Yellow brainTremella mesenterica

Tremella, or "yellow brain" (Tremella mesenterica, in English-speaking countries "yellow brain mushroom", "witch's butter") is a distinctive bright yellow jelly fungus with a wavy, folded shape that looks like a brain or a yellow jelly pudding. The Latin epithet mesenterica means "intestine-like, folded" (from Greek mesenterion, "the mesentery"), a nod to its distinctive shape.

Fruiting body 3-10 cm across, gelatinous, soft, attached to the substrate by its back with no distinct stem. In wet weather it is clearly jelly-like, soft, with a glossy surface; in dry weather it shrivels, hardens and turns horny, and once moistened it comes back to life and regains its shape. Color bright yellow, lemon yellow, orange-yellow.

Edible — mycological communities list it as edible with limitations: it is bland raw (no distinct taste), but soaks up flavors well and is used in soups and sauces as a thickener and decorative ingredient. In traditional Chinese and Japanese cuisine Tremella is used widely: in sweet soups with berries, in tonic broths, in cosmetic masks (natural hyaluronic acid). In Europe it is less popular and rarely gathered, mostly for culinary experiments.

A distinctive ecological trait — Tremella mesenterica it parasitizes the mycelium of other fungi of the genus Peniophora (thin-skinned crust fungi on wood). So it is not an independent saprotroph but a mycoparasite on fungi that grow on wood. That's why it only grows where Peniophora is present, mostly on fallen branches and trunks of broadleaf trees.

Key features of Tremella mesenterica: Bright yellow gelatinous fruiting body with a wavy, folded shape No stem, attached to the substrate by its side Soft in wet weather, hardens in dry weather, recovers once moistened Spore print white Smell faint, neutral Grows on fallen branches and trunks of broadleaf trees (oak, beech, hornbeam, birch) Flesh gelatinous, with no distinct taste

The main risk is confusing it with its close relative Tremella aurantia (also a yellow jelly, but thicker and less folded, on conifer wood, parasitic on a different crust fungus, Stereum hirsutum, considered inedible). Also with Calocera viscosa (a small orange-yellow coral-like fruiting body on conifer stumps, not jelly-like) and with Bisporella citrina (small yellow disc-shaped ascomycetes on wood).

In Ukraine, Tremella mesenterica is common in broadleaf and mixed forests: the Carpathians, Prykarpattia, Polissia, the forest-steppe. Season: year-round — the fruiting bodies withstand drying out and rewetting, so you can find them even in winter during thaws.