How to identify Giant Polypore

To correctly identify Giant Polypore (Meripilus giganteus), check each of these features in order. Misidentification is the most common cause of mushroom poisoning, so cross-reference multiple sources.

Step-by-step identification

1. 1

   Cap

   Shape, color, surface texture, and diameter.

   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.

2. 2

   Gills

   Attachment to stem, color, and spacing.

   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.

3. 3

   Stem

   Length, shape, surface, and any ring.

   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.

4. 4

   Flesh

   Color, texture, and bruising reaction.

   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.

5. 5

   Fruiting body

   Overall growth pattern.

   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.

6. 6

   Habitat

   Where it grows and on what substrate.

   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.

Fruit body characteristics

• Gill attachment: Not gilled; has a pore surface.
• Stem shape: No true stem; individual caps arise from a common, stout, often buried base.
• Stem surface: N/A (no true stem)
• Ring: Absent
• Stem cross-section: N/A (no true stem)

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