Ornamental · Juncaceae
Corkscrew Rush
Juncus effusus 'Spiralis'
Keep its roots wet and never dry, and corkscrew rush spins out a season of glossy, twisting green coils.
Full sun
Every 1–3 days
USDA 4–9
12–18 in · 30–46 cm
Overview
Corkscrew rush is all stem, and every one of them coils. Leafless and smooth, each green shoot springs straight from the crown and winds into loose corkscrew loops, so a mature plant reads as a tangle of bright, spiraling green wires with no flat foliage to break them up. Run a hand through it and the stems feel firm and springy, rounded and solid all the way through.
It is a rush, not a grass or a sedge, and the difference shows in the stems themselves: round and pithy rather than hollow or edged. In summer it carries small, loose clusters of inconspicuous yellowish-green to brown flowers tucked along the upper coils, easy to miss against the green. The stems hold their twist and color through much of the year, a tough, cold-hardy perennial that stays green when many plants brown off.
The coils define the plant, so the stems that count are the curled ones. Now and then it pushes up a plain straight green shoot that stands rigid and unwound, a throwback to its wild parent. Pull those smooth, straight stems as they rise and the looping corkscrew character holds across the whole clump.
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, unwound stems, and divide the clump every few years to keep the coils dense and green.
Light
Full sun draws out the tightest, most sharply wound coils in corkscrew rush, though it still curls under partial sun and partial shade. The brighter the light, the denser and springier the spiral stems come in.
Water
This is the part that matters most: the soil must never dry out, or the coils go limp and brown. Keep it consistently moist to wet, or stand a potted plant in a saucer of water. The stems stay plump and green 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
Those green coils rise from rich, constantly moist to wet soil, and the plant is not fussy about texture, taking clay, loam, or sand alike. A wide pH range from 6.0 to 8.0 suits it, and it grows readily in bog conditions or shallow standing water.
Temperature
The wiry stems are remarkably hardy, holding their twist through cold and heat from -29°F to 100°F (-34°C to 38°C). That toughness lets the coils overwinter outdoors in much of the country without protection.
Humidity
Ordinary humidity is plenty, so there is no figure to hit. What keeps the stems firm and green is wet roots, not damp air, which makes it an easy fit indoors or out.
Feeding
It is a light feeder. A single light spring application of a balanced general-purpose or aquatic-plant fertilizer carries the coils through the season, and overfeeding does the plant no favors.
Pruning
Upkeep is minimal. Through the season, comb out or trim away dead and straight stems so the corkscrew coils stay clean and bright, then cut tatty or browned clumps right back to the ground in late winter to early spring.
Repotting
Divide or repot every 2 to 3 years, or whenever the center of the clump dies out. A bare brown middle, a tightly packed crown, or fewer new coiled stems all show it is time.
Size & spacing
A clump of coils reaches 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 can loop out freely.
When to plant
Corkscrew rush is a hardy perennial that sends up fresh coils on its own each year, so there is no seed-starting calendar. New plants go out in spring once frost danger passes, the small loose flowers appear among the stems in summer, and crowded clumps are divided in spring when the curls thin at the center.
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 stems themselves show them plainly. Dry soil and straight, unwound shoots cover most of what you will see. Match the look below to your plant and act early, while the fix is still simple.
Stems browning and crisping as the plant fades
Green coils fading to dull straw and brittle brown point to dry soil, the surest way to lose this plant. Built for bog and pond margins, it crisps the moment its roots go dry: the once-springy stems turn papery and slump flat. Move it into wet soil at once, set a container in a tray of water, and once the coils plump and green up again, snip the dead brown stems away.
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
After a few years the heart of a clump dies out from the middle, leaving a hollow, brown core encircled by a ring of fresh green coils. The congested crown simply runs out of room at the center. Lift the whole clump in spring, cut away the dead brown middle, and replant the vigorous green outer divisions. Repeated every few years, it keeps the curls dense from edge to edge.
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
Stiff, ruler-straight green stems rising through the coils are reversion, the plant reaching back toward its straight wild parent, common rush. The spiral is a selected form, so a clump pushes up these rigid, vertical shoots that stand apart from the looping ones around them. Cut or pull those straight stems out at the base as they show. When a clump reverts hard, the tightest, most tightly wound pieces are divided off and replanted.
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
For households with animals, corkscrew rush is not poisonous to pets, livestock, or people. It does not appear on the ASPCA toxic-plant lists. A pet that chews the wiry, fibrous coils may bring up a little of the stringy material, but that is the tough texture at work, not any toxin.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
No poison sits inside those wiry green stems, so cats are safe. A cat that gnaws the springy, fibrous coils may bring a few strands back up, but that comes from the tough, stringy texture rather than any toxin.
Dogs None
Dogs are in no danger. The coiled stems are tough and stringy, so a determined chewer might catch a strand at the throat and gag for a moment, yet nothing inside the plant is poisonous.
Horses Safe
Horses are unharmed by it. Wiry rushes like this fringe the wet pasture edges where horses graze, and their green stems hold no toxin.
Rabbits Safe
Rabbits are safe with it. The firm, fibrous coils make better gnawing than grazing, and nothing in their stringy green tissue will hurt a rabbit.
Livestock Safe
Cattle, goats, and sheep are unaffected. Native rushes with the same tough, round stems grow across damp grazing land and pass through livestock without trouble.
Birds Safe
Birds are safe around it. These slender green coils are part of everyday wetland growth, and the plant poses no poisoning risk to them.
People Safe
It is not poisonous to people, children included. The stems are grown to look at, not to eat, so there is no edible part, but a curious nibble on the fibrous coils causes no 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 corkscrew rush selections turn up at nurseries, differing in the height, tightness, and color of their coils. These are the ones worth knowing.
Juncus effusus (common rush / soft rush)
This is the straight wild species, its stems rising as plain, upright green spears, while corkscrew rush is the looping form drawn from it, the very same smooth stems that 'Spiralis' keeps trying to revert toward.
'Unicorn'
Raised at the University of British Columbia, it climbs taller at about 18 inches, its coils wound a little tighter and its stems a deeper, darker green than the standard spiral.
'Big Twister'
This selection throws larger, more pronounced corkscrews, the stems coiling more tightly and twisting harder than those of the ordinary form.
'Blonde Ambition'
A compact, variegated form streaked in blonde-gold, it holds its bright coils to about 6 to 9 inches tall while spreading to roughly 18 inches wide.
How to propagate
There is one dependable way to make more corkscrew rush, and it comes down to splitting the coiled clump at the right moment.
DivisionEasy
Spring · A few weeks to a couple of months
Spring division is the way to make more. Lift the clump and ease apart the pale, knotted rhizomes, then set the most strongly spiraled divisions, the ones with the tightest coils, into soil kept wet. New green shoots curl up within a few weeks to a couple of months. Seed is not worth sowing, since seedlings tend to rise straight and smooth rather than curled.
Myths
Corkscrew rush is an ornamental grass.
It is not a grass at all; it is a rush in the family Juncaceae. The old saying sorts the look-alikes by feel: rushes are round with solid, pithy stems, grasses are hollow and jointed, and sedges have edges with triangular stems. Roll one of these stems between finger and thumb and it turns smooth and cylindrical, packed with soft white pith inside.