Ornamental · Juncaceae
Corkscrew Rush
Juncus effusus 'Spiralis'
Keep its roots wet and never dry, and corkscrew rush throws out a season of twisting green coils.
Full sun
Every 1–3 days
USDA 4–9
12–18 in · 30–46 cm
Overview
Corkscrew rush earns its name the moment you see it. Each leafless stem spirals and loops like a green corkscrew, springing straight from the crown in a tight clump with no real leaves to speak of. It's a rush, not a grass or a sedge, and it brings movement to a planting that nothing else quite matches.
What sets it apart from most garden plants is its thirst. This is a bog and pond-margin plant at heart, happiest in ground that stays wet or even in a few inches of standing water. Grow it at the edge of a water feature, in a permanently soggy spot, or in a pot sitting in a saucer of water, and it asks for little else.
It's a tough, cold-hardy perennial that holds its curls through much of the year. The one habit to watch is its tendency to send up plain straight stems, a throwback to its wild parent. Pull those as they appear and the spiral character stays front and center.
Care
The short version: full sun to part shade, soil that never dries out, and a wet or boggy spot it can sit in all season. Cut out any straight reverted stems, and divide the clump every few years to keep it fresh.
Light
Give corkscrew rush full sun for the best, tightest curls, though it takes partial sun and partial shade without complaint. More light generally means denser, more vigorous spiral growth.
Water
This is the part that matters most: the soil must never dry out. Keep it consistently moist to wet, or stand a potted plant in a saucer of water. It's happy in boggy ground and even in standing water up to a few inches over the crown, so check moisture every day or two in warm weather.
Soil
It grows in rich, constantly moist to wet soil and isn't fussy about texture, handling clay, loam, or sand alike. A wide pH range from 6.0 to 8.0 suits it, and it does well in bog conditions or shallow standing water.
Temperature
Corkscrew rush is remarkably tough, riding out cold from -29°F to 100°F (-34°C to 38°C). That cold hardiness lets it overwinter outdoors in much of the country without protection.
Humidity
Ordinary humidity is plenty, so there's no figure to hit. What the plant cares about is wet roots, not damp air, which makes it an easy fit indoors or out.
Feeding
It's a light feeder. A single light spring application of a balanced general-purpose or aquatic-plant fertilizer carries it through the season, and overfeeding does it no favors.
Pruning
Upkeep is minimal. Through the season, comb out or trim away dead and straight reverted stems to keep the corkscrew look sharp, then cut tatty or old clumps right back to the ground in late winter to early spring.
Repotting
Plan to divide or repot every 2 to 3 years, or whenever the center of the clump dies out. A bare middle, a congested crown, or fewer new spiraled stems all tell you it's time.
Size & spacing
Clumps reach about 12 to 18 inches (30 to 46 cm) tall and just as wide. Give each plant a matching 12 to 18 inches (30 to 46 cm) of room so the spiraling stems have space to show.
When to plant
Corkscrew rush is a hardy perennial that comes back on its own, so there's no seed-starting calendar to keep. Set new plants out in spring once frost danger has passed, watch for the loose summer flowers, and divide established clumps in spring when they need refreshing.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Plant: Spring after frost danger passes
- Harvest: Inconspicuous yellowish-green to brown flowers in loose cymes, summer (roughly June to September)
Hardiness
USDA hardiness zones: 4–9
Temperature: down to -34°C
Troubleshooting
Corkscrew rush has few troubles, and the ones it does have are easy to read. Dry soil and straight reverting stems cover most of what you'll meet. Match the sign below and act early, while the fix is still simple.
Stems browning and crisping as the plant fades
Dry soil is the single most common way to kill this plant. A rush is built for bog and pond margins, so the moment the ground dries the stems brown, crisp, and collapse. Move it to wet soil at once, stand a container in a tray of water, and trim out the dead stems once it perks back up.
Fix:
- Move to consistently moist or wet soil immediately
- Stand container in a saucer or tray of water, or place at a pond/bog edge
- Keep soil saturated; the plant tolerates standing water up to a few inches over the crown
- Trim out dead browned stems once moisture is restored
A dead, hollow center ringed by healthy growth
Older clumps die out from the middle as the crown gets congested over a few years, leaving a live outer ring around a bare heart. Lift the whole clump in spring, throw away the spent center, and replant the strong outer divisions. Doing this every few years keeps the plant young.
Fix:
- Lift and divide the clump in spring
- Discard the dead central portion and replant vigorous outer divisions
Straight green stems pushing up among the curls
This is reversion, the plant sliding back toward its straight wild parent, common rush. The spiral form is a selection, and a clump will throw rigid, vertical stems if you let it. Cut or pull those stems out at the base as they show, and divide and replant the most tightly curled pieces if a clump reverts hard.
Fix:
- Cut or pull out the straight reverted stems at the base as they appear
- Remove reverted growth promptly and repeatedly to keep the corkscrew appearance
- If a clump reverts heavily, divide and replant the most strongly spiraled portions
Toxicity
Good news for households with animals: corkscrew rush is not poisonous to pets, livestock, or people. It doesn't show up on the ASPCA toxic-plant lists. A pet that chews the wiry stems might cough up a bit of fiber, but that's about the texture, not any toxin.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
Safe to have around cats, with no poison in the stems. A cat that chews on the wiry stems might bring up a little of the fiber, but that's a texture problem, not a toxic one.
Dogs None
No danger to dogs. The fibrous stems can scratch at the throat of a determined chewer and trigger a quick gag, yet nothing in the plant is poisonous.
Horses Safe
Harmless to horses. Rushes like this grow in the wet pasture edges where horses graze, and they carry no toxin.
Rabbits Safe
Safe for rabbits. The tough, fibrous stems are more chew toy than meal, and there's nothing in them that will hurt a rabbit.
Livestock Safe
No concern for cattle, goats, or sheep. Native rushes turn up in damp grazing land and pass through livestock without trouble.
Birds Safe
Safe around birds. Rushes are a familiar part of wetland habitat, and the plant poses no poisoning risk to them.
People Safe
Not poisonous to people, including children. The plant isn't grown to eat, so there's no edible part to offer, but a curious nibble won't cause harm.
Generally safe around pets and people; pets that nibble the stems may occasionally vomit from the fibrous material, but the plant is not poisonous.
Varieties
A few named selections of corkscrew rush turn up at nurseries, differing mostly in size, curl, and color. These are the ones worth knowing.
Juncus effusus (common rush / soft rush)
This is the straight wild species with upright green stems, and corkscrew rush is the curled form selected from it, the same plain stems that 'Spiralis' tries to revert toward.
'Unicorn'
Bred at the University of British Columbia, it stands taller at about 18 inches with slightly tighter curls and a darker green than the standard spiral form.
'Big Twister'
This selection is grown for its larger, more pronounced curling stems that twist harder than the ordinary form.
'Blonde Ambition'
A compact, variegated pick with blonde-gold foliage, staying around 6 to 9 inches tall while spreading to about 18 inches wide.
How to propagate
There's really only one good way to make more corkscrew rush, and it's quick and reliable once you know the timing.
DivisionEasy
Spring · A few weeks to a couple of months
Divide it in spring by lifting the clump and pulling the rhizomes apart, then replant the most strongly spiraled divisions into soil you keep wet. A fresh division settles in within a few weeks to a couple of months. Skip growing it from seed, since seedlings often come up straight rather than curled.
Myths
Corkscrew rush is an ornamental grass.
It isn't a grass at all, it's a rush, in the family Juncaceae. The old saying sorts it out fast: rushes are round with solid, pithy stems, grasses are hollow and jointed, and sedges have edges with triangular stems.