Silky Parchment

Stereum striatum is the smallest and palest of the common Stereum fans. Its brackets rarely exceed 2 cm across, and their upper surface has a fine silky sheen with delicate radial striations and narrow concentric zones — the combination that gives the species both its scientific and English names.

Colours are restrained compared with the orange and tawny members of the genus: whitish, silvery grey, pale buff and faint tan, with a cream to whitish fertile surface. Like all Stereum, the underside is entirely smooth, with no pores, teeth or wrinkles, and in this species it is notably pale and even.

The fungus is best known from eastern North America, where it is closely associated with American hornbeam (musclewood) and related trees, and it can carpet the fine dead branches of those species in continuous rows of tiny overlapping fans. It fruits at any time of year when the wood is wet, drying to a hard, papery crust that revives after rain.

Fruit body

Caps are 0.5–2 cm wide, thin, leathery and fan- to shell-shaped, attached at a narrow lateral base. They occur in dense rows and overlapping tiers along slim branches, often fusing at their edges into a continuous frilled band, with a resupinate portion behind on shaded surfaces.

Upper surface

Finely silky to appressed-hairy, with a distinct sheen and fine radial lines, and marked with narrow concentric zones. Colours are white, silvery grey, pale buff or faintly tan, sometimes with a slight ochre band near the base. The margin is thin, wavy and typically whitish.

Fertile surface and flesh

The underside is smooth and unbroken, white to pale cream or faintly buff, occasionally with a slight pinkish or ochre cast in age. It does not release red liquid when scratched and does not stain yellow. The flesh is very thin, tough and pliant, drying hard and papery. The spore deposit is white.

Silky Parchment fruits on dead hardwood, showing a strong preference for hornbeam (Carpinus) and hop-hornbeam (Ostrya), and also occurring on beech, oak, maple and other broadleaf trees. It favours slim dead branches and small trunks, both fallen and still attached in the understorey.

Dried fruit bodies remain on the wood throughout the year, with fresh growth appearing whenever the wood stays wet, most reliably from autumn to spring. The species is common in eastern North American deciduous forest and is reported from other temperate regions.

The fungus is a saprotroph causing a white rot in fine and medium hardwood branches, degrading lignin along with cellulose so that decayed wood becomes pale and fibrous. Its specialisation on small-diameter wood places it among the fungi responsible for recycling the branch litter layer of deciduous forest.

It frequently colonises branches that die while still attached to a living understorey tree, so long rows of fans on standing dead limbs are typical. The tough, papery fruit bodies withstand freezing and desiccation, persisting for a season or more and resuming spore production once rewetted.

Stereum complicatum grows in similarly crowded rows on hardwood branches but is a clear orange-tan on both surfaces and has a duller, less silky upper side. Stereum ostrea is much larger, with bold brown and buff concentric bands and a broad flaring fan shape. Stereum hirsutum is coarsely hairy and yellow-orange beneath.

The bleeding species (S. gausapatum, S. rugosum) are excluded by the scratch test, since Silky Parchment produces no red droplets, and S. subtomentosum is excluded because it stains yellow. Trametes versicolor and Trichaptum biforme occupy the same branches but have poroid or toothed undersides rather than a smooth one. Small white Schizophyllum commune fans are also similar in size but have a split, gill-like fertile surface underneath.