Brown roll-rim

Description

The brown roll rim is a brown, slightly funnel-shaped mushroom with a cap up to about 13 cm across and a distinctly inrolled margin. The cap is olive-brown to rusty, slimy in wet weather. The gills are yellowish to rusty, crowded and running down a short stem, and they turn brown when touched and damaged. The flesh also turns brown when cut.

It grows from summer to autumn in almost every type of forest, under birches, oaks, alders, pines and spruces, usually in groups, also on lawns. In Europe it is common.

Today it is regarded as poisonous: in some people it causes a dangerous immune reaction, even if they ate it for years without symptoms. Do not collect it for eating.

Identification features

Cap

Diameter up to 12–13 cm (descriptions also give usually 4–12 cm, no more than 15 cm); when young gently arched with a distinctly inrolled margin, later flat or funnel-shaped and concave, the margin still inrolled. Colour yellow-brown, olive, ochre-brown or reddish-brown. Finely felty when young, later bald; dark brown spotted when damaged; in dry weather dry and shiny, in wet weather very slimy.

Hymenophore (underside of the cap)

Gills thin, crowded, distinctly decurrent onto the stem, forked, yellowish or rusty, turning brown when damaged; in young specimens wrinkled, irregular and anastomosing near the stem, and may resemble pores. They separate easily from the flesh, like the tubes of boletes.

Stem

Height 3–7 cm, thickness 1–2 cm (descriptions also give up to 3 cm), cylindrical, thick, solid, smooth, often narrowing downwards, may be crooked; colour similar to the cap, usually paler; turns brown when damaged. No ring.

Flesh

Yellow, yellowish-white or pale ochre, at first firm, later soft, turning reddish-brown or rusty-brown when cut. Taste slightly sour, smell faint. Do not taste this mushroom.

Spore print and spores

Spore print ochre-brown to brown. Spores ellipsoid, smooth; dimensions are given inconsistently: 8–18 × 4.5–6 µm and 7.5–9 × 5–6 µm.

Habitat and distribution

Ecology. Ectomycorrhizal fungus with a wide range of host trees: birch, oak, alder, pine, spruce and others. More frequent in coniferous forests, prefers damp places and avoids calcareous soils; also grows on lawns and old meadows. Protects trees from heavy metals and some pathogens (laboratory studies). Sometimes parasitised by Hypomyces chrysospermus.

Distribution. The whole northern hemisphere in the temperate zone; common in Europe. Introduced to Australia, New Zealand, southern Africa and South America. Usually grows in groups. Not legally protected in Poland.

Fruiting. From summer to autumn (descriptions also give: late summer and autumn).

What can it be confused with?

• Paxillus filamentosus (alder roll-rim) — Scaly cap, grows only under alders; the pale yellow flesh browns only slightly and the deep yellow-ochre gills do not change colour when damaged.
• Paxillus obscurosporus — Larger fruiting bodies (cap up to 40 cm), margin flattening with age, stem with a cream-coloured layer of mycelium at the base.
• Paxillus validus — Cap up to 20 cm, stem of roughly even thickness; reliably distinguished by the crystals in the rhizomorphs.
• Lactarius spp. (milk caps), e.g. Lactarius turpis — Milk caps exude milk; the roll-rim has no milky sap. L. turpis is darker, olive.
• Tapinella atrotomentosa, Tapinella panuoides, Phylloporus arenicola — Listed as similar; 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 German mycologist Julius Schäffer died in 1944 after a meal of brown roll rim: after an hour he had vomiting, diarrhoea and fever, and after 17 days he died of kidney failure.
• Despite its gills it belongs to the Boletales, so it is more closely related to boletes than to typical gilled mushrooms.