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Meripilus giganteus, commonly known as the Giant Polypore or Black-staining Polypore, is a large, parasitic and saprobic bracket fungus belonging to the family Meripilaceae. It is characterized by its massive size, consisting of numerous overlapping, fan-shaped or spatulate caps arising from a common, thick base. The fruiting body can grow to impressive dimensions, often reaching over a meter in width and weighing several kilograms. Its color typically ranges from pale cream to yellowish-brown, darkening with age and bruising to black. It is a significant white-rot fungus, primarily found at the base of deciduous trees, particularly oak and beech, causing a white rot in the heartwood.
How to Identify
- Cap
- Individual caps are fan-shaped, spatulate, or kidney-shaped, 10-60 cm (4-24 inches) wide and 1-3 cm (0.4-1.2 inches) thick. The surface is finely velvety or smooth, often radially wrinkled, and can be zoned. Color ranges from pale cream, yellowish-tan, or buff when young, becoming darker brown, grayish-brown, or even blackish with age. The margins are thin and often wavy. A key diagnostic feature is that the caps and pores bruise dark brown to black when handled or damaged.
- Gills
- Not gilled. The underside of the caps features a pore surface. The pores are very small, 3-5 per millimeter, circular to angular, and white to cream-colored when young, becoming yellowish or brownish with age. They bruise dark brown to black instantly upon touch.
- Stem
- There is no true stem. The individual caps arise from a stout, common, often subterranean or partially buried stipe-like base that is tough and fibrous.
- Flesh
- The flesh is thick, fibrous, tough, and white. It darkens to pinkish-brown and then black when cut or bruised, especially in older specimens. It has a mild, slightly acidic taste and a pleasant, mushroomy odor when young, becoming more acrid with age.
- Fruiting body
- The fruiting body is a large, compound structure composed of numerous individual, fan-shaped or spatulate caps (pilei) that are fused at a common, thick, often buried base. It can reach up to 100 cm (40 inches) or more in diameter and weigh over 50 kg (110 lbs). The overall shape is typically a large, rosette-like cluster.
- Habitat
- Saprobic and parasitic, growing at the base of living or dead deciduous trees, particularly oak (Quercus spp.), beech (Fagus spp.), and sometimes maple (Acer spp.) or other hardwoods. It causes a white rot in the heartwood of its host. It can also be found on buried roots or stumps.
Key Facts
- Cap surfaces: Finely velvety to smooth, often radially wrinkled, sometimes zoned.
- Growth Form: Large, compound cluster of overlapping, fan-shaped brackets from a common base.
- Spore Print: White to pale cream.
- Body color: Pale cream to yellowish-brown, darkening to grayish-brown or black with age and bruising.
- Odor: Mild, pleasant, mushroomy.
- Flesh bruises: Rapidly dark brown to black.
- Height: Up to 50 cm (20 inches) from base to top of cluster.
- Cap Diameter: Individual caps 10-60 cm (4-24 inches) wide; entire cluster up to 100 cm (40 inches) or more.
- Nutrient gathering: Parasitic and saprobic.
Safe
SafeMeripilus giganteus is generally considered edible when young and tender, but it can cause gastrointestinal upset in some individuals, especially if consumed in large quantities or if older, tougher specimens are eaten. It is not known to contain deadly toxins. However, caution is advised, and it should always be thoroughly cooked. Some people report a laxative effect.
Quick Check
- Odor: Mild, pleasant, mushroomy when young; slightly acrid when old.
- Fruiting: Late summer to autumn.
- Substrate: Base of living or dead deciduous trees (especially oak and beech), or buried roots/stumps.
Where to Find
Base of Deciduous Trees
Most commonly found at the base of large, mature deciduous trees, especially oak and beech. Look for it emerging from the soil directly adjacent to the trunk or from exposed roots.
Buried Roots and Stumps
Can also fruit from buried roots or old stumps of deciduous trees, sometimes appearing to grow directly from the ground away from a visible tree trunk.
Forests and Woodlands
Abundant in broadleaf forests and woodlands across its geographic range.
Finding Tips
Seasonal Availability
Typically fruits from late summer through autumn (August to November in the Northern Hemisphere), but can occasionally be found earlier or later depending on local climate conditions.
Look for Large Clusters
Due to its size, it's often quite conspicuous. Scan the base of large deciduous trees for large, rosette-like clusters of overlapping brackets.
Check for Bruising
A definitive identification feature is the rapid blackening of the pores and flesh when bruised or cut. Gently press the pore surface to observe this reaction.
Examine the Host Tree
Note the type of tree it is growing on or near. While primarily on oak and beech, it can occur on other hardwoods.
Similar Species
Hen of the Woods
Polypore mushroom
Also known as: Maitake, Grifola frondosa
Black-staining Polypore
Polypore mushroom
Also known as: Meripilus sumstinei
Scientific Classification
- Phylum
- Basidiomycota
- Class
- Agaricomycetes
- Order
- Polyporales
- Family
- Meripilaceae
- Genus
- Meripilus
Storage Information
- Max Temperature: 4°C
- Freezing duration: 6 months
- Min Temperature: 0°C
- Refrigeration: 5 days
How to Clean
Due to its growth habit at the base of trees, Meripilus giganteus can accumulate soil and debris. Carefully brush off any dirt with a soft brush or cloth. Avoid washing with water if possible, as the pores can absorb water and become soggy. If necessary, a quick rinse and immediate drying are recommended. Trim away any tough, woody, or insect-damaged portions, especially from older specimens.
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