The Black Staining Polypore (Meripilus sumstinei) is a large, cluster-forming fungus found throughout North America, particularly east of the Rocky Mountains. It is known for its impressive size and distinctive growth pattern at the base of trees. The defining characteristic of this fungus is a dramatic color change that occurs upon handling. This article examines the appearance and habitat of this mushroom and its suitability for the table.
Visual Identification and Habitat
The Black Staining Polypore grows as a large, rosette-shaped cluster composed of numerous overlapping, fan-shaped caps, which collectively can span two feet or more in width. When young, the surface of the individual caps is a pale, creamy white or tan color, often with muted concentric zones. These caps are typically thickest near the base and become thinner toward the wavy, outer margin.
The undersurface of the mushroom consists of a fine pore layer rather than gills, which is initially white or cream-colored. This pore surface and the internal flesh hold the fungus’s most important identifying feature: the black staining reaction. When the tissue is cut, scratched, or bruised, it quickly darkens to a brown or black color, often within just a few minutes. This immediate staining is a reliable field test that separates Meripilus sumstinei from similar species.
This polypore is found during the summer and early fall months. It grows as a parasitic fungus at the base of living hardwood trees or as a saprophyte on stumps and buried roots, often associated with oak trees. The fungus causes butt rot in the host tree. It often reappears in the same location year after year as long as the wood provides nutrients.
Edibility Verdict and Essential Safety Precautions
The Black Staining Polypore is considered edible, but this assessment comes with a significant qualification regarding its age and texture. Only young, fresh specimens are recommended for consumption, as the flesh rapidly becomes tough, leathery, and woody as the mushroom matures. Foragers should seek out clusters that are still relatively small and whose fronds are soft and pliable, often no wider than four or five inches.
Older, tougher specimens may still be used to create flavorful mushroom broth or stock. Consuming fibrous material can sometimes lead to mild gastrointestinal upset, such as nausea or cramping, in sensitive individuals. To mitigate this and break down the chitin in the fungal cell walls, all wild mushrooms, including this polypore, require thorough cooking.
It is important to accurately distinguish this species from other large, cluster-forming polypores. A common look-alike is Grifola frondosa, known as Hen of the Woods or Maitake, which is also edible but appears later in the fall and does not exhibit the black staining reaction. Another similar fungus is Berkeley’s Polypore (Bondarzewia berkeleyi), which shares the large, rosette form but remains a cream or tan color even when handled.
Starting with a small portion the first time any wild mushroom is consumed is a sensible precaution to gauge individual tolerance. This practice helps ensure that any unique sensitivity or allergic reaction is quickly identified before a larger meal is prepared.
Preparing and Cooking the Polypore
Successful preparation begins with selective harvesting, focusing only on the soft, tender outer margins of the fungal cluster. The tough, central core and any parts that feel rubbery or fibrous should be trimmed away and discarded, or reserved solely for making stock. This focus on the tender edges is the primary way to ensure a pleasant eating texture.
The edible portions should be cleaned gently, often by rinsing, and then sliced thinly to further reduce potential chewiness. Slicing the fronds into small strips or juliennes is particularly helpful for methods like sautéing or stir-frying. When cooked, the Black Staining Polypore develops a rich, earthy, and sometimes slightly tangy flavor profile, often compared to a meaty or umami-rich broth.
The black-staining property continues during the heating process. The mushroom tissue will turn a dark gray or black color as it cooks, which does not affect the flavor. This characteristic makes it a unique ingredient, suitable for dishes where a dark, rich color is acceptable, such as savory tarts, duxelles, or deeply flavored ramen broths.