Mushrooms on trees are the visible reproductive structures of fungi, often called lignicolous fungi. These organisms form an expansive, thread-like network called mycelium that permeates the wood. Fungi absorb nutrients from organic matter, and the fruiting bodies we see indicate a much larger organism playing a role in forest ecology.
The Ecological Roles of Tree Fungi
The appearance of a mushroom on a tree signifies one of two primary relationships. Most tree-dwelling fungi are saprobic, deriving nutrition from dead or decaying wood. These organisms act as nature’s recyclers, secreting enzymes that break down complex wood compounds like cellulose and lignin. This decomposition is fundamental to the forest ecosystem because it prevents the endless accumulation of debris and returns locked-up nutrients back into the soil.
The second ecological role is that of a parasitic fungus, which obtains nutrients from a living tree. Parasitic fungi typically gain entry through a wound or weak point, establishing their mycelium within the living tissue. This infection can lead to internal decay, compromising the tree’s structural integrity. While parasitic fungi can cause disease, they are a natural part of forest dynamics, often targeting old, weak, or stressed individuals.
Common Species Found on Deciduous Trees
Deciduous trees (hardwoods) host a diverse range of fungi. Oyster mushrooms (Pleurotus ostreatus) are common, recognizable as clusters of fan or shelf-shaped caps growing on dead or dying hardwoods like oak and beech. Their caps vary from white to gray or brownish, and they possess pale gills that run down a very short or absent stem.
Lion’s Mane (Hericium erinaceus) is unique for its shaggy, white appearance, resembling a cluster of icicles or a pom-pom. This species acts as both a parasite and a saprobe, often found on injured or dying trees such as maple, beech, and oak, where it causes white rot. It typically fruits high up on the trunks of older trees or from exposed wounds.
Turkey Tail (Trametes versicolor) is a widespread saprobic species that decomposes deciduous logs and stumps. This bracket fungus is thin and flat, growing in tiered, overlapping layers. It displays concentric zones of various colors, including browns, grays, and blues, resembling a turkey’s tail feathers. Unlike gilled mushrooms, Turkey Tail is a polypore, releasing spores from tiny pores on the pale underside of the fruiting body.
Common Species Found on Coniferous Trees
Coniferous softwoods, such as pines, spruces, and firs, support fungal species adapted to their resinous composition. The Cauliflower Fungus (Sparassis species) appears as a large, globular mass of flattened, wavy, frilly branches. This parasitic fungus usually targets the base of conifers, causing damaging brown rot in the root system and lower trunk.
Dyer’s Polypore (Phaeolus schweinitzii) is a large shelf fungus that primarily affects conifers like pine and spruce. Named for the bright yellow dye it can yield, it has a velvety texture with colors ranging from yellow-orange to dark brown as it ages. This species is both parasitic and saprobic, attacking the roots of living trees and causing serious butt and heartwood rot.
Angel Wings (Pleurocybella porrigens) are delicate, white, fan-shaped mushrooms that grow in shelving clusters on the dead wood of conifers. They are thin and flexible, often confused with some oyster mushroom species due to their shape. As a saprotroph, its presence indicates the decomposition of a fallen conifer log or stump.