Wrinkled Peach

Description

The wrinkled peach (Rhodotus palmatus) is a small mushroom with a bright pinkish-salmon, gelatinous and rubbery cap 2–6 cm across, covered with a characteristic network of paler veins and furrows that resembles the wrinkled skin of a peach. Underneath are crowded, pale pink gills, and the stem is short, usually set off-centre from the cap and covered with a delicate white down. The flesh is bitter.

It grows on dead wood of broadleaved trees, most often elms, in damp, shaded forests, from August to November. In Poland it is very rare and strictly protected, so finding it is an event; it must not be picked or its site destroyed.

It can be told apart from other pink wood-dwelling mushrooms by the distinct network on the cap, the notched or adnexed gills and the bitter taste of the flesh. It is not suitable for eating.

Identification features

Cap

Diameter 1.5–9 cm (usually 2–6 cm); convex when young, flattening or becoming semicircular with age, with an inrolled margin. Cap surface gelatinous, bright pinkish-salmon to orange or reddish, covered with a conspicuous network of paler veins and ridges surrounding deep, narrow furrows or pits. The colour, size and shape of the fruiting bodies depend on the lighting conditions during development. Flesh firm but rubbery.

Hymenophore (underside of the cap)

Gills adnexed to notched (adnate according to some descriptions), crowded, thick, up to 11 mm wide, unforked, pale reddish to pinkish, paler than the cap, not changing colour; edges even. Lamellulae form 2–4 length levels.

Stem

Short, 1.5–3 × 0.4–1 cm, usually eccentric, sometimes lateral or central, often slightly thickened at the base. Surface dry, covered with a very thin layer of short, erect, white hairs that rub off easily. No ring and no volva. Fruiting bodies may show "bleeding" of a reddish or orange liquid.

Flesh

Solid, pale pink to cream, firm, rubbery, up to 8 mm thick, not changing colour. Odour unremarkable, slightly fruity, somewhat sharply aromatic. Taste bitter (one old description gave a sweet taste). The flesh should not be tasted. Iron(II) sulfate (10% aqueous solution) stains the mature fruiting body green.

Spore print and spores

Spore print pinkish (more rarely described as cream). Spores globose to ovoid, warty (warts about 0.5–0.7 µm), thin-walled, hyaline in KOH, non-amyloid; size about 6–8.7 × 5.6–7.4 µm (descriptions give different ranges).

Habitat and distribution

Ecology. Saprotroph, a pioneer species in the colonisation of dead wood, preferring wood that is relatively little decayed. Grows singly or in groups of 2–3 fruiting bodies on dead wood of broadleaved trees, above all elms (Ulmus), also lime, maple and horse chestnut. Prefers lying, shaded trunks and logs in places that are periodically flooded. Development of the fruiting bodies requires light from the long-wavelength part of the spectrum, without any blue light.

Distribution. Circumboreal range: Europe (including Scandinavia), North Africa, eastern North America, Canada, Korea, Japan. Very rare in Poland; after a break of more than a hundred years it was recorded in the Białowieża Forest, where it is spreading; in 2020 it was known from 6 localities. In Poland it is under strict protection (Dz.U. 2014 item 1408), threat category E (endangered). On the IUCN Red List: VU (vulnerable) in Europe, NT (near threatened) globally. It appears on more than half of the European red lists of fungi; in the Baltic countries it is considered extinct or probably extinct. In Europe its decline is linked, among other things, to changes in forest use and air pollution, and locally an increase in the number of dead elms after Dutch elm disease may have favoured the species.

Fruiting. In Poland and the temperate zone of Europe mainly from August to November; in cool, damp weather (in Europe also described as extending into winter).

What can it be confused with?

• Pleurotus djamor (pink oyster mushroom) — Young fruiting bodies are similar in shape and colour, but in the oyster mushroom the gills are adnate or decurrent, whereas in the wrinkled peach they are notched or adnexed. The mature wrinkled peach has a semicircular cap, while the oyster mushroom remains flat. The oyster mushroom has no network of veins on the cap.
• Rhodotus asperior — Differs in microscopic characters: spores generally ellipsoid to nearly globose, more rough, cheilocystidia longer with slightly thickened walls. Occurs in a tropical and subtropical environment (China).

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

• Until 2013 it was the only known species of the genus Rhodotus; the second, Rhodotus asperior, was described from China.
• For its fruiting bodies to develop it needs light from the red end of the spectrum and no blue light, which sets it apart from most fungi; the colour and shape of the fruiting bodies change depending on the lighting.
• The English name "wrinkled peach" refers to the network of veins on the pink cap; it is also called "netted rhodotus" and "rosy veincap".
• In Hungary it has been legally protected since 2005, and picking it is an offence punishable by a fine.