Polypore mushrooms are a diverse group of fungi, often recognized by their distinctive shelf-like or bracket-like forms growing on trees. These organisms are widespread across global forests, where they play various roles in their ecosystems.
What Defines a Polypore Mushroom
Polypore mushrooms are defined by their spore-producing surface, called the hymenophore, which is covered in small tubes or pores rather than gills. These pores are found on the underside of the fruiting body, forming a honeycomb-like structure. The name “polypore” comes from Greek words meaning “many pores,” directly referencing this feature.
The texture of polypores is tough, woody, or leathery, differing from the softer, fleshy texture of many gilled mushrooms. They grow directly from wood without a traditional stem, appearing as shelves, brackets, or flat crusts on tree trunks, logs, or stumps. While some species may have a cap and a stalk, this is not a universal trait. Polypores exhibit various shapes, sizes, and colors, from small patches to large, multi-tiered brackets.
Their Role in Ecosystems
Polypore mushrooms serve as decomposers of wood, playing a role in forest ecosystems. They break down complex wood components like lignin and cellulose, which are the main building blocks of plant cell walls, and return these nutrients to the soil. This process of nutrient cycling is important for forest health and aids in carbon dioxide absorption.
Wood-decaying polypores are categorized into two types based on their decomposition methods: white rot fungi and brown rot fungi. White rot fungi break down both lignin (which is brown) and cellulose (white), resulting in wood that appears whitish and has a fibrous texture. These fungi use enzymes for this breakdown.
In contrast, brown rot fungi degrade cellulose, leaving behind the brown lignin. The decayed wood takes on a brownish hue and cracks into cuboidal pieces. Brown rot fungi are common in coniferous forests, though they can also be found on hardwoods like oak. The presence of polypores, whether parasitic on living trees or saprotrophic on dead wood, is a natural part of the cycle of decay and regeneration in forests.
Finding and Identifying Polypores
Polypore mushrooms can be found in forests, woodlands, and urban landscapes, growing on dead or living trees, logs, and stumps. Their growth patterns vary, appearing as solitary specimens, in overlapping shelves, or in rosette formations. The best time to observe many polypores is from late summer to autumn, when moisture and temperature conditions are favorable for their fruiting bodies to develop.
Identification involves observing macro-features such as the size, shape, and color of the fruiting body. The color and arrangement of the pores on the underside are important, as pore size and shape can vary between species, from tiny and round to maze-like or angular. Noting the host tree is also a clue, as some polypores are specific to certain tree species like birch or oak, while others grow on a wider range of hosts. Precise identification can be complex and may require consulting field guides or expert knowledge, given the diversity of species.
Polypores and People
Humans have interacted with polypore mushrooms for thousands of years, with diverse applications ranging from medicinal uses to practical crafts. Ötzi the Iceman, a natural mummy dating back over 5,000 years, carried birch polypore, which researchers believe he used to combat intestinal parasites. The tinder polypore (Fomes fomentarius) was also found among his supplies, used for fire-starting due to its ability to catch and maintain an ember.
Many polypore species are valued for their medicinal properties. Reishi (Ganoderma lucidum) and Turkey Tail (Trametes versicolor) are known for their traditional use in various cultures and are subjects of scientific interest for their compounds, including triterpenes and polysaccharides, which show promise in immune support and anti-cancer research. Some polypores are also edible, such as Chicken of the Woods (Laetiporus sulphureus) and Dryad’s Saddle (Cerioporus squamosus), though caution is always advised, as consuming unidentified fungi can be dangerous. Beyond consumption and medicine, the tough, leathery texture of certain polypores has led to their use in crafts, such as making “amadou” (mushroom felt) for clothing or as a razor strop.