Bulb · Colchicaceae
Autumn Crocus
Colchicum autumnale
Bare lilac-pink goblets push up in fall, yet every part hides deadly colchicine.
Full sun
Every 7–14 days
USDA 4–9
6–10 in · 15–25 cm
Overview
Autumn crocus catches the eye in the strangest way. Its lilac-pink, goblet-shaped flowers push straight up out of bare earth in late summer and fall, with not a leaf around them, the trick that earns the name naked ladies. The broad, strappy blades arrive only the following spring, feed the corm, and shrivel away by summer before the next round of bloom.
The name misleads, because this is no kin to the spring crocus you might picture. It sits in the family Colchicaceae and grows from a corm rather than a true bulb, settling in easily along a woodland edge or scattered through a lawn in zones 4 to 9. Plant it once and the clumps widen on their own, year after year.
The danger is the real story. Every part of this plant is packed with colchicine, among the deadliest compounds you will find in any garden, and nothing reverses it once swallowed. Beautiful and simple to grow it may be, yet it draws a hard line between the flower bed and anything that might take a bite.
Care
The short version: sink the corms into well-drained soil in full sun to light shade, water moderately only while the spring blades are up, and let those leaves yellow on their own before clearing them away.
Light
Give autumn crocus full sun for the heaviest flowering, though it puts up with partial shade and rarely sulks. A woodland edge fits it well, since the corm gets open light in spring while the leaves are at work and softer, broken shade later in the year.
Water
Keep the soil at medium moisture while the blades are up in spring, then taper off almost completely as the corms drop into summer dormancy. Sharp drainage is non-negotiable, because standing wet rots the corm quicker than any other threat.
Soil
It roots happily in loam, clay, or sand so long as the ground runs organically rich and well drained. A pH from 6.0 to 7.5 suits it fine, and the single thing that matters above all is that water never pools around the corm.
Temperature
This is a properly cold-hardy plant, settled across zones 4 to 9 and tolerant from roughly -4°F to 75°F (-20°C to 24°C). It wants a spell of winter chill to perform and brushes off hard frost with no cover at all.
Humidity
Plain outdoor air is everything it needs, so there is nothing to gauge or fuss over. What counts far more is keeping the spring blades dry and uncrowded, since damp, packed foliage opens the door to smut.
Feeding
Mix a balanced bulb fertilizer or compost into the soil at planting in fall and that is more or less the whole job. The corm banks its own energy from the spring leaves, so piling on feed buys you little.
Pruning
There is no real pruning here. Let the spring foliage die back on its own so the corm can stock up for the next bloom, and gather the leaves only once they have gone yellow. Never take the leaves off while they are still green.
Repotting
In the ground it calls for dividing rather than repotting, every 3 years or so once clumps grow tight. The cues to watch for are fewer or smaller flowers, jammed-together clumps, and corms muscling their way up to the surface.
Size & spacing
Plants hold low, topping out around 6 to 10 inches (15 to 25 cm) tall with a roughly matching spread. Set the corms 6 inches (15 cm) apart and 3 to 6 inches deep so each one has the room to clump up over the years.
When to plant
Autumn crocus keeps an upside-down schedule. Set the dormant corms out in late summer, around August, and the flowers come up within weeks that same fall. The leaves wait clear through to the following spring, feed the corm, and fade by midsummer ahead of the next bloom.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: Not recommended; seed is slow and usually sown outdoors
- Plant: Plant dormant corms 3-6 inches deep and about 6 inches apart in mid- to late summer (August)
- Harvest: Leafless flower stems bloom August to September (late summer to early fall); broad leaves appear the following spring and die back by summer
Hardiness
USDA hardiness zones: 4–9
Temperature: down to -34°C
Troubleshooting
Autumn crocus is rugged and asks for next to nothing, so most trouble traces back to wet soil, hungry slugs, or the sprawling habit of those bare stems. Match what you are seeing to the list below and step in early. Sharp drainage shuts down the one problem that genuinely kills the plant.
Mushy corms that never break ground
Corm rot takes hold once the soil sits wet and waterlogged for too long. Dig a corm up and instead of crisp, firm flesh you meet soft, browned, sour-smelling pulp. Bin every rotted one and tuck the sound corms back into sharply drained ground or a raised bed, since keeping the corm dry is the only thing standing between you and rot.
Fix:
- Discard rotted corms
- Replant healthy corms in sharply drained soil or a raised bed
Gnawed corms and torn punctures in the fresh shoots
What you are seeing is slug and snail damage, worst in ground that stays damp and shaded. Run a finger near the soil surface and you will find glistening slime trails and soft, scooped-out wounds in the corm flesh. Pick the offenders off by hand after dark or scatter bait, then strip back the mulch pressing on the corms so they lose the cover they shelter under.
Fix:
- Hand-pick slugs and snails at dusk
- Set bait or traps around plantings
- Improve drainage and reduce mulch contact on corms
Swollen dark blisters and sooty smears across the spring blades
Those puffed-up welts that split open and shed a dark, dusty powder are fungal smut riding the foliage. Strip off and burn any leaf showing them the moment it appears. The fungus settles in where the broad blades stay wet and packed together, so give the corms breathing room and steer water away from the leaves.
Fix:
- Remove and destroy infected leaves
- Avoid overhead watering and crowding to improve air flow
Bare flower stems sprawling and sagging to the ground
This is the plant being exactly what it is, not a fault to fix. The lilac-pink goblets ride up on naked, leafless stems in fall, with no blades alongside to prop them, so they lean and spill over once wind or rain hits. Run them up through a low groundcover or tuck them among short perennials and the neighboring foliage cradles the blooms upright.
Fix:
- Underplant with a low groundcover to support stems
- Site among low perennials that hold flowers upright
Toxicity
Read this plant as a poison, never a snack. Every part holds colchicine, with the corms and seeds carrying the heaviest load, enough that even a small bite can kill pets, livestock, and people, often with no sign for hours. There is no antidote, so the only true safety is keeping it out of reach and washing your hands the moment you set it down.
Toxic to
Cats · Dogs · Horses · Rabbits · Livestock · Birds · People
Cats Severe
A cat that mouths any piece of this plant is in genuine peril. Thick drooling and bloody vomiting strike first, then diarrhea, collapse into shock, and harm to the liver and kidneys, with the bone marrow failing later on. Because the signs can hold off for hours, head to the vet on suspicion alone instead of waiting for them to surface.
Dogs Severe
Dogs root out and crunch the corms, the most concentrated part of the whole plant. Look for drooling, bloody vomiting and diarrhea, sudden collapse, and organ failure that may hold off until long after the bite. This poisoning kills more often than not, so treat the smallest nibble as an emergency.
Horses Severe
A horse grazing on autumn crocus is gripped by violent colic and bloody diarrhea, then slides into shock as its organs give out. The colchicine acts the same at horse scale, and the result is deadly more often than not. Phone the vet the instant a mouthful seems possible.
Rabbits Severe
No bite is a safe bite for a rabbit here. The colchicine packed into the leaves, flowers, and corms tears up the gut and drives a fast crash, and a small body has almost no buffer against it. Fence this plant out of every spot a rabbit might reach.
Livestock Severe
Cattle, sheep, and goats fall ill from autumn crocus both in the pasture and in baled hay, where the toxin keeps its bite long after the plant dries. Bloody scouring, weakness, and failing organs set in, and animals can die. The bitter taste turns some grazers away, but hungry stock and tainted hay are where the danger really lies.
Birds Severe
Colchicine poisons birds just as it poisons mammals, and a pecking hen or inquisitive parrot can swallow a lethal dose from a corm or a seed. Expect crop and gut upset, weakness, and a swift downhill slide. Keep birds clear of the plant and any seed it has shed.
People Caution
No piece of autumn crocus is food, and people have died after taking the corms for wild garlic or the plant for true saffron. Swallowing any part can trigger severe vomiting, bloody diarrhea, multi-organ failure, and bone-marrow suppression, with no antidote to fall back on. Even handling it can leave the skin irritated, so pull on gloves and keep it well clear of children.
Keep corms, seeds, leaves, and flowers out of reach of pets and children. Store corms securely, wear gloves when handling as the plant can cause contact dermatitis, and wash hands afterward. Never confuse with culinary saffron.
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 wild species turns up far more than anything else, but one named selection makes its way into gardens.
Pleniflorum
Its flowers come fully double in rose-pink, a packed-petal look set apart from the single, star-shaped lilac-pink blooms of the species.
Companions
Autumn crocus pairs best with plants that prop up its bare flower stems and share its taste for sun in spring and lighter shade later.
Plant near
Low groundcovers: Help support the weak leafless flower stems and keep blooms from flopping
Deciduous shrubs and woodland-edge perennials: Provide a naturalizing setting with full sun in spring when foliage is present and light shade later
How to propagate
Autumn crocus multiplies readily once it has settled in, and the quickest routes all lean on the corm rather than waiting on seed.
Offsets & pupsEasy
Lift in summer after leaves die back · Blooms the following fall once established
Each parent corm buds off little offsets clustered around its base. Dig the clump in summer once the blades have died back, twist the offsets loose, and set them back 3 to 6 inches deep and about 6 inches apart. They take hold quickly and bloom the next fall.
DivisionEasy
Summer after foliage dies back but before flowers emerge; divide every 3 years when crowded · Establishes and blooms the same fall or the next
Once a clump packs in on itself and the flower count drops, lift it and pull it apart. Time this for summer after the foliage has withered but before the flower stems shoulder up, on roughly a three-year cycle. Split corms will often flower that very fall, or else the one that follows.
Bulbs & cormsEasy
Plant dormant corms in mid- to late summer (August) · Flowers the same fall after late-summer planting
Settle dormant corms into the ground in mid- to late summer, around August, and they put up flowers that same fall. Get them planted the day they arrive, because these corms keep poorly in storage and shed their vigor quickly.
SeedModerate
Sow outdoors when ripe · Slow; seed-grown plants take several years to reach flowering size
Seed is the patient route. Sow it outdoors the moment it ripens, then settle in for a wait, since seed-grown plants need several years to reach flowering size. Splitting corms or harvesting offsets brings the blooms along much faster.
Myths
Autumn crocus is just a fall-blooming spring crocus and is equally harmless.
The two are not related at all. Autumn crocus is Colchicum autumnale in the family Colchicaceae, whereas the true spring crocus sits in the genus Crocus within the family Iridaceae. Colchicum is loaded with colchicine in every part and is far more dangerous, and a quick way to separate them is the stamen count: this one carries six to the true crocus's three.
Autumn crocus can be used like saffron in cooking.
Keep every part of this plant nowhere near food. Eating Colchicum autumnale can kill you thanks to its colchicine, while the saffron in your kitchen comes from the entirely separate Crocus sativus. All the two have in common is a passing resemblance.