Bulb · Colchicaceae
Autumn Crocus
Colchicum autumnale
Bare lilac-pink blooms surface 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 reverses the usual order of things. Goblet-shaped, lilac-pink flowers push up directly from open soil in late summer and fall with no leaves alongside them, the habit that earns the name naked ladies. The broad, strappy foliage waits until the following spring, builds the corm's reserves, and dies back by summer ahead of the next flush of bloom.
The name misleads, because this is no kin to the familiar spring crocus. It sits in the family Colchicaceae and grows from a corm rather than a true bulb, settling readily into a woodland edge or drifting across a lawn through zones 4 to 9. Establish it once and it widens its clumps on its own from one year to the next.
The trade-off is grave. Colchicine runs through every part of this plant, ranking among the most lethal compounds found in any garden, and ingestion has no antidote. The flower is lovely and the growing is undemanding, yet it demands a firm boundary between the bed and anything inclined to take a bite.
Care
The short version: site the corms in full sun to light shade in well-drained soil, supply medium water only while the spring leaves are working, and allow that foliage to yellow on its own before you clear it away.
Light
Full sun drives the heaviest flowering, though autumn crocus accepts partial shade with little complaint. A woodland edge suits it, since the spot offers open light in spring when the leaves are feeding the corm and dappled shade through the later part of the year.
Water
Supply medium moisture while the foliage stands in spring, then withhold water almost completely as the corms enter summer dormancy. Sharp drainage is non-negotiable, because saturated ground rots the corm faster than any other cause.
Soil
Loam, clay, or sand all serve, provided the soil is organically rich and well drained. A pH from 6.0 to 7.5 suits it, and the priority above all else is that water never lingers around the corm.
Temperature
A genuinely cold-hardy plant, at home across zones 4 to 9 and tolerant from roughly -4°F to 75°F (-20°C to 24°C). Winter chill is a requirement for good performance, and hard frost passes without any protection.
Humidity
Everyday outdoor humidity is the whole of its demand, with nothing to monitor or adjust. What counts far more is keeping the spring leaves dry and well spaced, since damp, crowded foliage opens the door to smut.
Feeding
Mix a balanced bulb fertilizer or compost into the soil at planting in fall, and that covers it. The corm builds its own reserves from the spring leaves, so heavy feeding adds little.
Pruning
There is effectively no pruning. Allow the spring foliage to die back of its own accord so the corm can recharge for the next bloom, and remove the leaves only once they have yellowed. Never cut the leaves while they remain green.
Repotting
Grown in the ground, it calls for division rather than repotting, every 3 years or so as the clumps congest. Watch for fewer or smaller flowers, packed clumps, and corms working their way up to the surface.
Size & spacing
These plants stay compact, reaching about 6 to 10 inches (15 to 25 cm) tall with a comparable spread. Space the corms 6 inches (15 cm) apart and set them 3 to 6 inches deep so each has the room to build a clump over time.
When to plant
Autumn crocus keeps an unusual schedule. Set dormant corms out in late summer, around August, and the flowers arrive within weeks of that same fall. Leaves stay underground until the following spring, recharge the corm, and fade by midsummer ahead of the next round of 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 durable and low-maintenance, so nearly every problem traces back to wet soil, foraging slugs, or the flop of its bare stems. Match the symptom below and respond promptly. Sharp drainage forestalls the single issue capable of killing the plant.
Mushy corms that refuse to break dormancy
Corm rot takes hold once soil stays saturated and waterlogged. Dig one up and the flesh comes away soft, discolored, and foul instead of firm. Discard every rotted corm and move the sound ones into sharply drained ground or a raised bed, since keeping the corm dry is the only defense that works.
Fix:
- Discard rotted corms
- Replant healthy corms in sharply drained soil or a raised bed
Gouged corms and ragged holes punched through fresh shoots
The signature of slugs and snails, which concentrate where ground stays damp and shaded. Confirm it by the slime trails and the soft, scooped-out wounds on corms sitting near the surface, then collect the offenders by hand after dark or lay bait. Sharper drainage and pulling mulch back off the corms removes the moist cover these pests rely on.
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 bursting blisters across the spring foliage
Raised blisters that split open to release dark, powdery spores point to fungal smut in the leaves. Remove and burn affected foliage the moment it appears. The pathogen establishes wherever leaves sit wet and packed together, so give the corms room and keep irrigation off the leaf surface.
Fix:
- Remove and destroy infected leaves
- Avoid overhead watering and crowding to improve air flow
Naked flower stems tipping and sprawling sideways
Built into the plant rather than a fault to fix. The flowers open on bare, leafless stems in fall, and with no foliage standing alongside to brace them, wind and rain knock them flat. Setting the corms within a low groundcover or a stand of short perennials lets the neighboring growth hold the blooms upright.
Fix:
- Underplant with a low groundcover to support stems
- Site among low perennials that hold flowers upright
Toxicity
Regard this plant as a poison rather than anything edible. Colchicine saturates every part, concentrated most in the corms and seeds, to the point that a small amount can kill pets, livestock, and people, frequently with no warning for hours. With no antidote in existence, the only genuine safeguard is keeping it out of reach and washing your hands once you have handled it.
Toxic to
Cats · Dogs · Horses · Rabbits · Livestock · Birds · People
Cats Severe
Any bite of this plant puts a cat in genuine peril. Profuse drooling and bloody vomiting lead the way, with diarrhea, shock, and liver and kidney injury close behind, and bone marrow damage emerging later. Because the signs can trail the exposure by hours, head to a vet on suspicion rather than waiting for them to surface.
Dogs Severe
Dogs unearth and gnaw the corms, the part where the toxin runs strongest of all. Look for drooling, bloody vomiting and diarrhea, collapse, and organ failure that can hold off until long after the meal. Such poisoning is frequently fatal, so treat even a single nibble as an emergency.
Horses Severe
A horse grazing on autumn crocus develops violent colic and bloody diarrhea, then slides into shock and organ failure. The same colchicine acts identically at equine scale, and the result is often deadly. Phone the vet the instant a mouthful seems possible.
Rabbits Severe
No portion is safe for a rabbit to sample. Colchicine in the leaves, flowers, and corms triggers severe gut damage and a swift collapse, and a small body has almost no margin to spare. Keep the plant entirely clear of any area a rabbit can enter.
Livestock Severe
Cattle, sheep, and goats fall ill from autumn crocus both on pasture and in hay, where the toxin holds its potency even after drying. Bloody scouring, weakness, and organ failure set in, and deaths occur. A bitter taste turns some animals away, but hungry stock and contaminated hay carry the real hazard.
Birds Severe
Colchicine poisons birds as surely as it does mammals, and a pecking hen or inquisitive parrot can swallow a lethal dose from a corm or seed. Crop and gut distress, weakness, and a rapid decline follow. Keep birds away from the plant and from any seed it sheds.
People Caution
No part of autumn crocus belongs in food, and deaths have come from mistaking the corms for wild garlic or the plant for true saffron. Swallowing any portion can bring on severe vomiting, bloody diarrhea, multi-organ failure, and bone-marrow suppression, with no antidote available. Handling alone can irritate skin, so wear 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 dominates by a wide margin, though a single named selection appears in cultivation.
Pleniflorum
Its flowers are double and rose-pink, a clear departure from the single, star-shaped lilac-pink blooms the species produces.
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 increases readily once established, and every quickest method works through the corm rather than waiting on seed.
Offsets & pupsEasy
Lift in summer after leaves die back · Blooms the following fall once established
Every corm produces smaller offsets ringing its base. Dig the clump in summer after the foliage has died back, break the offsets loose, and reset them 3 to 6 inches deep and about 6 inches apart. They root in quickly and flower 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 grows congested and blooms thin out, lift and split it. Carry this out in summer after the foliage dies back yet before the flower stems rise, on roughly an every 3 years cycle. Divided corms frequently flower that same fall, or in the season after.
Bulbs & cormsEasy
Plant dormant corms in mid- to late summer (August) · Flowers the same fall after late-summer planting
Plant dormant corms in mid- to late summer, around August, and they flower that same fall. Get them in the ground as soon as they arrive, because these corms store poorly and shed vigor quickly out of soil.
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 wait, since plants raised from seed need several years to reach flowering size. Splitting corms or harvesting offsets brings blooms much faster.
Myths
Autumn crocus is just a fall-blooming spring crocus and is equally harmless.
The two are wholly separate plants. Autumn crocus is Colchicum autumnale in the family Colchicaceae, whereas the true spring crocus sits in the genus Crocus within the family Iridaceae. Colchicum carries colchicine throughout every part and is by far the more dangerous of the two, and a reliable tell is its six stamens against the three of a true crocus.
Autumn crocus can be used like saffron in cooking.
Keep every part of this plant away from food entirely. Eating Colchicum autumnale can be lethal because of its colchicine, while culinary saffron is harvested from the entirely separate Crocus sativus. A faint resemblance is all the two have in common.