Horsetail (Equisetum hyemale)—also called rough horsetail or scouring rush—is a non-flowering evergreen perennial. It has vertical green stems with horizontal bands similar to bamboo, but they're skinnier and taller like ornamental grass. Similar to ferns, horsetail reproduces through spores rather than seeds, as well as underground rhizomes.
Horsetail is such an aggressive spreader it would likely be considered invasive if it weren't native to North America (as well as Europe and Asia). This is an important consideration when planting horsetail anywhere outside of a pot. To prevent it from taking over your garden or other planted ground, it's advisable to use soil barriers or another form of containment.
Horsetail is usually planted in early spring, though it will survive planting at almost any time. This is an extremely fast-growing plant that achieves full height within a matter of weeks. Under ideal circumstances, a clump of horsetail can spread more than 100 feet within a year. Horsetail is toxic to grazing animals.
|Common Name||Horsetail, rough horsetail, scouring rush|
|Botanical Name||Equisetum hyemale|
|Plant Type||Evergreen perennial|
|Mature Size||2–4 ft. tall; 1–6 ft. wide|
|Sun Exposure||Full sun, partial shade|
|Soil Type||Moist but well-drained|
|Soil pH||Neutral to acidic|
|Hardiness Zones||4–9, USA|
|Native Area||North America, Europe|
|Toxicity||Toxic to grazing animals|
Far from a fussy plant, horsetail is often more challenging to contain rather than grow—the plant has a strong tendency to spread and form a monoculture. On the other hand, if you'd like the plants to fill an area that is unfavorable to most other species, the spreading ability of horsetail is desirable.
To contain horsetail planted in the ground, install plastic barriers in the soil, the same method you can use to contain invasive bamboo. Another option is to plant the horsetail in a deep pot buried in the ground. However, because horsetail also spreads through spores, containment will still be challenging.
Horsetail grows in wet conditions and can even grow in standing water. For this reason, it is commonly used to decorate water gardens or swampy areas where few other plants can survive. It's also commonly grown as an accent along borders or in large patio pots, similar to how ornamental grasses are used. As befits a plant with a reputation for invasiveness, horsetail has no serious threats from pests and diseases.
Thanks to aggressively spreading underground rhizomes, horsetail is considered highly invasive and therefore it is important to contain the plant properly if you choose to grow it. It can become invasive anywhere, though populations are particularly high in the Pacific Northwest.
Horsetail is extremely adaptable to various light levels, growing in every condition, from full sun to partial shade. That being said, it prefers filtered shade, such as that found on the forest floor beneath tall trees.
Horsetail thrives best in poor, sandy, gravely soil that is frequently wet. In fact, the more fertile the soil, the slower the plant grows. When growing horsetail in a container, consider adding gravel or sand to the potting mix to give it the texture the plant enjoys.
When it comes to soil moisture, horsetail prefers soil that is at least moderately wet. It can even grow in standing water up to a depth of about 4 inches. Because of this, it's well-suited for rain gardens and other areas that may periodically flood.
Temperature and Humidity
Horsetail plants prefer high humidity for several hours a day and thrive in a variety of temperatures. Winter care is not a concern, as the plant is hardy to USDA zones 3 to 11, though the bright green of the stems may fade during especially cold winters.
In general, horsetail plants do not like particularly rich or fertile soil, so fertilizing is not necessary.
Types of Horsetail
Although there are no direct cultivars of Equisetum hyemalis, there are several related species also known as horsetail. Some of the most popular options include:
- Equisetum arvense: Commonly known as field horsetail or corn horsetail, this plant is generally categorized as a weed because it is every bit as aggressive as Equisetum hyemale but lacks its redeeming aesthetic qualities. Field horsetail can grow up to 20 inches tall, but it's often stunted by the dryness of the earth in which it grows so that it reaches only about 8 inches tall or less. Many landscapes become overrun with field horsetail; it will spread even under the driest conditions.
- Giant horsetail (E. giganteum): A Central- and South-American native, this plant is only hardy to zone eight. It can be grown in full sun or partial shade and can become 10 feet tall or more.
- Variegated horsetail (E. variegatum): A shorter, hardier plant that is native mainly to the wetlands of the northern U.S. and Canada. It's termed "variegated" because its black-and-white sheaths (on otherwise green stems) show up better than those on E. hyemalis.
While horsetail isn't pruned in the traditional sense, the main challenge is keeping this plant under control or eradicating it where it is not wanted. Horsetail can extend its roots under sidewalks, garden walls, and driveways, so elimination requires carefully digging up and removing all root pieces.
It may also be possible to eradicate horsetail gradually by cutting the reed-like stems back to ground level as they appear. This can take several seasons before the plant surrenders and dies back completely. Finally, you can use a systemic herbicide containing triclopyr, which will kill horsetail. It may, however, take multiple applications before you completely eradicate the plant.
It's rare that a homeowner wants to propagate horsetail since containing or eradicating this fast-spreading plant is more often the challenge. However, if you do want to share plants, it is an easy matter to cut away portions of the rhizomatous root clumps and replant them wherever you want. Spring is the best time to perform this action.
Is horsetail easy to care for?
Yes—horsetail is extremely easy to care for. In fact, it is so pervasive, you may actually have the reverse problem and experience issues with controlling the plant.
How fast does horsetail grow?
Horsetail is an extremely fast grower, though you'll notice more of its growth in spread rather than height. It can cover over 100 feet in a single year.
Can horsetail grow indoors?
Growing horsetail indoors is not recommended, mostly due to the plant's quick-spreading nature and need for abundant and constant water.
Riet-Correa, Franklin, Medeiros, Rosane MT., Pfister, James A., Mendonca, Fabio S. Toxic Plants Affecting the Nervous System of Ruminants and Horses in Brazil. Brazilian Journal of Veterinary Research, 37,12,2017, doi:10.1590/S0100-736X2017001200001
Thurston County Noxious Weeds Program. Integrated Pest Management Prescription: Horsetail-Scouring rush. Published online December 2009.
Horsetail and Scouringrush. University of California Weed Research & Information Center.