Deadly fibrecap

Description

The deadly fibrecap is a medium-sized mushroom with a conical to convex cap (3–9 cm), silky and fibrous, without scales. When young it is white or cream, but it soon reddens: it becomes brick-red, and in the centre even vermilion. The gills are at first whitish, then olive-rust, and red when pressed. The cylindrical stem has no ring and turns pink when cut.

It grows from the end of May to October under deciduous trees, especially beeches, oaks and limes, in woods, parks and thickets, often on calcareous soils. In Poland it is common.

It is a deadly poisonous species, containing large amounts of muscarine. Mushroom pickers confuse it mainly with young St George's mushrooms and field mushrooms. A warning feature is the reddening of the cap, stem and pressed gills. All fibrecaps and fibrecap relatives are regarded as inedible. If you are not sure of the species, do not pick it and do not eat it.

Identification features

Cap

Diameter 3–9 cm (descriptions also give values up to 8 cm), conical-convex to hemispherical. Margin thin, inrolled in young specimens, straight and radially split in older ones. Surface dry, silky, without scales, covered with fine fibres. In young fruiting bodies white or pale cream, soon becoming brick-red, even vermilion, especially in the centre; edges paler. Colour variable, turns yellow or brown with age, and reddened patches and streaks also appear on the stem and gills; fades in the sun.

Hymenophore (underside of the cap)

Gills broad, thin, rather crowded, notched or free at the stem (descriptions also give narrowly adnate gills). At first whitish, then dark olive-rust; red when pressed. Edges uneven, frosted.

Stem

Height 5–20 cm, thickness 0.8–2 cm, cylindrical, solid, without a bulb at the base or at most with a small bulblet; no ring. Surface covered with whitish, pink or vermilion fibres, the top frosted.

Flesh

White in the cap (descriptions also give a colour at first yellowish, later dark pink), strongly pinkening in the stem. Smell pleasant, fruity; taste mild — it must never be tested; do not taste the flesh of this or any suspicious mushroom.

Spore print and spores

Spore print ochre-brown. Spores oval-bean-shaped, sometimes irregular, 9–12 (14.5) × 5–8 µm.

Habitat and distribution

Ecology. Mycorrhizal fungus. Grows on leaf litter and soil in woods, city parks and thickets, especially under deciduous trees — beeches, oaks, limes — but also under pine; most often in beech woods and on calcareous soils. In Israel described under the oak Quercus calliprinos and pines.

Distribution. Recorded only in Europe (and, according to some descriptions, in eastern Anatolia and Israel); more frequent in southern Europe. In Poland many localities have been described and it is regarded as common. Not legally protected.

Fruiting. From the end of May to the beginning of October (descriptions also give: spring and summer).

What can it be confused with?

• Calocybe gambosa (St George's mushroom) — Young fruiting bodies are the most similar. St George's mushroom does not turn red, older specimens have a different gill colour (pale, not olive-rust) and a mealy smell.
• Inocybe godeyi (Godey's fibrecap) — Stem with a distinct bulb.
• Inocybe rimosa (split fibrecap) — More brownish specimens of the deadly fibrecap may resemble it, but in the split fibrecap there is not even a trace of reddish colour on the cap.
• Agaricus campestris and other field mushrooms — Listed as confused species; mature field mushrooms have dark gills, but they have a ring and the fibrecap does not. Further differences — no data.
• Cortinarius caperatus (the gypsy) and Tricholoma terreum (grey knight) — Listed as confused species (including in Israel with knights); detailed differences — no data.

Never rely on a single feature. If you are not sure — do not pick it; show the mushroom to a qualified mushroom expert.

Interesting facts

• The species has two long-used scientific names: Inocybe erubescens (Blytt, 1904/1905) and I. patouillardii (Bresadola, 1905, in honour of Narcisse Patouillard); Blytt's name has priority.
• After the phylogenetic studies of 2019 the species was moved from the genus Inocybe to Inosperma, because it is only a distant relative of the other fibrecaps.
• One death after eating it has been recorded, in Surrey in 1937.
• It is also called the "brick-red tear mushroom" and włókniak ceglasty.