Peniophora rufa

Peniophora rufa, commonly called Red Tree Brain Fungus, is a corticioid wood-decay fungus recognized by its small cinnabar-colored cushions and wrinkled, brain-like surface. It grows directly on the bark of dead hardwood branches, where clusters often follow cracks or ridges in the wood. The species is widely distributed across temperate forests and is frequently encountered on fallen oak twigs and other hardwood debris.

Growth Form

The fruiting body forms small cushion-like patches that are closely attached to bark. Individual patches may appear rounded, irregular, or slightly lobed, often merging into small clusters.

The surface is typically wrinkled or shallowly folded, giving it a brain-like appearance. When moist, the fungus can appear slightly soft or fleshy; when dry it becomes firmer and darker in color.

Colors range from orange-red to brick red or cinnabar, sometimes fading toward dull brown as the fruiting bodies age.

Substrate and Habitat

Peniophora rufa grows on dead hardwood bark and small branches, especially on fallen twigs or standing dead wood. Oak is a common host, though other hardwoods may also be colonized.

The species typically appears in woodland environments, where fallen branches provide suitable substrate for wood-decay fungi. Fruiting bodies may develop during cool, moist periods and can persist through winter.

Fruiting Surface

As a corticioid fungus, Peniophora rufa produces spores on a smooth to wrinkled hymenial surface rather than forming caps, gills, or pores.

The fertile surface covers the visible cushions of the fungus and may show:

• Wrinkles or folds
• Shallow dimples
• Irregular lobing along bark fissures

These features give the species its common name “Red Tree Brain Fungus.”

Spores and Microscopic Features

Microscopic examination reveals smooth, colorless basidiospores produced on basidia within the hymenial layer. Additional microscopic characters such as cystidia and hyphal structure are often used to confirm identification within the genus.

Because many corticioid fungi appear similar in the field, microscopic traits are sometimes required for definitive identification.

Ecology and Role

Peniophora rufa is a saprotrophic wood-decay fungus, breaking down dead hardwood bark and contributing to nutrient cycling within forest ecosystems. By decomposing woody material, it helps return carbon and minerals to the soil.

The species is also notable as a host fungus for certain parasitic jelly fungi, including Tremella mesenterica (Witch’s Butter), which develops by parasitizing corticioid fungi such as Peniophora.

Similar Species

Several fungi growing on bark can resemble Peniophora rufa at first glance.

• Tremella mesenterica – a gelatinous yellow to orange jelly fungus that often parasitizes Peniophora. It has a translucent, lobed structure rather than a matte, fleshy surface.
• Peniophora incarnata – another corticioid species with reddish tones but typically forming thinner crusts rather than discrete cushions.
• Dacrymyces species – jelly fungi that form orange blobs on wood, usually more translucent and gelatinous.

Texture is often the most useful field clue:
Peniophora rufa is matte and leathery, while jelly fungi are soft, translucent, and gelatinous.