Silverleaf Fungus Identification Guide

The first impression

You generally meet Silverleaf Fungus on a stump or a fallen limb rather than on the ground. The typical scene is a cut plum or cherry stump in an old orchard, a wind-thrown birch, a coppiced willow, or a poplar branch lying in wet ground. What you see is a tier of small, wavy, shelf-like brackets running along the wood, each two to four centimetres deep, with the individual shelves often fusing sideways into a continuous frilled band. The top surface is dull, greyish and obviously hairy; the free edge is often paler or white when the fungus is growing. Then you crouch, tilt your head and look at the underside, and there is the character that names the species: a smooth, even, lilac to purple-violet surface with no pores, no gills and no teeth at all. Fresh, damp material is startlingly purple; that colour is the reason this fungus rewards a second look at every unremarkable grey crust you pass.

Growth form: effused-reflexed

Before measuring anything, work out the growth form, because it is half the identification. Chondrostereum is effused-reflexed, meaning that part of the fruit body lies flat on the wood like a crust and part of it curls outward into a bracket. On the underside of a horizontal log it may be almost entirely resupinate, a purple sheet pressed to the timber. On a vertical stump face it usually forms proper shelves. The brackets are thin, one to three millimetres thick, with wavy, lobed and often overlapping margins, and they merge laterally into rows sometimes half a metre long. There is no stipe and no attachment point beyond a broad lateral join to the wood.

Reading the upper surface

Run a thumb across the top. It is finely tomentose to shaggily hairy, matt, and grades from white at the actively growing margin through buff and ochre to grey-brown behind. Older shelves accumulate green algae and look mossy, which disguises them completely, so any grey furry bracket on broadleaf wood deserves a look underneath. There is no zonation into sharply contrasting concentric bands of colour, though faint growth ridges are usually visible.

Reading the spore-bearing surface

This is the diagnostic surface. It is smooth, sometimes very slightly wrinkled or bumpy where it follows the contours of the bark, and it produces spores over its whole area rather than inside tubes. Colour when fresh and moist ranges from bright lilac and violet through purplish-brown to a deep vinaceous. As the fruit body dries and ages, the purple leaches away to a dull buff, tan or greyish, so old material can be very hard to name; wetting a corner with a drop of water often revives enough colour to see. Under a lens the surface has no visible structure whatsoever, which is the key negative character.

Texture, section and colour change

Pick a shelf off and squeeze it. Fresh material is soft, flexible and distinctly rubbery-gelatinous, closer to leather softened in water than to the hard corkiness of a true polypore, and it shrivels to a brittle wafer when dry, then revives when wet again. Cut a bracket in cross section with a sharp blade and hold it up to the light: you should see a thin dark line running through the middle. This is a gelatinous layer sandwiched between the hairy upper tissue and the hymenium, and it is the structural feature that gives the genus its name. Cutting produces no milky fluid, no red bleeding and no rapid colour change; the cut face simply darkens slowly as it dries.

Spore print

Crusts and brackets can be printed just like a gilled mushroom, though it takes patience. Cut a piece with its hymenium facing down, prop it on matchsticks over white paper or a glass slide, cover it, and leave it overnight in a humid, still place. The deposit is white to very pale cream, which is worth confirming because a white print rules out several of the brown-spored crust and bracket groups. Fruiting bodies release spores mainly in cool, damp weather.

Substrate, season and ecology

Silverleaf Fungus is a wood decayer of broadleaf trees, and it also colonises living tissue through wounds. Its favoured hosts are members of the rose family, especially plum, cherry, apple, hawthorn and rowan, but it is common on birch, willow, poplar, alder, beech and many others, and it is very frequent on freshly cut stumps and pruning wounds. Its mycelium in the trunk releases compounds that travel to the foliage and separate the leaf surface layer, so that infected trees show a distinctive silvery sheen on their leaves; that silvering on a plum or cherry in summer is a strong hint that brackets will appear on the trunk or on the stump later. Fruit bodies can be found year-round but are at their best from late summer through winter, and they persist in a dried state for months.

Separating it from look-alikes on morphology alone

The closest lookalikes are the Stereum crusts, which share the effused-reflexed habit and the smooth hymenium. Hairy Curtain Crust, Stereum hirsutum, has a bright yellow to orange-buff underside and a much tougher, drier, non-gelatinous texture that cannot be squashed. Stereum rugosum and Stereum gausapatum are pale buff to greyish underneath and release a red juice when the fresh hymenium is scratched; Chondrostereum never bleeds. Stereum sanguinolentum, on conifers, also bleeds red. None of the Stereums show the dark gelatinous line in section.

Cobalt Crust, Terana caerulea, is a striking blue-violet but is entirely resupinate, forms no brackets, and has a waxy, cushioned, minutely bumpy surface. Trichaptum abietinum has a violet edge but a poroid to toothed underside and grows on conifers. Purple Jellydisc, Ascocoryne sarcoides, is a gelatinous blob or disc rather than a bracket, growing in clusters on beech and other hardwood. Wrinkled Crust, Phlebia radiata, is orange to pinkish with strong radiating folds. Byssomerulius corium is cream to buff with a merulioid, shallowly wrinkled surface. Finally, any specimen with visible pores under a lens is a polypore, not this species: the completely smooth, poreless, purple hymenium plus the hairy grey top plus the rubbery section is the combination that only Chondrostereum offers.