rhizomes may just give them a better chance to sprout. Hand weeding may have a low impact; when Canadian agronomists weeded an area overgrown with horsetail more than a dozen times in one season, it robustly returned the following year.
What to Do
The good news is that horsetail can’t stand the shade. So blocking its access to the sun is one step. This can be accomplished, if the area is small enough to be covered, by heavily mulching horsetail weed with black plastic. Some gardeners knock the weed down and spray herbicide onto the broken stem before mulching. An organic 16-0-0 spray is sufficient. The herbicide should be high in nitrogen. If using an herbicide in a food-growing area, make certain it is safe to be used there.
A very eco-friendly method of getting rid of horsetail weed is to use vinegar. Some gardeners pour straight vinegar onto the soil in the horsetail patch. They report that if this is done on a dry day, weeds die and do not return. A horticultural vinegar is available that is more potent than household vinegar and may serve the purpose of destroying horsetail weed.
Plant competitors that will grow taller than the horsetail weed to shade any of the plant that returns.