Bulb · Colchicaceae
Autumn Crocus
Colchicum autumnale
It sends up bare lilac-pink blooms in fall, yet every part conceals deadly colchicine.
Full sun
Every 7–14 days
USDA 4–9
6–10 in · 15–25 cm
Overview
Autumn crocus surprises everyone who meets it. The lilac-pink, goblet-shaped flowers push up straight from bare earth in late summer and fall, not a leaf anywhere around them, which is how it picked up the name naked ladies. Broad strappy foliage arrives the following spring, fuels the corm, and dies back by summer ahead of the next flush of bloom.
The name misleads, because it shares no kinship with the spring crocus you may already grow. This one belongs to the family Colchicaceae and rises from a corm rather than a true bulb, settling in happily along a woodland edge or sprinkled through a lawn in zones 4 to 9. Plant it just once and it widens into bigger clumps season after season.
Here is the serious catch. Every part of this plant carries colchicine, one of the deadliest compounds you could grow, and nothing reverses it once it's swallowed. The flower is lovely and the plant is easy to grow, yet it demands a firm wall between the bed and anything that might take a bite.
Care
The short version: set the corms in full sun to light shade in well-drained soil, water them at a medium level only while the spring leaves are standing, and let those leaves yellow on their own before you clear them away.
Light
Hand autumn crocus full sun and it flowers at its strongest, though it copes with partial shade without much fuss. A woodland edge fits it beautifully, serving open light in spring while the leaves are at work and dappled shade as the year rolls on.
Water
Keep the soil at medium moisture while the foliage stands in spring, then ease off almost completely as the corms drift into summer dormancy. Sharp drainage is non-negotiable, since waterlogged ground rots the corm quicker than anything else can.
Soil
It thrives in loam, clay, or sand provided the ground is organically rich and well drained. A pH from 6.0 to 7.5 keeps it happy, and the single thing that matters most is that water never lingers around the corm.
Temperature
This one shrugs off cold, settling in across zones 4 to 9 and weathering roughly -4°F to 75°F (-20°C to 24°C). It demands winter chill to perform and laughs off hard frost with no protection at all.
Humidity
Plain outdoor humidity is everything it asks, so nothing here needs measuring or managing. What counts far more is keeping the spring leaves dry and well spaced, because damp, crowded foliage opens the door to smut.
Feeding
Mix a balanced bulb fertilizer or compost into the soil at planting in fall and you are basically finished. The corm banks its own energy from the spring leaves, so piling on more food buys you little.
Pruning
There is nothing real to prune. Let the spring foliage die back on its own so the corm can load up for the next bloom, and sweep the leaves away only once they have yellowed. Never slice into the leaves while they are still green.
Repotting
In the ground it calls for dividing rather than repotting, every 3 years or so as clumps grow crowded. The tells to watch for are fewer or smaller flowers, packed clumps, and corms muscling their way up to the surface.
Size & spacing
Plants keep low, climbing to roughly 6 to 10 inches (15 to 25 cm) tall with a matching spread. Tuck the corms 6 inches (15 cm) apart and 3 to 6 inches deep so each one has the room to bulk up into a clump over the years.
When to plant
Autumn crocus marches to a strange calendar all its own. Set the dormant corms out in late summer, around August, and the flowers chase them up within weeks that same fall. The leaves wait until the following spring, power up the corm, and fade by midsummer just before bloom returns.
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 hardy and asks for next to nothing, so almost every snag traces back to soggy soil, hungry slugs, or the natural flop of its bare stems. Spot what you see below and jump on it early. Sharp drainage knocks out the one trouble that can truly kill the plant.
Mushy corms that sit dead and never push up
Soil that stays wet and waterlogged invites corm rot. Dig one up and the flesh turns mushy, discolored, and foul-smelling rather than firm and solid. Toss every corm that has gone soft, then move the survivors into sharply drained ground or a raised bed, since dry feet are your entire line of defense here.
Fix:
- Discard rotted corms
- Replant healthy corms in sharply drained soil or a raised bed
Gouged corms and torn holes punched into fresh shoots
Damp, shaded ground draws slugs and snails, and they go after the corms and tender new growth fastest. Hunt for slime trails and soft, scooped-out patches on corms sitting near the surface, then pick the offenders off by hand at dusk or lay down bait. Sharpen the drainage and pull back any mulch crowding the corms to strip away the shelter they crave.
Fix:
- Hand-pick slugs and snails at dusk
- Set bait or traps around plantings
- Improve drainage and reduce mulch contact on corms
Sooty streaks and dark blisters breaking out on spring leaves
Swollen blisters that split open into dark, powdery spores point straight to fungal smut riding the foliage. Snap off and burn any leaf you catch infected the second it appears. Crowded, perpetually damp leaves let the disease dig in, so give the corms breathing room and steer water clear of the foliage.
Fix:
- Remove and destroy infected leaves
- Avoid overhead watering and crowding to improve air flow
Bare blooms tipping and sprawling across the ground
Nothing is wrong here; this is simply how the plant grows. Fall flowers shoot up on naked, leafless stems with no foliage beneath to prop them, so a gust or a downpour sends them sprawling. Tuck the corms into a low groundcover or among short perennials, and that surrounding growth cradles the blooms and holds them tall.
Fix:
- Underplant with a low groundcover to support stems
- Site among low perennials that hold flowers upright
Toxicity
Handle this plant as a poison, never a snack. Colchicine fills every part, with the heaviest load in the corms and seeds, and even a small bite can prove fatal to pets, livestock, and people, often with no warning for hours. No antidote exists, so real safety comes down to keeping it out of reach and washing your hands the moment you finish handling it.
Toxic to
Cats · Dogs · Horses · Rabbits · Livestock · Birds · People
Cats Severe
One bite of any part puts a cat in genuine peril. Heavy drooling and bloody vomiting strike first, then diarrhea, shock, and harm to the liver and kidneys, with bone marrow damage trailing later. Because signs can hold off for hours, rush to a vet on suspicion alone instead of waiting for symptoms to surface.
Dogs Severe
Dogs love to dig up and gnaw the corms, which pack the highest dose of all. Watch for drooling, bloody vomiting and diarrhea, collapse, and organ failure that can stay hidden until long after the meal. This poisoning often turns deadly, so treat the smallest nibble as a full emergency.
Horses Severe
A horse that grazes autumn crocus is hit with violent colic and bloody diarrhea, then shock and failing organs. Colchicine works the very same way at horse scale, and the outcome is often fatal. Phone the vet the instant you suspect a mouthful went down.
Rabbits Severe
Not one bite is safe for a rabbit. Colchicine in the leaves, flowers, and corms triggers severe gut damage and a fast crash, and a small body has next to no margin to spare. Bar this plant completely from any spot a rabbit might reach.
Livestock Severe
Cattle, sheep, and goats fall ill from autumn crocus both on pasture and in hay, where the toxin keeps its punch even after drying. Bloody scouring, weakness, and organ failure set in, and animals can die. A bitter taste turns some grazers away, yet hungry stock and tainted hay remain the true danger.
Birds Severe
Colchicine poisons birds just as surely as mammals, and a pecking hen or inquisitive parrot can swallow a fatal dose from a corm or seed. Look for crop and gut distress, weakness, and a quick downhill slide. Keep birds clear of the plant and any seed it scatters.
People Caution
No part of autumn crocus belongs on a plate, and people have died after taking the corms for wild garlic or the plant for true saffron. Swallowing any part can bring on severe vomiting, bloody diarrhea, multi-organ failure, and bone-marrow suppression, with no antidote to count on. Even handling it can sting the skin, 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 shows up far more than anything else, though one named pick does surface in gardens.
Pleniflorum
Its blooms come double and rose-pink, a clear step away from the single, star-shaped lilac-pink flowers the species puts out.
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 with ease once it has settled in, and the quickest routes all build on the corm rather than holding out for seed.
Offsets & pupsEasy
Lift in summer after leaves die back · Blooms the following fall once established
Every corm throws off little offsets clustered around its base. Dig the clump in summer after the leaves have died back, twist the offsets loose, and tuck them back in 3 to 6 inches deep and about 6 inches apart. They root in quickly and reward you with flowers 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 itself tight and flowers thin out, lift and split it. Tackle this in summer after the foliage dies back but before the flower stems rise, roughly every 3 years. Divided corms frequently bloom that same fall, or the season right after.
Bulbs & cormsEasy
Plant dormant corms in mid- to late summer (August) · Flowers the same fall after late-summer planting
Pop dormant corms into the ground in mid- to late summer, around August, and watch them flower that very fall. Get them planted the day they arrive, because these corms store poorly and lose their punch fast on the shelf.
SeedModerate
Sow outdoors when ripe · Slow; seed-grown plants take several years to reach flowering size
Seed takes the patient route. Sow it outdoors the moment it ripens, then settle in to wait, since seed-grown plants need several years to reach flowering size. Splitting corms or pulling offsets brings blooms much, much sooner.
Myths
Autumn crocus is just a fall-blooming spring crocus and is equally harmless.
They are two plants with no connection at all. Autumn crocus is Colchicum autumnale in the family Colchicaceae, whereas 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 the giveaway is its count of six stamens against 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. A faint resemblance is all the two ever shared.