By Mary Gutierrez

Northwest gardeners may cringe at the suggestion that horsetail (Equisetum spp.) is anything but a rank weed. As it begins poking its feathery stalks through the soil in my garden beds each spring, I’ll admit I have a hard time maintaining objectivity.

One problem with my horsetail is that it’s the wrong kind. Instead of the tall, elegant  hollow stems with knobby joints, mine is the fluffy, feathery kind. What’s the difference? I’m glad you asked…

A Little Background

The genus name, Equisetum, is from the Latin equus, horse, and seta, bristle. The name refers to the coarse roots of Equisetum fluviatile, the water horsetail, not the feathery green foliage you see growing in spring.

The genus Equisetum is then split into two subgenera: Equisetum and Hippochaete. Members of subgenus Equisetum have thin branches emerging from the knobby nodes along their stems. What I have in my garden is the feathery Equisetum arvense, a member of this subgenus.

Members of subgenus Hippochaete are commonly called scouring rushes, and have no branches. These are the horsetails with enough architectural presence to grace the water garden or a container.

What, Exactly, Are They?

Another common name for the equisetums is horsetail fern. Indeed, both plants share a common reproductive strategy: they produce spores instead of seeds.

Horsetails use this primitive method of reproduction because they are, indeed, ancient. Equisetum is the only surviving genus of the class Sphenopsida—a class that included tree-sized horsetails during the Carboniferous period 300 million years ago.

I can imagine a prehistoric forest of Douglas fir-sized horsetails growing in a humid, swampy environment. Earlier this year, I wrote a story about how heron-sized dragonflies populated the earth 250 million years ago. Just as dragonflies perch on stems of horsetail today, in my mind’s eye I can see those giant insects flitting through a horsetail forest.

This prehistoric garden would also be populated by a few other plants still in existence. The cycads—often confused with palms—came along just after the huge horsetails, and were contemporaries of the ginkgo, monkey puzzle (Araucaria spp.), and tree-sized mosses.

Horsetails Today

Depending on which source you consult, there are somewhere around 20 Equisetum species in the world today. A few of them are available to gardeners to grow as a water garden accent or  a container specimen. The popular ones belong to the jointed-grass group in subgenus Hippochaete.

Two species of horsetails are most commonly available for sale at nurseries: Equisetum hyemale, the horsetail rush, which grows two to three feet tall; and Equisetum scorpioides, or dwarf horsetail, which grows to just 10 inches tall.

Horsetails love riverbanks and swampy areas, so are perfectly adapted to the backyard pond. If grown in the pond, keep the crown of the plant above the water’s surface. Any nursery person worth their salt will tell you that equisetum is a great marginal plant—just keep it confined to a pot. Horsetail can spread very rapidly and is classified as an invasive plant in some parts of the country, so don't sink its roots into open soil.

I think a great way to display equisetum is in a striking pot sited on the banks of your water garden. It makes a dramatic focal point at the pond’s edge. When your friends come over to admire your garden and they ask about the distinctive plant growing by the pond, you’ll have lots to tell!  NWGN