Yellow Brain Fungus
Tremella mesenterica
The Yellow Brain Fungus (Tremella mesenterica) is a brightly coloured jelly fungus in the family Tremellaceae, widely distributed across the temperate woodlands of the Northern Hemisphere. Despite its common name suggesting a brain-like appearance, the fruiting bodies are typically lobed, leaf-like, or convoluted masses of translucent orange-yellow to golden gelatinous tissue that can look remarkably like a lump of yellow jelly or a small cluster of wrinkled leaves. Often found on dead hardwood branches, particularly those infected with the crustose fungus Stereum hirsutum, the Yellow Brain is one of the most striking and easily recognised of all woodland fungi.
• Fruiting bodies are gelatinous, convoluted, lobed, or folded masses 2–8 cm across, bright golden-yellow to orange when fresh, becoming more translucent and orange-brown when dry
• Grows exclusively on dead hardwood, particularly birch, beech, and oak, and is almost always associated with the underlying crust fungus Stereum hirsutum (Hairy Curtain Crust)
• The genus Tremella comprises approximately 100 species of jelly fungi distributed worldwide, primarily in temperate and tropical regions
• The specific epithet mesenterica means "in the middle of the intestine," referring to the convoluted, brain-like or intestinal appearance of the fruiting body
• The fruiting body is composed of a dense, rubbery-gelatinous matrix that can rehydrate after desiccation — when dry, the fungus hardens into a small dark wrinkled mass, but revives to its bright golden form after rain
Taxonomy
• Found throughout Europe from the British Isles and Scandinavia to the Mediterranean
• Distributed across Russia, Siberia, China, Japan, and Korea
• In North America, widespread across temperate and boreal forests from Canada through the United States
• Also recorded from Australia, New Zealand, and parts of South America
• Grows on dead hardwood branches, particularly birch (Betula), beech (Fagus), and oak (Quercus)
• The species is never found on conifers — its host range is strictly broadleaved (angiosperm) wood
• Fruiting typically occurs in autumn and winter, particularly after heavy rainfall, and can persist through mild winters
• The fungus is first recorded in European mycological literature from the 16th century, though it was undoubtedly known to foragers long before that
• Fruiting bodies are gelatinous, rubbery, lobed, folded, or convoluted masses 2–8 cm across, and 1–4 cm thick
• Bright golden-yellow to orange when fresh and hydrated, becoming translucent and more orange-brown as they dehydrate
• When completely dry, the fruiting body shrinks dramatically into a hard, dark orange, wrinkled crust that can revive after rain
• Surface smooth to slightly wrinkled, often lobed or brain-like in appearance
• Inner tissue is gelatinous, translucent, and somewhat rubbery
• Spore-producing surface (hymenium) is the outer surface of the gelatinous lobes
• Fruity odour when fresh; taste mild and insipid
Microscopic Features:
• Basidia (spore-producing cells) longitudinally septate (divided), 4-celled
• Spores ellipsoid, smooth, hyaline, 8–12 × 6–8 μm, produced on long sterigmata (projections) from the basidia
• Spore print white
Habitat and Host:
• Grows on dead branches of hardwood trees, particularly where bark has fallen away
• Almost always found on wood already colonised by the crustose fungus Stereum hirsutum (Hairy Curtain Crust)
• Tremella mesenterica is not actually parasitic on the wood itself — it is a mycoparasite (parasite of another fungus), specifically feeding on the Stereum hirsutum mycelium growing within the wood
Lifecycle:
• Produces fruiting bodies after rain when moisture is sufficient to trigger spore production and basidiospore release
• Spores germinate to form a yeast-like budding stage before establishing mycelium in suitable hardwood substrate
• Mycelium invades and parasitises Stereum hirsutum, eventually producing visible fruiting bodies
Habitat:
• Grows on dead hardwood branches, typically attached to fallen or standing dead wood in deciduous and mixed woodlands
• Requires high humidity and consistent moisture — most commonly found after prolonged wet weather
• Appears in autumn and winter in temperate regions, but can persist through mild winters
Ecological Role:
• Mycoparasitic — feeds on the mycelium of Stereum hirsutum, a crustose saprotrophic fungus that decomposes hardwood
• By parasitising Stereum, Tremella may reduce the rate of wood decay in dead branches, indirectly affecting the speed at which carbon is returned to the soil
• Fruiting bodies are consumed by some woodland invertebrates, though the gelatinous texture is not particularly attractive to most animals
Adaptations:
• Gelatinous fruiting bodies can dehydrate completely and rehydrate multiple times, allowing persistence through variable moisture availability
• Bright golden colour may attract insects that inadvertently assist in spore dispersal
• Mycoparasitic lifestyle allows Tremella to exploit an ecological niche without competing directly with wood-decay fungi for the same substrate
Edibility:
• Considered edible when young and fresh — the gelatinous fruiting body has virtually no flavour and a crunchy-chewable texture when raw
• In traditional Chinese medicine, Tremella species are valued for their supposed health-promoting properties
• Commonly used in Chinese cuisine, particularly in soups, stir-fries, and desserts where its gelatinous texture is prized
• Often compared texturally to sea cucumber (trepang) in Chinese cuisine
Preparation:
• Clean thoroughly in cold water to remove any debris or bark particles
• Slice or tear into pieces and cook in soups, stir-fries, or stews
• The fungus will soften further when cooked but retains its gelatinous character
• Absorbs the flavours of other ingredients well due to its neutral taste
Warning:
• Only consume when identified with absolute certainty — while T. mesenterica is edible, misidentification with other jelly fungi is possible
• Never consume any wild fungus unless you are an experienced mycologist or have received expert identification
Harvesting:
• Fruiting bodies appear after rain in autumn and winter on dead hardwood, particularly birch, beech, and oak
• Harvest when fresh and hydrated — dry, shrivelled specimens are less palatable
• Use a sharp knife to cut the fruiting body from the substrate, taking care not to damage the underlying mycelium or Stereum host
• Clean immediately after harvest by gentle rinsing in cold water
Processing:
• Soak dried specimens in warm water for 20–30 minutes to rehydrate
• Fresh specimens should be used within a few days or dried for later use
• Drying produces a dark orange, hard mass that will rehydrate when soaked
Cultivation:
• Not commercially cultivated due to its mycoparasitic nature and gelatinous texture, which is not highly valued in Western markets
• Could potentially be cultivated on hardwood logs inoculated with both Stereum hirsutum and Tremella mesenterica, but this is not economically viable
Use in Cuisine:
• Traditional Chinese medicine and cuisine value Tremella species as a health tonic
• Used in soups and broths, where its gelatinous texture is desirable
• Occasionally used as a textural ingredient in salads and cold dishes when young and fresh
Culinary:
• Eaten in China and other East Asian countries for its gelatinous texture and supposed health benefits
• Used in vegetarian cuisine as a substitute for meat-based gelatinous ingredients
• Considered a cooling food in traditional Chinese medicine, often used in soups and desserts
Traditional Medicine:
• Used in traditional Chinese medicine to promote respiratory health, improve skin condition, and boost immunity
• Related species (particularly Tremella fuciformis, the Snow Fungus or White Wood Ear) are more commonly used commercially
• Not a major medicinal species in its own right, but included in some traditional herbal preparations
Fun Fact
The Yellow Brain Fungus is one of the most bizarre and otherworldly organisms in the woodland — a bright golden, wrinkled, gelatinous mass that can shrivel to a dark crust in dry weather and then magically re-inflate to its full glowing glory within hours of rain, looking like a chunk of sunshine that has fallen from the sky and landed on a dead branch. • Tremella mesenterica is not actually a parasite of the wood it grows on, but a parasite of another fungus — specifically, it invades the mycelial network of Stereum hirsutum (Hairy Curtain Crust) within the dead wood. This makes it one of the relatively few known mycoparasitic fungi — a fungus that eats other fungi • The fruiting bodies can completely dry out, shrinking to a small, dark, wrinkled crust less than 5% of their fresh volume, and then rehydrate and expand to their full size within just a few hours of rain, a remarkable example of drought resistance in the fungal world • In traditional Chinese cuisine, Tremella species including T. mesenterica are collectively known as "White Wood Ear" (Bai Mu Er) or "Snow Fungus," though the true Snow Fungus is Tremella fuciformis — both species share the prized gelatinous texture • The specific epithet mesenterica literally means "of the mesentery" — the membrane attaching the intestine to the abdominal wall — because the convoluted, folded fruiting body was thought to resemble intestinal membranes. This vivid (if slightly unappetising) comparison was made by the great Swedish mycologist Elias Magnus Fries in the early 19th century • Despite its brain-like common name, T. mesenterica is not closely related to the true "brain fungi" (species of Gyromitra or Discinaceae) — those are cup fungi in the phylum Ascomycota, whereas Tremella is a jelly fungus in the phylum Basidiomycota
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