Crocus or autumn crocus (Colchicum)? The difference in 3 criteria

Daniel Platteau Flower bulbs

The trio of misunderstanding

Picture a damp meadow on a September morning. The grass is still green and short, and suddenly, rising from the ground as if by magic, without a single leaf to accompany them, dozens of pink or mauve goblets stand ten centimetres above the soil. They are called "colchicums", "meadow saffron", "naked ladies" — and, confusingly, "autumn crocus" in English. The walker bends down and thinks: "Oh, crocuses." Wrong. Six months later, in March, the same walker finds almost identical mauve goblets in the same meadow, this time accompanied by thin, ribbon-like leaves: these are the real crocuses. And in between, in October, in a Mediterranean garden, they may come across a third flower, golden yellow this time, presented to them as an "autumn crocus" even though it is not a crocus at all.

This confusion is not trivial: it kills. Every year in Europe, people are hospitalised — and some die — after mistaking colchicum for wild garlic in spring, or believing they were harvesting saffron in autumn. Colchicine, the colchicum's alkaloid, has no antidote.

And yet these three plants are also three excellent ornamentals, easy and generous, flowering when nothing else does. This article has two aims: to tell you who is who, and to give you practical criteria so you never get it wrong again — in the garden or on your plate.

Three families, three separate stories

The first habit to acquire: these three plants do not belong to the same botanical family. Their resemblance is a textbook case of convergent evolution — a goblet-shaped flower carried on a floral tube emerging straight from the ground is simply an efficient way to flower quickly and low down, while protecting the reproductive organs from the cold.

The crocus (Crocus spp.) belongs to the Iridaceae, the family of irises and gladioli. The genus has about 250 recognised species, ranging from western Europe to western China, with a spectacular centre of diversity in the Balkans, Turkey and the Near East. Some species flower in spring (Crocus vernus, Crocus tommasinianus, Crocus chrysanthus), others in autumn (Crocus sativus, saffron; Crocus speciosus; Crocus nudiflorus). That is already a trap: true autumn-flowering crocuses do exist, and the most famous of them is precisely the one people confuse with colchicum.

The colchicum (Colchicum spp.) belongs to the Colchicaceae, a separate family, long attached to the Liliaceae before modern phylogenetic revisions. The genus has around a hundred species. Its name comes from Colchis, a region of the Caucasus and the mythological homeland of the sorceress Medea — which says a lot about its reputation as a poison plant since antiquity. Meadow saffron (Colchicum autumnale) is the emblematic European species of damp meadows.

Sternbergia (Sternbergia lutea) belongs to the Amaryllidaceae, the family of daffodils, amaryllis and… garlic and onions. It is our "odd one out", and its botanical lineage explains a lot, especially its chemistry, which is very different from that of colchicum. The genus, named after the Czech botanist Kaspar Maria von Sternberg (1761–1838), has fewer than ten species, ranging from the Mediterranean basin to Iran and Kashmir.

The first criterion that never fails: count the stamens

If you remember only one thing from this article, let it be this.

Crocus: 3 stamens.
Colchicum: 6 stamens.
Sternbergia: 6 stamens.

This criterion is absolute, with no exceptions, and rests on the fundamental structure of the families involved. Iridaceae have three stamens; Colchicaceae and Amaryllidaceae have six.

In practice: pick the flower (or crouch down to look inside), and count the little filaments ending in a pollen sac. Three? It's a crocus. Six? It is not a crocus, so it is not saffron, so you eat nothing.

A second confirming criterion, just as clear-cut: the style, the extension of the ovary that receives the pollen.

In the crocus, the style is single and divides into three usually very colourful stigmas — which, in Crocus sativus, is exactly what saffron is: three bright red-orange threads.
In colchicum, there are three separate, free styles, long and thin, separate right down to the base.

Saffron is therefore a set of three red threads per flower, coming from a single point. If you see three styles separate from the bottom of the flower, and six stamens, you are looking at a colchicum: the "saffron harvest" you were about to gather would land you in A&E.

A third criterion, useful but less reliable on its own: the colour of the stamens. In the saffron crocus, the anthers are yellow and the stigma bright red. In colchicum, the anthers are yellow but the styles are pale, whitish or pinkish. In Sternbergia lutea, everything is yellow: petals, stamens, the whole flower.

The calendar: the gardener's key

The famous saying — crocuses in spring, colchicums in autumn — is partly wrong, and therein lies the trap. Let's go through it properly, with the real flowering periods.

February to April: spring crocuses. Crocus tommasinianus (the earliest, often from February, pale mauve), Crocus chrysanthus and its cultivars (yellow, cream, two-tone), Crocus vernus and its large-flowered Dutch hybrids (the classic "Dutch crocuses"). At this time of year, no colchicum is in flower: colchicum produces its leaves in spring — broad, glossy, in a clump, with no flowers at all. Remember this point well: it is at the heart of the food danger.

September to October: the great mix-up. This is when the following all flower at the same time:

meadow saffron (Colchicum autumnale), lilac-pink, with no leaves;
ornamental autumn crocuses (Crocus speciosus, mauve with blue veins; Crocus nudiflorus, Crocus banaticus);
saffron (Crocus sativus), violet with red stigmas, harvested from October to early November;
sternbergia (Sternbergia lutea), golden yellow, usually from late September to November, often with its leaves or just before they appear.

This autumn traffic jam explains almost all accidents.

A field tip, useful but never to be used alone: colchicum flowers completely bare, without a single leaf, hence its nickname "naked ladies". The autumn crocus usually puts out, with or shortly after its flowers, its thin linear leaves marked with a white central stripe. Sternbergia shows relatively broad, ribbon-like dark green leaves, often present during flowering.

The real danger: colchicine

It must be said plainly: all parts of the colchicum are poisonous — bulb (in fact a corm), leaves, flowers and above all seeds. The substance responsible is colchicine, an alkaloid that blocks tubulin polymerisation and therefore cell division (mitosis). It attacks first the tissues that renew rapidly: intestine, bone marrow, hair follicles.

The figures are chilling. The toxic dose is estimated at around 0.1 mg/kg, the potentially lethal dose at around 0.8 mg/kg, and the outcome is almost always fatal above 0.8 to 1 mg/kg according to clinical toxicology data. For a 70 kg adult, a few leaves are enough. The seeds are particularly concentrated.

The clinical picture is deceptive, which is what makes it so dangerous: after a delay of 2 to 12 hours — during which the victim feels perfectly well and thinks they have escaped the worst — come nausea, vomiting, profuse diarrhoea and abdominal pain, suggesting ordinary gastroenteritis. Then, from 24–72 hours, the serious phase sets in: multi-organ failure, liver and kidney damage, heart rhythm disorders, a collapse in white blood cells and platelets (bone marrow aplasia). Massive hair loss may occur around day 10 in survivors.

No specific antidote is available. Anti-colchicine antibody fragments were used experimentally in France in the 1990s, but they have never been marketed. Treatment is purely symptomatic and intensive: early gut decontamination, activated charcoal, intensive care. Haemodialysis is ineffective, because colchicine has a very large volume of distribution.

The two poisoning scenarios you absolutely must know

Scenario 1, the most common: the spring mix-up with wild garlic. In spring, colchicum produces a rosette of broad, oblong, glossy, bright green leaves, which often grow in the same damp meadows and woodland edges as Allium ursinum. European poison centres regularly report cases, several of them fatal. How to tell them apart:

Smell: crush the leaf. Wild garlic gives off a strong, immediate garlic smell. Colchicum has no smell. Beware, though: after handling wild garlic, your fingers smell of garlic and skew the test — hence the absolute safety rule, pick leaf by leaf and smell each leaf with clean hands.
Leaf stalk: wild garlic has a clearly stalked leaf, with a long stalk distinct from the blade, and the leaves come out of the ground singly. Colchicum leaves are stalkless, sheathing, and come out grouped in a clump from a single point.
Underside: matt in wild garlic, glossy on both sides in colchicum.
Veins: wild garlic has a marked midrib and visible secondary veins; colchicum has very regular parallel veins, typical of a monocot.

Lily of the valley (Convallaria majalis, also poisonous) and arum are the other two classic lookalikes of wild garlic.

Scenario 2: the false saffron harvest. In autumn, a colchicum is taken for Crocus sativus. The stamen test (3 vs 6) and the style test (1 bright red three-branched style vs 3 free, pale styles) is conclusive here. Remember too that genuine saffron consists only of the red stigmas, never the petals.

A paradoxical and fascinating point: colchicine is also an essential medicine, known since antiquity — Dioscorides already described colchicum as a poison, and the Byzantine physician Alexander of Tralles used it against gout in the 6th century — and used today to treat acute gout, familial Mediterranean fever and pericarditis. Since 2019 and the COLCOT trial, it has even been studied in cardiology for preventing cardiovascular events after a heart attack, thanks to its anti-inflammatory effect. But its therapeutic margin is among the narrowest in the whole pharmacopoeia: medication overdoses, including through interactions with certain antibiotics (macrolides) or antifungals, are themselves a cause of serious poisoning. Colchicine is also a major laboratory tool in plant genetics, used to induce polyploidy in crop plants.

And is sternbergia dangerous?

Less publicised, but it is not edible either. As a member of the Amaryllidaceae, Sternbergia lutea contains alkaloids typical of its family — lycorine, galanthamine, tazettine and related compounds — concentrated in the bulb. Eating it mainly causes digestive upset: nausea, vomiting, diarrhoea, salivation. It is the same profile as the daffodil, whose bulbs are regularly mistaken for onions or shallots by careless cooks. Nothing comparable to the lethality of colchicine, but no reason to taste it.

An interesting point for research: galanthamine, isolated from Amaryllidaceae (notably the snowdrop, Galanthus), is now an approved medicine for Alzheimer's disease, as an acetylcholinesterase inhibitor. The genus Sternbergia is regularly the subject of phytochemical studies for its alkaloid profile and neuroprotective potential.

Finally, a conservation note: Sternbergia lutea is a protected species in France, where it is native only in a few Mediterranean sites (Var, Alpes-Maritimes, Corsica in particular), and its wild status there is debated — many populations are probably of garden origin, naturalised long ago. Never take bulbs from the wild: buy them from a grower.

Growing them in the garden: a how-to

The good news: these three plants are among the easiest in the garden, and together they cover a flowering season from September to April.

Crocuses

Planting: spring crocuses are planted from September to November; autumn crocuses, including saffron, from July–August (ordering them too late is a classic mistake). Depth: 5 to 8 cm, about three times the height of the corm. Spacing: 5 to 10 cm. Free-draining soil is essential, full sun preferably.

Naturalising: Crocus tommasinianus is the champion at colonising a lawn — it self-seeds and forms carpets within a few years. Golden rule: don't mow until the foliage has completely yellowed, usually at the end of May. This is when the corm rebuilds its reserves.

The case of saffron: Crocus sativus is a sterile triploid, unable to produce seed, entirely dependent on humans propagating its corms for several thousand years. It needs very free-draining soil, a hot, dry summer (its rest period), and lifting and dividing every 3 to 5 years. Allow about 150 flowers for 1 gram of dried saffron.

Pests: field mice and voles love crocus corms; so do squirrels. Planting in a wire basket or mulching with gravel can help. Sparrows sometimes shred the yellow flowers.

Colchicums

Planting: from July to early September, 8–10 cm deep, in moist soil that is not too dry in summer, in partial shade or light sun. They cope with competition from grass.

Watch the foliage: and here we must be honest with the amateur gardener — in spring, colchicum produces broad, tall leaves (up to 30–40 cm) that last until June and yellow rather untidily. Don't cut them, but plan ahead: plant colchicums among perennials that will hide them (hardy geraniums, hostas, lady's mantle), rather than along a path.

Safety: do not plant colchicums in a garden used by young children, or label them clearly. Animal poisonings (dogs, horses, cattle) are documented — hay contaminated with colchicum stays toxic after drying, as colchicine is heat-stable. It is a real issue in livestock farming: colchicum keeps its toxicity in hay and silage.

Recommended varieties: Colchicum speciosum 'Album' (pure white, superb), Colchicum 'Waterlily' (double, bright pink, spectacular but heavy — it tends to flop), Colchicum byzantinum (very free-flowering).

Sternbergia

Planting: in August–September, 10–15 cm deep — deeper than crocuses. Very free-draining soil, preferably chalky, in the hottest spot possible: the foot of a south-facing wall, a rock garden, a low wall.

The secret of success: sternbergia has a reputation for being temperamental, but it is almost always for the same reason — it needs a hot, dry summer rest. Too much summer watering or a heavy, damp soil, and it will not flower. It also hates being disturbed: leave it alone for years and it will form increasingly free-flowering clumps. It is hardy to about −10/−12 °C, which limits it in cold climates, but it does very well in a pot of sandy compost kept out of the winter rain.

Foliage: dark green, ribbon-like, appearing with or just after the flowers and lasting until spring. It is an ideal autumn-flowering plant for dry and Mediterranean gardens, alongside ivy-leaved cyclamen and nerines.

The field checklist to memorise

Before any foraging, whatever the season:

Count the stamens. Three = crocus. Six = colchicum or an amaryllid. Six = don't eat.
Look at the styles. One bright red three-branched style = saffron. Three free, pale styles = colchicum.
In spring, for wild garlic: clean hands, leaf by leaf, garlic smell required, distinct leaf stalk, leaves single and not in a clump.
If in doubt, don't eat it. No exceptions. No "roughly right" criteria.
If ingestion is suspected, even without symptoms: call a poison centre immediately (in Belgium: 070 245 245; elsewhere, your local poison control centre) or the emergency services (112). Do not wait for digestive symptoms: the useful window for decontamination is measured in hours, and the symptom-free phase is deceptive. Keep a sample of the plant for identification.

These three genera deserve a place in the garden — they light up seasons when everything else is asleep. You just need to know them by name, and to count to six.