How to identify Common Rustgill

To correctly identify Common Rustgill (Gymnopilus penetrans), 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 2-8 cm in diameter, convex to broadly convex or nearly flat with age, sometimes with a low umbo. The color ranges from rusty orange, tawny, or yellowish-brown to reddish-brown, often darker towards the center. The surface is dry, finely fibrillose to scaly, especially when young, becoming smoother with age. The margin is often incurved when young, becoming straight or slightly wavy.

2. 2

   Gills

   Attachment to stem, color, and spacing.

   The gills are adnate to adnexed, sometimes with a slight decurrent tooth, crowded, and relatively narrow. They are initially yellowish to pale orange, becoming rusty orange to cinnamon-brown as the spores mature. There are numerous lamellulae (short gills).

3. 3

   Stem

   Length, shape, surface, and any ring.

   The stem is 3-10 cm long and 0.5-1.5 cm thick, central, cylindrical, often slightly tapering towards the base or equal. The color is similar to the cap, yellowish to rusty brown, often paler near the apex and darker towards the base. The surface is fibrillose, sometimes with remnants of a partial veil forming an indistinct fibrillose ring zone that quickly disappears. The stem is solid when young, becoming hollow with age.

4. 4

   Flesh

   Color, texture, and bruising reaction.

   The flesh is yellowish to pale orange-brown, firm in the cap, and fibrous in the stem. It has a distinctly bitter taste and a mild, sometimes slightly fungoid or radish-like odor.

5. 5

   Fruiting body

   Overall growth pattern.

   The fruiting body is a typical agaric (gilled mushroom) with a cap, gills, and a central stem. It often grows in clusters or scattered groups.

6. 6

   Habitat

   Where it grows and on what substrate.

   Saprobic, growing on decaying conifer wood (especially pine, spruce, and fir), often on stumps, logs, or buried wood. It can also be found on deciduous wood less frequently. It grows solitarily, scattered, or in clusters.

Key Facts

Cap surfaces

Dry, finely fibrillose to scaly, becoming smoother.

Growth Form

Solitary, scattered, or in clusters.

Spore Print

Rusty orange to cinnamon-brown.

Body color

Rusty orange, tawny, yellowish-brown to reddish-brown.

Odor

Mild, sometimes slightly fungoid or radish-like.

Flesh bruises

Does not bruise significantly.

Height

3-10 cm

Cap Diameter

2-8 cm

Fruit body characteristics

• Gill attachment: Adnate to adnexed, sometimes with a slight decurrent tooth.
• Stem shape: Cylindrical, often slightly tapering towards the base or equal.
• Stem surface: Fibrillose, sometimes with an indistinct fibrillose ring zone.
• Ring: Absent or an indistinct, quickly disappearing fibrillose ring zone.
• Stem cross-section: Solid when young, becoming hollow with age.

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