How to tell Cortinarius multiformis from Fool's webcap
How they differ, how to recognize them and which is more dangerous — a mushroom comparison
Warning: Fool's webcap(Cortinarius orellanus)
DEADLY POISONOUS
Eating it can cause death. Do not pick it and do not taste it.
It contains orellanine (Cortinarius orellanus contains the highest concentrations among webcaps), as well as the related compounds orelline and orellinine. Orellanine is a nephrotoxin that destroys the cells of the kidneys' proximal tubules through oxidative stress. It accumulates in the kidneys and produces symptoms slowly.
Its unique feature is a record delay of symptoms: in a review of 90 described poisonings (Danel et al., 2001), digestive upset usually appeared on the third day and signs of kidney damage on the eighth or ninth, occasionally even later. Because of this delay: people don't link their worsening condition to a mushroom eaten a week earlier, by then several portions may already have been eaten, medical help comes late — when the kidneys are already badly damaged, activated charcoal and gastric lavage are no longer effective.
Clinical phases:
Phase 1 (from day 2, most often days 3-7): thirst, dry mouth, headache, nausea, lower back (kidney) pain, mild gastroenteritis. The symptoms are often written off as a cold or food poisoning.
Phase 2 (days 7-14): oliguria (reduced urination), then anuria (no urine at all). Rising creatinine and urea in the blood, hyperkalemia. This is the phase of full-blown acute kidney failure.
Phase 3 (day 14+): either recovery of kidney function (partial, with scarring), or progression to chronic kidney failure requiring lifelong hemodialysis or a kidney transplant.
Deaths have been described (for instance in a mass poisoning in Poland), but the more common outcome is chronic kidney failure: in the review by Danel et al. (2001) it developed in about half of the cases.
Treatment: there is NO specific antidote. Symptomatic: hemodialysis to remove toxins and support the kidneys, infusion therapy, electrolyte correction, and in severe cases a kidney transplant. The effectiveness of treatment depends critically on early detection — the sooner doctors start monitoring the kidneys, the sooner they can begin supportive treatment and dialysis. There is no specific treatment proven to limit the damage.
Prevention: no orange-russet gilled mushroom with a cobwebby cortina goes into the basket. NO EXCEPTIONS. It has no culinary value, and there are no similar edible species on a dangerous scale (the chanterelle has ridges instead of gills, honey fungus has a ring and paler gills).
If you suspect poisoning, call an ambulance immediately: 112 (the European emergency number) or your local emergency number
The short answer
Cortinarius multiformis and Fool's webcap look alike, so they're easy to mix up — but Cortinarius multiformis is inedible, while Fool's webcap is deadly poisonous. The main visible difference: cap color: Cortinarius multiformis — yellow, orange, brown, Fool's webcap — orange, red, brown. The mushrooms also differ in the following features: cap surface, stem, partner trees. If you have even the slightest doubt, leave the mushroom be.
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Cortinarius multiformis
Cortinarius multiformis
Fool's webcap
Cortinarius orellanus
📊 Comparing characteristics
⚠ Highlighted rows are the key differences between the edible and the dangerous mushroom
| Characteristic | Cortinarius multiformis | Fool's webcap |
|---|---|---|
| ⚠ Edibility class | Cortinarius multiformis Inedible | Fool's webcap Deadly poisonous |
| Season | Cortinarius multiformis SummerAutumn | Fool's webcap SummerAutumn |
| Use | Cortinarius multiformis Not eaten | Fool's webcap Not eaten |
| Size | Cortinarius multiformis Medium (5–15 cm) | Fool's webcap Medium (5–15 cm) |
| ⚠ Cap color | Cortinarius multiformis YellowOrangeBrown | Fool's webcap OrangeRedBrown |
| Cap shape | Cortinarius multiformis Convex | Fool's webcap Convex |
| ⚠ Cap surface | Cortinarius multiformis Smooth | Fool's webcap Velvety |
| Taste | Cortinarius multiformis Unknown | Fool's webcap Unknown |
| Smell | Cortinarius multiformis Odorless | Fool's webcap Odorless |
| Flesh color change | Cortinarius multiformis No change | Fool's webcap No change |
| Hymenophore | Cortinarius multiformis Gilled | Fool's webcap Gilled |
| ⚠ Stem | Cortinarius multiformis Bulbous | Fool's webcap Central |
| Ring (veil) | Cortinarius multiformis Ring remnants | Fool's webcap Ring remnants |
| Volva | Cortinarius multiformis No volva | Fool's webcap No volva |
| Substrate | Cortinarius multiformis Soil | Fool's webcap Soil |
| Nutrition type | Cortinarius multiformis Mycorrhizal | Fool's webcap Mycorrhizal |
| ⚠ Partner trees | Cortinarius multiformis BeechOakHornbeamBirch | Fool's webcap OakBeechBirch |
📅 Seasonality
Cortinarius multiformis
Fruiting season
August – October
Fool's webcap
Fruiting season
August – October
🔬 Morphology
Cap
Cortinarius multiformis
The cap is 5-10 cm across, hemispherical with an inrolled margin in young mushrooms, becoming convex to flat with a low umbo over time. The color is orange-yellow, honey-ochre, reddish-yellow, darker when young, fading to pale ochre with age. The surface is smooth, slightly slimy in wet weather. Older mushrooms often show fine radial cracks.
Fool's webcap
Cap 3-8 cm across, hemispherical to conical-convex in young mushrooms, later becoming convex to flat with a low umbo. Color orange-red, fiery orange, russet-orange, darker in the center, paler at the margin. Surface velvety and dryish, microscopically scaly, not slimy. The cap margin is thin, with fine radial fibers in young mushrooms.
Hymenophore
Cortinarius multiformis
The hymenophore is gilled — the gills are attached to the stem and moderately crowded. In young mushrooms they are pale cream to pale ochre, later turning rusty brown as the spores ripen. The spore print is rusty brown. In young mushrooms the gills are covered by a cobwebby partial veil (the cortina).
Fool's webcap
Gills — attached to the stem, widely spaced, broad. In young mushrooms russet-orange, darkening over time to rusty brown as the spore powder ripens. Spore print rusty brown — a diagnostic feature of the genus Cortinarius. In young mushrooms the gills are covered by a cobweb-like partial veil (cortina).
Stem
Cortinarius multiformis
The stem is 5-9 cm tall, 1-2 cm thick, cylindrical, with a pronounced bulbous base (like an onion bulb). The color is whitish to pale ochre. On the stem you'll see remnants of the cobwebby cortina dusted with rusty-brown spores.
Fool's webcap
Stem 4-9 cm tall, 0.7-1.5 cm thick, cylindrical, long, relatively slender, often thickening toward the base. Color yellow-orange to yellow, paler toward the base. The surface has fine lengthwise fibers. Remnants of the cobwebby cortina on the stem form a thin band with rusty-brown spores that have settled on the veil remnant.
Flesh
Cortinarius multiformis
The flesh is firm, white to pale cream. When cut it does not change color or turns slightly yellow. The smell is faint and neutral.
Fool's webcap
Flesh firm, orange-yellow to brownish yellow. When cut, it does not change color. Smell faint, neutral; in some populations with a hint of radish. Taste mild, indistinct (do NOT taste it — even a small amount of toxin is dangerous).
Smell
Cortinarius multiformis
Faint, neutral, mushroomy, with no distinctive notes.
Fool's webcap
Faint and neutral, with no distinctive notes. The smell is NOT a warning sign — the mushroom smells neutral, which makes it even more treacherous.
📍 Habitats
Cortinarius multiformis
Fool's webcap
👀 Similar mushrooms — don't mix them up!
❓ Frequently asked questions
Can Cortinarius multiformis and Fool's webcap be mixed up?
How to tell Cortinarius multiformis from Fool's webcap?
Which is more dangerous — Cortinarius multiformis or Fool's webcap?
Is Fool's webcap edible?
When do Cortinarius multiformis and Fool's webcap grow?
Sources
- [1]Вікіпедія (українська)
- [2]Атлас грибів України, Зеров Д.К. (1979)
- [3]MycoBank Database
- [4]Index Fungorum
- [5]GBIF
- [6]iNaturalist Ukraine