Ornamental · Equisetaceae
Horsetail
Equisetum hyemale
Cool, jointed evergreen stems for a soggy spot, as long as you keep it in a container so it can't take off.
Full sun
Every 1–3 days
USDA 3–11
2–4 ft · 0.6–1.2 m
Overview
Horsetail, which you'll also hear called scouring rush, goes way back, all the way to before flowers were even a thing, which makes it one of the oldest plant lines still around. It puts up stiff, jointed, bamboo-like green stems that stay standing all year and never grow a real leaf or a flower. Instead it spreads by spores from a little cone at each stem tip and, a lot more energetically, by roots that creep underground.
Gardeners love it as a bold upright accent by a pond or in a bog bed, where those slim evergreen stems almost look like living architecture. Ever wonder how it got the name scouring rush? The gritty, silica-rich stems were once used to scrub pots clean. And honestly, it asks for next to nothing beyond a steady supply of water.
Here's where it gets serious, though, on two fronts. Its roots run deep and fast, and that makes it one of the hardest plants to get rid of once it slips free, so it really needs a sealed container, not open ground. It also carries thiaminase, which poisons grazing horses and livestock, so keep it well clear of 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's happiest in full sun, but it'll take partial sun and even partial shade without any complaints. Give it plenty of light and the stems stand stiff and dense, while deep shade leaves them thin and floppy.
Water
It's a bog plant, so it wants its roots constantly wet. Water every 1 to 3 days and never let the soil dry out. It's happiest right at a pond edge, or in a pot standing in shallow water up to about 4 inches (10 cm) deep.
Soil
Give it wet to constantly moist, boggy soil and it's set. It's not fussy about texture, so clay, loam, or sand all work, and it even handles standing water, which makes sense for a plant that lives at the edges of ponds and streams.
Temperature
Not many plants are this tough. Horsetail shrugs off cold down to -40°F (-40°C) and takes heat up to around 100°F (38°C), which is why it does well across such a huge range of climates.
Humidity
It likes high humidity, which is no surprise for something that grows in damp, waterside spots. Keep the soil saturated and the moist air around a pond or bog handles the rest.
Feeding
This is an easygoing plant that needs little to no fertilizer. If it's in a pot, a light balanced feed in spring is plenty, and in the ground it gets by with nothing at all.
Pruning
Cut old or damaged stems right back to the base in late winter or early spring to tidy things up. Snip off the spore cones before they ripen if you want to slow any spread, and never compost the trimmings or stray bits of rhizome.
Repotting
Repot it every 1 to 2 years to freshen the soil and, just as importantly, keep those pushy rhizomes penned in. When you spot a dense mat of roots filling the pot, or stems climbing over the rim, that's your cue.
Size & spacing
The stems stand 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. That wandering habit is exactly why it belongs in a contained pot or barrier instead of open ground.
When to plant
Horsetail's a tough perennial that's hardy from zone 3 to 11, so it can live outside year-round across most of the country. Pop it in during 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 crop, but it does push up 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
Honestly, horsetail rarely has any trouble growing. The real job is keeping it where you put it, so the notes below lean way more toward containing its spread than nursing a sick plant.
Stems showing up nowhere near where you planted them
So here's the catch that trips everyone up: an aggressive, deep-running rhizome network that can travel several feet down and out, build whole colonies, and slip out of a pond into the wet ground around it. And any bit left behind? It just resprouts, which is why digging and sprays usually don't cut it. Keep it in a solid pot or a bottomless barrier, snip off any escaping stems as soon as you spot them, and get rid of every last scrap of rhizome you dig up.
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
Seeing weak, floppy stems? Nine times out of ten it just means the soil went dry, and horsetail really doesn't like that, since it sulks the moment its roots dry out. Too much deep shade thins it out as well. Keep the soil soaked or stand the pot in water, then nudge it into a brighter spot, anywhere from full sun to part shade, and it'll perk back up.
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 one some respect. It's truly poisonous to horses and livestock, because the thiaminase it carries wipes out vitamin B1 and brings on weakness, staggering, and worse, and it stays toxic even after it dries in hay. It isn't a big deal for cats and dogs, but it isn't edible for anyone, so keep it away from pastures, grazing animals, and curious mouths.
Toxic to
Cats · Dogs · Horses · Rabbits · Livestock · Birds · People
Cats Caution
Cats aren't really at risk here, and horsetail isn't on the ASPCA toxic list for them either. That said, it's not food, so it's worth keeping a nibbly cat from chewing those stiff stems.
Dogs Caution
Dogs aren't flagged as being in any real danger, and the plant isn't listed as toxic to them. A dog that chews the gritty, silica-rich stems might get a bit of a stomach upset, though, so it's easiest to just keep it out of reach.
Horses Toxic
Horses are the ones to really worry about. The thiaminase in horsetail pulls vitamin B1 right out of them, and if a horse eats enough, fresh or dried in hay, it loses weight and gets weak, then starts staggering and trembling, with convulsions and even death in the worst cases.
Rabbits Caution
That same thiaminase that hits bigger grazers? It's reason enough to keep horsetail well out of a rabbit's diet. Don't offer it, and pull up anything that creeps into a grazing run.
Livestock Toxic
Cattle, sheep, and other grazing animals get the exact same vitamin B1 deficiency, which goes by the name equisetosis. Keep an eye out for weakness, staggering, and shaky coordination, with death possible in bad cases, and don't forget that contaminated hay stays risky long after it dries.
Birds Caution
For birds, there just isn't much clear evidence one way or the other, so it's smarter to treat it as off-limits than to assume it's fine. Keep poultry and pet birds away from the foliage.
People Caution
This one isn't an edible plant, and its thiaminase works against vitamin B1 in people too. So skip the casual nibbling and home remedies, and keep kids 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
There are dozens of species in the genus, but only a handful really come up in gardens and in chats about horsetail.
Equisetum giganteum (giant horsetail)
It's the big South American cousin of the group, and it stands way taller than the temperate scouring rushes you'll usually see.
Equisetum arvense (field horsetail)
It's a smaller, branching weed of disturbed ground, and it's got the same thiaminase that makes it toxic to horses and livestock.
Equisetum scirpoides (dwarf scouring rush)
It's the tiny one, forming low clumps of slender, wiry, often curly stems that only reach about a foot tall.
How to propagate
Horsetail multiplies all too easily, which is both good and, well, a bit of a headache. That same knack for rooting from a scrap of rhizome is what sends it spreading out of bounds, so only propagate it with containment already sorted.
DivisionEasy
Spring · A few weeks to a season
Just split the rhizome clumps in spring and the pieces settle in within a few weeks to a season, and even tiny fragments will root all on their own. Handy, right? Well, that same eagerness is exactly what makes it so invasive. Only ever replant into a fully contained pot or barrier and destroy any fragments you don't want.
Myths
Horsetail is an easy, harmless little ornamental for the garden.
Not quite, because it's actually one of the toughest plants you'll ever try to shift, spreading on deep rhizomes that escape ponds and laugh off herbicides, and the thiaminase it carries poisons grazing horses and livestock. Keep it in a container and well away from pastures.