shaggy scalycap

Like other Pholiota mushrooms, P. squarrosa has a scaly cap and stem. The cap ranges from 3 to 12 cm (1.2 to 4.7 in) in diameter, and depending on its age, can range in shape from bell-shaped to rounded to somewhat flattened. The cap color is yellowish-brown to tawny in older specimens. The scales on the cap are yellowish to tawny, and recurved. The stem is 4 to 12 cm (1.6 to 4.7 in) long by 0.5 to 1.5 cm (0.20 to 0.59 in) thick, and roughly equal in width throughout. The partial veil that covers the young gills forms a thick, woolly ring on the upper part of the stem. Above the level of the ring, the stem is bare, while below it is scaly like the cap. The gills are covered by a partial veil when young and have a greenish-brown color; mature gills are rusty brown. They are crowded closely together, attached to the stem (adnate), and usually notched (sinuate). The spore print is cinnamon or rusty brown. The spores are elliptic, smooth-walled, nonamyloid (not absorbing iodine when stained with Melzer's reagent), and measure 6.6–8 by 3.7–4.4 μm. The basidia (spore-bearing cells) are club-shaped, and four-spored, with dimensions of 16–25 by 5–7 μm. Fruit bodies have an odour described variously as resembling garlic, radish, lemon, onion, or skunk, and taste like radish.

Similar species. …

The mushroom is typically found growing in clusters at the base of trees and stumps. Pholiota squarrosa is thought to be a white rot fungus, which use cellulose as a carbon source, and have the ability to degrade the lignin (present in wood) to carbon dioxide to access the cellulose molecule. The fungus can attack a wide variety of deciduous host trees, including sugar maple, red maple, yellow birch, paper birch, American beech, and white ash. It can also attack conifers, like spruce. The fungus is a secondary parasite, in that it attacks trees that have already been weakened from prior injury or infection by bacteria or other fungi. It also functions as a saprobe, and can obtain nutrients by breaking down organic matter in dead wood. P. squarrosa is found in North America and Europe. The North American distribution extends north to Canada, and south to Mexico, where its appearance is restricted to coniferous forests. In the Netherlands, P. squarrosa is one of many mushrooms that can regularly be found fruiting on ancient timber wharves. The fruit bodies are used as a primary food source by the red squirrel Sciurus vulgaris, and have a higher protein content than the other mushrooms typically consumed by this species. Decaying fruit bodies are also used as a food source by fruit flies of the genus Drosophila.

Although some sources report P. squarrosa as edible, the mushroom has caused several cases of poisoning. The afflicted individuals had consumed alcohol with the mushroom, then experienced vomiting and diarrhoea about ten hours later. The toxic effect may be due to the combination of eating the mushrooms and taking alcohol, although the extended time delay between consumption and symptoms suggests the mechanism of toxicity is different than the antabuse effect experienced from Coprinopsis atramentaria with alcohol.