Bleach Cup

Description

The bleach cup forms a large, irregular, cup-shaped fruiting body 5–15 cm across, which splits with age and flattens out on the ground. The interior is grey-brown to dark reddish-brown, delicately wrinkled and folded into a network of veins, while the outside is whitish and mealy. The flesh is brittle and, when broken, smells distinctly of chlorine. This is the best identifying feature.

It grows in early spring, from April to May, on the ground in deciduous forests and parks, preferably on calcareous soil, singly or in groups, often on embankments and beside melting snowdrifts. Its brownish colour makes it easy to lose against the ground. It is rare in Poland.

It can be confused with cup fungi (Peziza), which have no veins and no smell of chlorine, and with Discina ancilis, which grows on coniferous wood. The bleach cup is under strict protection in Poland, so it must not be picked; it is best only to look at it and photograph it.

Identification features

Cap

Fruiting body (apothecium) 5–15 cm across, up to 20 cm according to some descriptions; when young cup-shaped and irregular, with an inrolled margin, splitting at about 7–8 cm and flattening out on the ground in older specimens. The inner surface (hymenium) is grey-brown, yellow-brown to dark reddish-brown, delicately wrinkled and, with age, folded into a vein-like pattern. The outer surface is whitish, mealy or covered with pustules, veined towards the base.

Hymenophore (underside of the cap)

Not applicable: an ascomycete with a cup-shaped fruiting body; the spore-bearing layer (hymenium) covers the inner surface of the cup. No gills, tubes or spines.

Stem

Short, poorly defined, pale grey; anchors the cup in the substrate.

Flesh

Brittle, whitish, thin. When broken it has a distinct smell of chlorine (bleach). Taste mild; the flesh should not be tasted.

Spore print and spores

Spore print colour: no data. Spores ellipsoid, smooth, without guttules, with homogeneous contents, 21–25 × 12–15 µm (descriptions give different ranges).

Habitat and distribution

Ecology. A saprotroph growing on the ground in deciduous forests and parks, according to some descriptions also in mossy litter or conifer needles under coniferous trees. Prefers calcareous soil and embankments and sheltered sites; sometimes called a fungus of the edges of melting snowdrifts.

Distribution. North America and Europe (including Bulgaria, Sweden, Spain, Wales), also Turkey, where it is considered critically endangered. Rare in Poland: by 2020, 6 historical and 27 new localities had been reported; locally not uncommon. On the Red List of Plants and Fungi of Poland it has the status R (rare, potentially threatened because of its limited range and small habitat areas). It has been under strict protection in Poland since 1983 (Dz.U. 2014 item 1408); it is not on the list of fungi approved for sale in Poland.

Fruiting. In Poland April–May; in Europe from March to May, in North America from April to June. Fruiting bodies can persist for up to about 12 weeks.

What can it be confused with?

• Discina ancilis (Polish: krążkownica wrębiasta) — Smaller, grows on decaying coniferous wood, without a smell of chlorine. The interior is more reddish-brown, wrinkled or smooth rather than veined; the outer surface has tufts of fine hairs. Spores finely warty.
• Gyromitra parma (Polish: piestrzenica tarczowata) — Also occurs on the wood of deciduous trees (mainly beech and ash), whereas the bleach cup grows on the ground.
• Peziza spp. (cup fungi) — No network of veins on the interior and no smell of chlorine; they usually fruit later. The flesh is thinner, and drops of iodine turn the flesh and ascus tips dark blue. Some cup fungi are poisonous.

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 English name bleach cup comes from the smell of chlorine noticeable when the fruiting body is broken.
• Despite its cup shape it is a close relative of the morels, belonging to the same family, Morchellaceae; hence the English name cup morel.
• It is sometimes called a fungus of melting snowdrifts, because the fruiting bodies often appear at the edges of thawing snow.
• It was described in 1801 by Persoon from specimens collected near Klagenfurt, Austria.