Ornamental · Equisetaceae
Horsetail
Equisetum hyemale
Handsome, jointed evergreen stems for a soggy corner, as long as you keep it in a container so it can't wander.
Full sun
Every 1–3 days
USDA 3–11
2–4 ft · 0.6–1.2 m
Overview
Horsetail, sometimes called scouring rush, belongs to one of the oldest plant families still with us, a gentle survivor from long before flowers existed. It sends up stiff, jointed, bamboo-like green stems that stay standing all year and never grow a true leaf or a bloom. Instead it multiplies by spores from a small cone at each stem tip and, far more freely, by roots that creep underground.
Gardeners love it as a bold upright accent beside a pond or in a bog bed, where the slim evergreen stems look almost like living sculpture. Those gritty, silica-rich stems earned the old name scouring rush, because people once used them to scrub their pots clean. Best of all, it asks for very little beyond a steady supply of water, so you needn't feel daunted.
The plant does come with two honest cautions, and knowing them is half the battle. Its roots run deep and fast and make it one of the hardest plants to remove once it slips loose, so it truly belongs in a sealed container rather than open soil. It also carries thiaminase, which poisons grazing horses and livestock, so keep it a safe distance from any pasture.
Care
The short version: give it full sun to part shade and soil that never dries out, ideally a pot standing in water, and grow it inside a solid container or barrier so its rhizomes can't run.
Light
Horsetail is happiest in full sun, yet it takes partial sun and even partial shade without any fuss. Plenty of light keeps the stems standing stiff and full, while deep shade leaves them thin and inclined to flop.
Water
This is a bog plant that wants its roots constantly wet, so water every 1 to 3 days and never let the soil dry out. It thrives right at a pond edge, or in a pot standing in shallow water up to about 4 inches (10 cm) deep.
Soil
Settle it into wet to constantly moist, boggy soil and it will be content. It isn't picky about texture, growing in clay, loam, or sand, and it even shrugs off standing water, which suits a plant born at the edges of ponds and streams.
Temperature
Few plants are this tough, which makes it forgiving. Horsetail brushes off cold down to -40°F (-40°C) and takes heat up to around 100°F (38°C), so it settles happily across a huge sweep of climates.
Humidity
It enjoys high humidity, a natural match for the damp, waterside places it calls home. Keep the soil saturated and the moist air around a pond or bog will handle the rest for you.
Feeding
Here's a plant that needs little to no fertilizer, so you can breathe easy. If it lives in a pot, a light balanced feed in spring is plenty, and in the ground it gets by on nothing at all.
Pruning
Trim old or damaged stems right down to the base in late winter or early spring to freshen the clump. Clip off the spore cones before they ripen if you'd like to hold back any spread, and never compost the trimmings or stray bits of rhizome.
Repotting
Give it a fresh start every 1 to 2 years, both to renew the soil and, just as vitally, to keep those pushy rhizomes penned in. When you spot a dense mat of roots filling the pot or stems climbing the rim, that's your cue.
Size & spacing
Stems rise 2 to 4 feet (61 to 122 cm) tall, and a stand will spread 1 to 6 feet (30 to 183 cm) wide if you let it roam. That wandering habit is exactly why it feels right at home in a contained pot or barrier instead of open ground.
When to plant
Horsetail is a hardy perennial that copes from zone 3 to 11, so it happily lives outdoors year-round across most of the country. Set it out in spring once the soil has warmed, and always into a fully contained pot or a bottomless barrier. It won't flower or give you a harvest; instead it raises spore cones from spring into summer.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Plant: Spring, once the soil has warmed; site only in a fully contained pot or bottomless barrier
- Harvest: Non-flowering; produces spores in a cone-like tip (strobilus) in spring to summer
Hardiness
USDA hardiness zones: 3–11
Temperature: down to -40°C
Troubleshooting
Horsetail almost never struggles to grow, which is wonderful news for a first-timer. Your real job is simply keeping it where you put it, so the notes below lean toward gentle containment far more than nursing a poorly plant.
New stems keep popping up far from where you planted
Take heart, because this is easy to manage once you know it. The deep-running rhizome network is the plant's one real weakness, traveling several feet down and sideways, forming colonies, and even slipping out of ponds into nearby wet soil. Every stray fragment can resprout, so digging and sprays seldom finish the job. Give it a solid pot or a bottomless barrier from day one, snip escaping stems as you notice them, and bin every scrap of rhizome you lift.
Fix:
- Never plant loose in open ground; grow only in a solid pot with no drainage to the soil, or in a bottomless barrier sunk into the bed
- Repeatedly cut or pull emerging stems to starve the rhizomes over time
- Remove and destroy (do not compost) every rhizome fragment when digging out an established stand
Stems going floppy, yellow, or thin and sparse
Don't worry, this one is simple to put right. Floppy, pale, thinning growth nearly always tells you the soil got too dry, since horsetail loves steady moisture and sulks the instant its roots dry out. Heavy shade can thin it as well. Keep the soil soaked or stand the pot in water, and shift it into a brighter spot, anywhere from full sun through part shade, and it will bounce right back.
Fix:
- Keep soil constantly wet or stand the pot in water
- Move to a site with more sun (full sun to part shade)
Toxicity
Give this plant a little healthy respect and you'll both do fine. It is truly poisonous to horses and livestock, since the thiaminase it carries destroys vitamin B1 and brings on weakness, staggering, and worse, and it stays toxic even after drying in hay. It isn't a big danger to cats and dogs, but it isn't edible for anyone, so keep it clear of pastures, grazing animals, and inquisitive mouths.
Toxic to
Cats · Dogs · Horses · Rabbits · Livestock · Birds · People
Cats Caution
You can relax about your cat here, since horsetail isn't a known poisoning risk and doesn't appear on the ASPCA toxic list for them. It still isn't food, so gently steer a curious cat away from gnawing the stiff stems.
Dogs Caution
Good news for dog owners: dogs aren't flagged as truly at risk, and the plant isn't listed as toxic to them. A determined chewer might get a mild tummy upset from the gritty, silica-rich stems, so it's kindest to keep it out of reach.
Horses Toxic
Horses need the most care here. The thiaminase in horsetail pulls vitamin B1 out of their system, and a horse that eats enough of it, whether fresh or dried into hay, loses condition and weakens, then begins staggering and trembling, with convulsions and death in the very worst cases.
Rabbits Caution
The thiaminase that troubles bigger grazers is reason enough to keep horsetail well clear of a rabbit's diet. Simply don't offer it, and pull up any that sneaks into a grazing run.
Livestock Toxic
Cattle, sheep, and other grazing animals can develop the very same vitamin B1 deficiency, known as equisetosis. Keep an eye out for weakness, staggering, and poor coordination, with death possible in bad cases, and bear in mind that contaminated hay stays risky long after it has dried.
Birds Caution
The evidence for birds is thin either way, so it's safest to treat horsetail as off-limits rather than assume it's fine. Keep poultry and pet birds away from the foliage and you have nothing to fret over.
People Caution
Please remember this isn't an edible plant, and its thiaminase works against vitamin B1 in people too. Skip any casual nibbling or homemade remedies, and keep little ones from chewing the stems.
Safe to handle and not a significant pet toxin, but keep this plant well away from pastures, grazing horses, and livestock, and never let it contaminate hay; even dried plants in hay retain the thiaminase toxin.
Helpline numbers
United States
ASPCA Animal Poison Control: (888) 426-4435 (fee applies)
Poison Control: (800) 222-1222
Canada
Poison Centres: 1-844-764-7669
Varieties
The genus holds dozens of species, though only a handful tend to show up in gardens and in everyday chats about horsetail.
Equisetum giganteum (giant horsetail)
The towering South American member of the genus, it climbs far higher than the temperate scouring rushes most gardeners know.
Equisetum arvense (field horsetail)
A smaller, branching weed of disturbed soil, it carries the very same thiaminase that makes it toxic to horses and livestock.
Equisetum scirpoides (dwarf scouring rush)
The little one of the bunch, it settles into low clumps of slender, wiry, often curly stems that reach only about a foot tall.
How to propagate
Horsetail multiplies all too easily, which is both a gift and a caution. That same willingness to root from a mere scrap of rhizome is what sends it spreading out of bounds, so propagate it only with containment firmly front of mind.
DivisionEasy
Spring · A few weeks to a season
Splitting the rhizome clumps in spring is refreshingly forgiving, and the pieces settle in within a few weeks to a season, with even tiny fragments rooting happily on their own. That very eagerness is what makes the plant so invasive, so let it guide you. Replant only into a fully contained pot or barrier and destroy any leftover fragments you don't want spreading.
Myths
Horsetail is an easy, harmless little ornamental for the garden.
In truth it ranks among the hardest plants you'll ever try to remove, running on deep rhizomes that escape ponds and shrug off herbicides, and the thiaminase it holds poisons grazing horses and livestock. Keep it in a container and well away from pastures and you can enjoy it with a clear conscience.