Silverleaf Fungus

Silverleaf Fungus is the single commonly encountered member of the genus Chondrostereum, now placed in the Cyphellaceae. It grows as an effused-reflexed fungus — that is, mostly a flat crust on the wood, but with the outer edge lifting away to form rows of small, wavy, overlapping brackets. The contrast between the white woolly upper surface and the smooth violet-purple fertile underside makes it one of the more attractive small crusts.

Its English name comes from the condition it induces in living trees of the rose family. Substances released by the fungus travel in the sap stream and cause the leaf cuticle to separate from the tissue beneath, so that the foliage reflects light and appears distinctly silvery. Affected branches often show the fruiting bodies later, on dying wood.

Fresh specimens are soft and slightly gelatinous, quite unlike the leathery Stereum crusts they superficially resemble; dried material becomes stiff and the purple colour fades to a dull buff-brown, which is a frequent source of confusion.

Fruiting body

Forms elongated patches along stumps, logs and cut surfaces, with the margin lifting into brackets typically 1–3 cm wide and only a few millimetres thick. Brackets are often fused laterally into long tiered rows, with wavy, lobed edges.

Upper surface

White to pale buff, densely hairy or felted, sometimes faintly concentrically zoned, and frequently discoloured green by algae on older material.

Fertile surface

Completely smooth — no pores, teeth or wrinkles — and coloured lilac, violet or rich purple-brown when fresh and moist. With age and drying it fades through dull vinaceous to pale brown, and the purple can be almost lost.

Flesh and spore print

Flesh is thin, soft and rubbery-gelatinous when fresh, drying hard and brittle; there is a narrow darker line visible in section under a lens. The spore print is white.

Grows on dead hardwood of many kinds and on wounded living trees: cut stumps, pruning scars, broken limbs and storm damage. It is particularly associated with members of the Rosaceae such as plum, cherry, apple, rowan and hawthorn, but is also very common on birch and willow.

Fruiting bodies can be found throughout the year and are most numerous and most strongly coloured in autumn and early winter. The species is widespread across the temperate Northern Hemisphere and has been carried to many other regions on planted stock.

Chondrostereum purpureum is both a white-rot saprotroph on dead wood and a wound parasite of living trees. Airborne spores land on freshly exposed sapwood — typically pruning cuts made in damp weather — germinate, and the mycelium spreads through the branch, breaking down lignin and cellulose and producing a pale, soft rot.

In the rose family the fungus provokes the characteristic silvering of foliage on infected limbs, and fruiting bodies commonly appear on those limbs once they die back. Spore release peaks in wet autumn and winter conditions, which is why orchard pruning is traditionally timed for dry summer weather when the wood seals quickly.

Stereum crusts are the usual confusion. Stereum hirsutum has a hairy upper surface too, but its fertile face is bright yellow-orange and never purple; Stereum rugosum forms a thicker, mostly flat pale crust whose surface reddens when scratched. Neither has the soft, slightly gelatinous fresh texture of Chondrostereum.

Trichaptum abietinum shows similar violet tones but has a distinctly poroid to toothed fertile surface and grows on conifers. Terana caerulea is a far more intense cobalt blue and is entirely flat, never forming brackets. Faded, dried Silverleaf Fungus is best confirmed by its thin wavy tiered brackets, white felted top and completely smooth underside.