Historically these curious, and sometimes invasive, plants have been considered fern allies. Based on sophisticated research, however, their status has been significantly altered (Moran 2004). They are, as it turns out, true ferns, even though to most observers their "leaves" do not look like those of ferns at all. By whatever classification, they always have been ancient plants, dating back to the Carboniferous era of 345 million to 280 million years ago. (At that time they were also huge by comparison. Imagine having them march into the landscape at 20 ft. [6 m] tall.) Fossil records indicate that their early relatives actually had what we consider "leaves" but they along with the plant height have been reduced in size over the millennia.
Structurally, equisetums are designed like stacks of vertical peashooters joined by sheaths and extending like tripods with each new emerging segment smaller than the last. Stems are hollow, green, and furrowed. The collarlike, branch-protecting sheaths of whorled leaf bases vary in size, color, and number of teeth (which are the remnants of the "leaves") all of which are factors in identification. When present, the branches are hairlike extensions of the sheaths. Rhizomes are long-creeping, forming networks that are often deeply buried. Species may be evergreen or deciduous and are frequently dimorphic.
Spores carried in cones are green and consequently short-lived (fortunately). They reproduce eagerly on moist soil and have two types of gametophytes, male and female, an unusual characteristic. Division works well so to propagate, divide and conquer. Multisheathed stem cuttings may also root when plunged into moist sand.
Equisetum comes from the Greek equis, horse, and seta, bristle, referring to the horsetail appearance and common name of those in the genus, such as E. arvense, that have tiers of threadlike branches in bushy whorls. Scouring rush is the popular epithet for the unbranched species. All have a high silica content and have been used over the centuries for scouring pots and pans, and for that matter floors. (As a last resort, I have used it on camping trips for cleaning pots.) It has also been highly valued for the demanding and delicate final precision polishing of specialized wood and metal products including cabinets, pewter, and bones and may still be used for violins today. In the medicine chest the same silica content was valued for its use in compresses to help stem the flow of blood from wounds and to hasten the cure of open sores.
The 15 species of Equisetum occur throughout the world, although primarily in temperate climates. In addition there are many hybrids. They are not particular about soil, but do prefer moisture and sunshine and are often found in abundance in gullies, roadside ditches, and boggy meadows. Tough creatures, they were among the pioneering plants on the flanks of Washington State's Mount Saint Helens following the volcanic eruption of 1980. Some are aggressive and are quite willing to "pioneer" in the garden as well. To prevent invasions, but to enjoy their unique architecture, grow them in containers, please.
Equisetum arvense Common horsetail
Epithet means "of ploughed fields."
Deciduous, 1 to 2 ft. (30 to 60 cm). Zones 1 to 10. Dimorphic.
description: The rhizome is very long-creeping. Short, naked, jointed, baby pink fertile stems are the first to appear in
spring, surviving just long enough to shed spores. Grooved, taller sterile stems are a rich green with 12 to 18 bicolored sheaths made up of 14 or fewer white-tipped brown teeth. Lower sheaths are spaced at 1-in. (2.5-cm) intervals with the distance between the segments becoming smaller approaching the upper portions of the stem. Whorls of green and grooved branching branches extend from the sheaths.
range and habitat: Truly an international species, this is native to and naturalized in Europe, Asia, and North America as well as New Zealand.
culture and comments: Although feathery, this species is weedy and should not be introduced to gardens. Once established, it is very difficult to eradicate. The taller but otherwise similar Equisetum telmateia has more teeth, a key distinction according to the Flora of North America (1993).
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