Louis Raymond experiments in his own gardens like

a mad scientist, searching out plants that most people have

never seen before & figuring out how to make them perform.- The Boston Globe

…Louis Raymond ensures that trees can grow in Brooklyn…

or just about any other place where concrete consumes

the dirt and skyscrapers shield the sunshine.- USA Today

 
 

NEW Trips to Take!

Myrtle's easy when the conditions are right.

 
 
 
 

NEW Plants to Try!

Louis tries to capture the exact words to describe the fleeting but deep pleasures to be found in these Summer-into-Autumn incredibles.

 
 
 
 

New Gardening to Do!

Allergic to bees? You can still have an exciting garden, full of flowers and color and wildlife.

 
 
 
 

Plant Profiles

Giant Scouring Rush

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Stems of scouring rush have a unique simplicity of design, a sparsity of detail. Seemingly without leaves or branches, and with a regularity in the horizontal banding that suggests a secret mathematical formula, Equisetum hyemale marches to its own drummer.

 

The horizontal bands look like crochet work, or ribbon that has been carefully "pinked" on the bottom and fringed on the top. Those small filaments are actually the plant's leaves; clearly, the real business of photosynthesis is carried out by the green stems themselves.

 

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My young colony is still filling out its tub; more mature stands pack their containers with coiling rhizomes that support a tight broom-like sheaf of vertical green stems.

 

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Scouring rush is unusually hardy, and thrives when planted directly in any garden south of the Arctic Circle—or when growing year-round in a water-tight container that sits out in the garden. I've overwintered my colony in the greenhouse to speed up growth. Stems of mature colonies of Equisetum hyemale var. robustum can be six feet tall; at three feet, my colony is just beginning to display its vertical flourish.

 

Here's how to grow this unusually sculptural and hardy perennial:

 

Latin name

Equisetum hyemale var. robustum

Common name

Giant scouring rush

Family

Equisetaceae, the Horsetail family.

What kind of plant is it

Prehistoric relative of ferns, but looking like a grass or rush. Evergreen in frost-free climates; herbaceous otherwise.

Hardiness

Zones 3 to 11.

Habit

Dense stands of vertical stems in quickly-spreading colonies.  

Rate of growth

Fast.

Size in ten years

Five to eight feet tall, depending on mildness of the climate and availability of water; lateral spread is aggressively indefinite unless the roots are contained. 

Texture

Striking tight growth of vertical stems.

Grown for

its peculiar hollow stems, which are bright green and appear to be leafless. (There are true leaves, but they are reduced to regular rings of small deep-eggplant frills.) Colonies of Equisetum tend to grow very densely—so much so that their numerous stems crowd out other plants. The result is a strikingly pure display, a single-minded celebration of verticality.

 

its nearly alarming toughness. Equisetum thrives from near-Arctic conditions to purely tropical; you can see the same species thriving in Quebec as well as Brazil. Growth is persistent in fairly dry and lean soils, and also in permanently-saturated mud. You'll see Equisetum between railroad ties that are set atop a gravel berm, as well as in in meadows or lawn, or on the banks and in the shallows of ponds and swamps.

 

its ability to survive in containers. The rhizomes of Equisetum are unusually aggressive in the wild, traveling deeply as well as widely; happily, the plant is also successful in the extremely confined root runs of containers. In the garden, it is grown as the sole occupant of a container of water-saturated soil; over time, its rhizomes will crowd the soil as tightly as the vertical stems they produce crowd the above-ground space.

 

its imperviousness to mammalian browsers: The stems are fibrous, and have an unusual sandpapery surface (see "Quirks," below). Deer and rabbits will not be tempted. Caribou are a notable exception, but few of us are gardening near the Arctic Circle.

Flowering season

Horsetails are so old they (like their relatives, the ferns) antedate flowers. Reproduction is by spores, which are produced by pale yellow cone-like structures known as strobili, which emerge at the tips of some of the stems. They are not showy enough to be a factor in the decision to grow Equisetum

Color combinations

Stems of Equisetum hyemale are bright green, with regular horizontal rings so dark an eggplant that they appear black. The occasional yellow strobili are the only other color in the mix, but they are not so numerous or prominent that they would limit the colors of companion plants.

Partner plants

Although Equisetum is too aggressive to be planted where it can grow in the same planting area as neighboring plants, when grown in an escape-proof container, an Equisetum colony can safely be placed amid them. Its stems' verticality and density create a strong contrast to plants with broader habit or prominent foliage. In a larger aquatic context, Equisetum could partner with the same plants that are compatible with other strongly-vertical aquatics such as white rush, pond sedge, papyrus, or cat-tail.

Where to use it in your garden

Because colonies of Equisetum hyemale quickly become dense and impressively tall, they also have enough presence to work without partner plants, as soloists in the same way as colonies of papyrus, cat-tail, or white rush. Any of these plants make a striking vertical statement as they erupt cleanly from the placid open water of a large pond or reflecting pool.

 

While those other "aquatic verticals" also spread impressively, even alarmingly—and, hence, are also best grown in containers from which they can't readily escape—the unusual drought tolerance of Equisetum gives it additional flexibility in its siting. Containers of all the other plants need to be shallowly submerged in a larger volume of water, such that there is no danger that the colony will dry out. (Yes, the downside is that the submergence enables these plants' outward-bound rhizomes to explore into the surrounding open water via the top of the colony's root mass.) Equisetum is unique in not requiring that its container be submerged in that larger volume of water. Thanks to the unusual tolerance of Equisetum for both dry soil and wet, its container can be the totality of the available water garden at its disposal.

 

It is a cliché in mild-climate gardening, especially in a modern or "hip" setting, to use window-box-sized containers of Equisetum to form a living fence that, for example, separates sidewalk cafe tables from the adjacent public sidewalk. Or even to run boxes of Equisetum atop a wall to extend its height. Although these plantings need regular watering, judging by their prevalence, they can endure with enough enthusiasm to be cost-effective in such large and low-maintenance commercial settings. Similar plantings of, say, Papyrus, would be much more expensive as well as ephemeral: They would dry out in hours and fail completely in days.

 

In ornamental gardening, a solo container of Equisetum can be submerged in a water garden or set by itself on a terrace. In the former case, the container need only be a black plastic tub. In the latter, plant directly in a pleasing cachepot, or set the plastic tub in it. 

 

Light that strikes the stems from the side (as would be the case with early-morning or setting sun) is refracted within the hollow stems, causing them to glow like Japanese lanterns. If possible, take advantage of this quirky talent by siting a cachepot'd container of Equisetum at a height where the "stem glow" is at eye level: on an outdoor plinth or atop a wall or table. The Equisetum will need to be roughly between the light source and the viewer, so if siting on a terrace, the Equisetum container will need to be towards its outer edge.

 

Yet another tactic would be to rig up a hidden source of uplighting within the colony itself. Depending on the angle of the lighting, stems might glow from within, or would be highlighted from the light that strikes them but remains external. If automatically watered, such a container of lighted Equisetum could be the theatrical capital of a column. An allée of such columns could be part of the shameless drama of a Las Vegas resort or out-of-control estate. In a more intimate setting, a solo Equisetum-topped column would be a humorous coup de théâtre.

Culture

Sun, in almost any soil. Growth is denser and taller in moist soils—but also more quickly spreading if not controlled.

How to handle it: The Basics

Plant in a water-tight container, in other words, one whose sides and bottom are without any openings. Rhizomes of Equisetum can burrow more deeply than any control measure that is just a vertical barrier, as might work for bamboo. The comparable shallowness of bamboo rhizomes is partly because they don't tolerate soil that is permanently waterlogged, which is more likely to be the case the deeper the rhizomes grow. The rhizomes of Equisetum are fully comfortable in saturated soil, so lack bamboo's inhibition about roving deeply underground.

 

Equisetum is so hardy that it can be planted any season the ground is workable. It is also so hardy it can also be grown in containers that do not receive any Winter shelter, in which case the entire colony, rhizomes as well as stems, could freeze solidly night after night. That said, growth will be more vigorous when the container is not so exposed. Shelter containers of Equisetum by sinking into shallow water of a pond or water feature that doesn't freeze to the bottom, or by bringing the container into frost-free conditions.

How to handle it: Another option—or two?

If growing Equisetum in a stand-alone cachepot, top up the pot daily with water. If your container of Equisetum is one element of a water garden, set it in water at least an inch deeper than the height of the container, so that water will continually saturate the soil of the containered Equisetum. The container can be set much deeper if that's more convenient, as long as the majority of the height of the stems remains above water. 

 

Stems of Equisetum hyemale will be killed back as cold weather settles reliably below freezing. Cut them off at just below the water level any time or season that's convenient; Equisetum is so hardy that you don't need to show it seasonal consideration by, say, waiting until early Spring to do such grooming.

Any (other) quirks or special cases?

The hollow stems appear to glow from within, like Japanese lanterns, when struck by low morning or afternoon sun. See "Where to use it in your garden" for suggestions.

 

The common name, scouring rush, is derived from the stems' coating of microscopic protuberances composed largely of silica. The stems' fibrous nature makes them oddly durable; the protuberances enable the stems to be used as a naturally-occurring Brillo pad to clean and even polish both wood and metal. The small size of the protuberances yields a smoother and more reflective surface than possible with most other polishing options, man-made or not.

Downsides

Equisetum hyemale succeeds in any climate zone warmer than that at the Arctic Circle—and can grow in dry ground as well as wet. This plant's outward march, then, is not stopped by extremes of temperature or water. Do not let Equisetum escape confinement. It is famously difficult to eradicate, either by digging (the rhizomes are very deep—those of E. telmateia have been reported to penetrate several meters—and resprout diligently) or by poisoning (the rhizomes are resistant to most glyphosphate-based herbicides, such as "Round Up").

 

The tight growth of the vertical stems makes Equisetum colonies a tempting target for a flat-top pruning, such that their tops form a single plane. Alas, the stem tips eventually turn an unattractive brown, which can only be rectified by a next round of pruning, to a height an inch or so shorter than before. Those newly-exposed cuts turn brown in time, too, so the pruning cycle (or curse) will continue. Resist the urge to flat-top your Equisetum colony!

Variants

After so many millions of years, this species' lack of variation is astonishing. 'Robustum' is the only variant usually available, and is similar to the species in every other way except its greater height.

 

Other hardy species and forms of Equisetum can be difficult to distinguish from E. hyemale, or from each other. E. hyemale var. affine is about half the height of E. hyemale; E. scirpoides is truly dwarf, remaining shorter than one foot. E. x ferrissii is a natural sterile hybrid of E. hyemale and E. laevigatum, and is intermediate in height between the two. E. fluviatile is exclusively aquatic. Despite its name, E. variegatum isn't noticeably different from the rest, let alone "variegated" in any normally-apparent sense.

 

In short, few gardeners would ever need to grow more than one kind of hardy Equisetum. The subtropical kinds, though, are another story. E. giganteum lives up to its name: Colonies can exceed ten feet in height. E. giganteum 'El Tabacal' is reported as unusually hardy, into Zone 8; I'll profile this cultivar later in 2013. Stems of E. myriochaetum are taller still, with reports of growth exceeding twenty feet; it is more tender than E. giganteum.

 

Availability

On-line and at retailers that sell aquatics.

Propagation

By division.

Native habitat

Equisetum hyemale is cosmopolitan, native to every continent but Antarctica.     

 
 
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