Black-staining Polypore

Meripilus sumstinei

Type: polypore

Black-staining Polypore

Physical Characteristics

Large, overlapping fan-shaped caps that are ochre to tan in color with brown scales or zones. One of its most distinctive physical features is that the white pore surface and flesh stain dark gray to black when bruised or handled.

Habitat & Growing Conditions

Typically found at the base of living deciduous trees, especially oaks, or growing from buried roots and stumps.

Season & Fruiting Time

Late summer and autumn.

Similar Looking Species

Grifola frondosa (Hen of the Woods) which does not stain black and has smaller caps; Bondarzewia berkeleyi (Berkeley's Polypore) which is larger, thicker, and does not stain black.

Ecological Role

Saprophytic on dead wood and parasitic on the roots of living hardwoods, causing white rot.

Fruiting Body

Consists of large, multi-capped rosettes. Individual caps are fan-shaped, flattened, with wavy margins. The upper surface is dry and finely velvety when young, becoming smoother and zoned with age. The hymenophore consists of white to cream-colored pores on the underside. The stipe is usually a thick, fused common base.

Size

Rosettes can reach 30-100 cm in diameter; individual caps are typically 5-20 cm wide.

Spore Print

White

Distribution

Common in Eastern North America and similar climates.

Identification Tips

The most reliable field test is to bruise the white pore surface or cut the flesh and wait 15-30 minutes for it to turn distinctly black.

Interesting Facts

The genus Meripilus is known for creating some of the largest fruiting bodies among fungi. The species is named 'sumstinei' in honor of the American mycologist David Sumstine. It plays a significant role in nitrogen cycling within forest ecosystems by breaking down complex wood fibers in wood.

Safety reminder

AI mushroom identification is a best-effort estimate and can be wrong. Never use it to decide whether a mushroom is safe to handle or eat — always confirm with a qualified mycologist before any consumption.

Identified on: 5/1/2026

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