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 the stems are skinny, like tall grass, and it reproduces through spores (not seed), like ferns, as well as underground rhizomes. However, horsetail is not related to bamboo or grass or ferns. Its species dates back to Paleozoic times, some 350 million years ago. 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, similarly to ornamental grasses.
Horsetail spreads via rhizomes and spores and 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); most plants classified as invasive are not native. So it is more accurate (in a North American context) to describe horsetail plants as aggressive spreaders. 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.
Botanists point out that Equisetum hyemale has tiny leaves fused onto its stems. But the untrained eye notices only the attractive stems, which grow anywhere from 2 to 6 feet tall, depending on conditions. These stems are dark green at times (picking up some bronze color in winter) and hollow. Tiny ridges run vertically along the stems and contain silica, giving them the rough feel that earns the plant the common name, rough horsetail. Early Americans used this plant for scouring pots and pans.
|Botanical Name||Equisetum hyemale|
|Common Name||Horsetail, rough horsetail, scouring rush|
|Plant Type||Evergreen perennial|
|Mature Size||2 to 6 feet tall and 1 to 6 feet wide|
|Sun Exposure||Full sun to part shade|
|Soil Type||Moist, well-drained|
|Soil pH||6.5 to 7.5|
|Bloom Time||Non-flowering plant|
|Flower Color||Non-flowering plant|
|Hardiness Zones||4 to 9|
|Native Area||North America, Eurasia|
How to Grow Horsetail
Far from being fussy plants, often the challenge with horsetails isn't in growing them but in containing them and keeping them from spreading to places where you don't want them to grow. They are born colonizers with 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 plants, such as in a swale, the spreading ability of horsetail is desirable.
To contain horsetail planted in the ground, you can 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 spreads not only by underground rhizomes but also spores, containment is challenging.
Horsetail is extremely adaptable to various light levels, growing in full sun to part shade, but preferring deep shade.
In terms of moisture level in the soil, horsetail prefers a soil that is at least moderately wet. It can even grow in standing water up to a depth of about 4 inches. It's well-suited for rain gardens.
Horsetail prefers poor, sandy, gravely soil. The more fertile the soil, the slower it grows. When growing horsetail in a container, consider adding gravel or sand to potting mix to give it the perfect medium it enjoys.
Temperature and Humidity
Horsetail plants prefer high humidity for several hours a day and thrives in low light. Winter care is not a concern, as it is hardy to USDA zones 3 to 11, although the bright green of the stems may fade during cold winters.
In general, horsetail plants do not like particularly rich or fertile soil, so fertilizing should not be necessary.
Varieties of Horsetail Plants
Another species of horsetail is Equisetum arvense, commonly known as field horsetail or corn horsetail. This is generally categorized as a weed because it is every bit as aggressive as Equisetum hyemale but lacks its redeeming aesthetic qualities.
E. arvense is a true horsetail that bears many branches in a whorled pattern, giving this weed a bushy appearance that resembles a horse's tail. It's also reminiscent of the undersea plant, maiden's hair (Chlorodesmis). 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. It is usually a shade of green lighter than that of E. hyemalis.
Many landscapes become overrun with field horsetail, often growing from a rhizome of the weed that was hidden in some loam or fill that had been brought onto the property in years past. Field horsetail will spread even under dry conditions.
In addition to field horsetail, there are many plants in the Equisetum genus, some of which wild-plants enthusiasts might be interested in growing as ornamental oddities, including:
- Giant horsetail (E. giganteum) is a Central- and South-American native hardy only to zone 8b. Grow it in full sun to partial sun. Its selling point is that it can become 10 feet tall or more.
- Variegated horsetail (E. variegatum), by contrast, is a shorter (6 to 18 inches), hardier plant, being 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. Grow it in sun to partial shade.