How to identify Winter Polypore

To correctly identify Winter Polypore (Polyporus brumalis), 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.

   The cap is typically 2-10 cm (0.8-4 inches) in diameter, circular to kidney-shaped, convex to flat, often with a central depression. The margin is usually thin and often wavy or lobed. The color ranges from yellowish-brown to dark brown or grayish-brown, often darker towards the center. The surface is dry, smooth to finely scaly or velvety, especially when young.

2. 2

   Gills

   Attachment to stem, color, and spacing.

   Pore surface is white to cream, becoming yellowish or brownish with age. Pores are angular to round, 2-4 per millimeter, often somewhat elongated radially near the stem. Tubes are shallow, 1-3 mm deep.

3. 3

   Stem

   Length, shape, surface, and any ring.

   The stem is central to eccentric, 1-6 cm (0.4-2.4 inches) long and 0.3-1 cm (0.1-0.4 inches) thick. It is typically dark brown to blackish at the base, becoming paler brown towards the cap. The surface is finely velvety to scaly, especially when young, often becoming smoother with age. It is tough and fibrous.

4. 4

   Flesh

   Color, texture, and bruising reaction.

   The flesh is thin, tough, leathery, and white to cream-colored, unchanging when bruised or cut.

5. 5

   Fruiting body

   Overall growth pattern.

   The fruiting body is a stipitate (stemmed) polypore, typically annual, growing solitary or in scattered groups.

6. 6

   Habitat

   Where it grows and on what substrate.

   Saprobic on dead hardwood, particularly fallen branches and logs of deciduous trees such as oak, beech, birch, and maple. Rarely found on conifers.

Key Facts

Cap surfaces

Dry, smooth to finely scaly or velvety.

Growth Form

Solitary or scattered, stipitate (stemmed).

Spore Print

White.

Body color

Cap: Yellowish-brown to dark brown or grayish-brown. Stem: Dark brown to blackish at base, paler towards cap. Pore surface: White to cream.

Odor

Mild, fungoid, or indistinct.

Flesh bruises

Does not bruise.

Height

Cap diameter 2-10 cm (0.8-4 inches), Stem length 1-6 cm (0.4-2.4 inches).

Cap Diameter

2-10 cm (0.8-4 inches).

Fruit body characteristics

• Gill attachment: Pore surface, not gilled.
• Stem shape: Cylindrical, often tapering slightly towards the base.
• Stem surface: Finely velvety to scaly, becoming smoother.
• Ring: Absent.
• Stem cross-section: Solid, fibrous.

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