Bulb · Colchicaceae
Autumn Crocus
Colchicum autumnale
Bare lilac-pink blooms appear out of nowhere 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 has a way of surprising the whole garden. Its lilac-pink, goblet-shaped flowers lift straight out of bare soil in late summer and fall, not a leaf in view, which is how it earned the name naked ladies. Come the following spring, the broad strappy foliage arrives to feed the corm, then retires by summer ahead of the next show of bloom.
The name misleads, because it shares no kinship with the spring crocus you may already grow. It sits in the family Colchicaceae and rises from a corm rather than a true bulb, settling in beautifully along a woodland edge or drifting through a lawn in zones 4 to 9. Plant it once and it widens into broader clumps with each passing season.
Here is the part that demands respect. Every part of the plant carries colchicine, among the deadliest compounds you will ever keep in a garden, and nothing reverses it once eaten. The flower is lovely and the plant easy to keep, but it draws a firm boundary between the border and anyone or anything that might take a bite.
Care
The short version: set the corms where they get full sun to light shade in well-drained soil, water moderately only while the spring leaves are present, and let those leaves turn yellow on their own before you clear them away.
Light
Give autumn crocus full sun for the most generous flowering, though it accepts partial shade with little fuss. A woodland edge suits it nicely, offering open light in spring while the leaves are at work and dappled shade as the year wears on.
Water
Keep the soil at medium moisture while the foliage stands in spring, then ease off almost entirely as the corms slip into summer dormancy. Sharp drainage is non-negotiable, since waterlogged ground rots the corm quicker than anything else.
Soil
It will settle into loam, clay, or sand as long as the ground is organically rich and well drained. A pH from 6.0 to 7.5 suits it, and the single thing that counts most is that water never lingers around the corm.
Temperature
This is a thoroughly cold-hardy plant, at ease across zones 4 to 9 and tolerant from roughly -4°F to 75°F (-20°C to 24°C). It depends on winter chill to perform and brushes off hard frost with no protection at all.
Humidity
Everyday outdoor humidity is all it asks, so there is nothing to track or adjust. What matters far more is keeping the spring leaves dry and well spaced, because damp, crowded foliage invites smut.
Feeding
Work a balanced bulb fertilizer or compost into the soil at planting in fall and that is essentially the whole job. The corm builds its own reserves from the spring leaves, so heavy feeding does little for it.
Pruning
There is no real pruning to take on. Allow the spring foliage to die back on its own so the corm can lay in supplies for the next bloom, and gather the leaves only once they have turned yellow. Never trim the leaves while they remain green.
Repotting
In the ground it calls for dividing rather than repotting, every 3 years or so as the clumps grow crowded. Watch for fewer or smaller flowers, tightly packed clumps, and corms working their way up to the surface.
Size & spacing
The plants keep low, standing about 6 to 10 inches (15 to 25 cm) tall with a matching spread. Place the corms 6 inches (15 cm) apart and 3 to 6 inches deep so each has the room to clump up over the years.
When to plant
Autumn crocus keeps its own unusual calendar. Set the dormant corms out in late summer, around August, and the flowers arrive within weeks that same fall. The leaves bide their time until the following spring, feed the corm, and bow out by midsummer before 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 hardy and undemanding, so nearly every issue traces back to wet soil, hungry slugs, or the leaning habit of its bare stems. Match what you notice to the list below and step in early. Sharp drainage settles the one problem that can genuinely end the plant.
Mushy corms that never break the surface
Corm rot takes hold once the ground stays soaked and slow to drain. Dig one up and the flesh comes away soft, off-colored, and foul instead of staying firm. Bin anything spoiled and move the sound corms into sharply drained ground or a raised bed, since dry footing is your only line of defense here.
Fix:
- Discard rotted corms
- Replant healthy corms in sharply drained soil or a raised bed
Gnawed corms and ragged openings in fresh shoots
What you are seeing is slug and snail damage, the kind that turns up most in cool, shaded corners of the bed. Check for slime trails and soft, hollowed patches on corms sitting near the surface, then collect the offenders by hand after dusk or lay out bait. Open up the drainage and pull mulch back from the corms so there is less cover for them to shelter under.
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 across the spring foliage
Those raised blisters that split open into dark, powdery dust are fungal smut working through the leaves. Lift out any affected foliage and dispose of it the moment it appears. The trouble settles in where leaves stay wet and packed together, so give the corms breathing room and keep water off the foliage.
Fix:
- Remove and destroy infected leaves
- Avoid overhead watering and crowding to improve air flow
Bare flower stems tipping and sprawling
This is the plant being itself, not a fault you need to fix. The blooms arrive on naked, leafless stems through fall, with no foliage standing by to steady them, so they lean and go over in wind or rain. Settle them into a low groundcover or among short perennials, and the company around them holds the flowers up.
Fix:
- Underplant with a low groundcover to support stems
- Site among low perennials that hold flowers upright
Toxicity
Regard this plant as a poison, never a nibble. Every part holds colchicine, with the corms and seeds holding the most, enough that even a little can prove fatal to pets, livestock, and people, often with no warning for hours. There is no antidote, so real safety comes down to 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 a cat takes from this plant puts it in genuine peril. Heavy drooling and bloody vomiting arrive first, with diarrhea, shock, and harm to the liver and kidneys close behind, and the bone marrow struck later still. Because the signs can hold off for hours, head to a vet on suspicion rather than waiting for them to surface.
Dogs Severe
Dogs unearth and chew the corms, which hold the highest concentration of all. Look for drooling, bloody vomiting and diarrhea, collapse, and organ failure that can stay hidden long after the meal. Cases like this are often fatal, so treat the smallest nibble as an emergency.
Horses Severe
A horse grazing on autumn crocus is hit with violent colic and bloody diarrhea, then shock and failing organs. The colchicine acts the same way at a horse's scale, and the result is often deadly. Reach for the vet the instant a mouthful is suspected.
Rabbits Severe
For a rabbit there is no harmless taste of this plant. Colchicine in the leaves, flowers, and corms triggers severe damage to the gut and a swift decline, and a small body has next to no buffer. Keep the plant fully clear of anywhere a rabbit might roam.
Livestock Severe
Cattle, sheep, and goats fall ill from autumn crocus both in pasture and in hay, where the toxin holds its strength even once the plant has dried. Bloody scouring, weakness, and organ failure follow, and animals can die. A bitter taste turns some grazers away, but hungry stock and contaminated hay carry the real danger.
Birds Severe
Colchicine is as poisonous to birds as it is to mammals, and a pecking hen or inquisitive parrot can take a deadly dose from a corm or seed. Look for crop and gut upset, weakness, and a rapid downturn. Keep birds clear of the plant and any seed it drops.
People Caution
No part of autumn crocus belongs on a plate, and people have died 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. Even handling it can irritate the 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 is by some distance the form you will meet most often, though a single named selection makes its way into gardens.
Pleniflorum
This one wears double, rose-pink flowers in place of the single, star-shaped lilac-pink blooms the species shows.
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 it has settled in, and the quickest routes all work through the corm rather than holding out for seed.
Offsets & pupsEasy
Lift in summer after leaves die back · Blooms the following fall once established
Around its base, each corm throws off smaller offsets. Lift the clump through summer once the leaves have faded, ease the offsets away, and reset them 3 to 6 inches deep and about 6 inches apart. They take hold quickly and flower the following 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 packed and flowers thin out, dig it up and pull it apart. The window is summer, after the foliage fades but before the flower stems rise, roughly every 3 years. Divided corms will often bloom that very fall, or in the one to follow.
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 bloom that same fall. Get them in the ground as soon as they arrive, because these corms keep poorly in storage and lose vigor in short order.
SeedModerate
Sow outdoors when ripe · Slow; seed-grown plants take several years to reach flowering size
Seed asks for patience. Sow it outdoors the moment it ripens and then wait, since seed-grown plants need several years before they reach flowering size. Splitting corms or lifting offsets brings blooms a good deal sooner.
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 is loaded with colchicine in every part and is far more dangerous, and the giveaway is its six stamens against the three a true crocus carries.
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 completely separate Crocus sativus. A passing likeness is all the two have in common.