Glue Crust

Glue Crust earns its name from a remarkable behaviour. Where a colonised dead branch touches a neighbouring living branch, the fungus produces a hard adhesive pad across the contact point, bonding the two together. The dead branch is then held aloft instead of falling, and the fungus keeps it to itself.

In appearance the fruiting body is undramatic: a thin, closely attached crust in muted grey-lilac, buff or brown tones, its surface finely cracked into a mosaic on older parts. The genus Hymenochaete (Hymenochaetaceae) is characterised microscopically by brown, thick-walled pointed setae in the fertile layer, which give the surface a slightly velvety look under a lens.

The species is a classic of hazel coppice and damp hedgerow, and once a searcher learns to look for suspended dead sticks with pale cemented joints, it turns up regularly.

Fruiting body

Resupinate, thin and closely appressed, spreading in irregular patches that merge along the branch. Thickness is well under a millimetre.

Surface

Pale grey-lilac to buff or greyish-brown, matte and finely velvety under a lens; older central areas crack into small irregular plates, exposing paler tissue in the fissures.

Margin

Thin, paler and indistinct, fading out onto the bark without a raised or fringed edge.

Glue pads and texture

At points where the colonised branch touches another, the crust thickens into a hard, pale, cement-like pad that firmly bonds the two. The fruiting body is hard and brittle when dry, slightly pliable when damp. Spore print white.

Overwhelmingly associated with hazel (Corylus avellana), especially in coppice, damp woodland and old hedgerows; it also occurs on willow, oak, ash and other broadleaves. It fruits on dead attached branches and on the suspended sticks it has glued into place.

Fruiting bodies are perennial in effect and can be found in any month, being easiest to detect in winter when hazel is leafless and hanging dead branches are obvious. The species is widespread in Europe and temperate regions generally.

Hymenochaete corrugata is principally a saprotroph causing a white rot, though it also behaves as a weak parasite, moving into stressed or dying branches on living hazel. Its distinctive strategy is territorial: by gluing dead branches into the canopy, it keeps its wood out of contact with the soil and away from the vigorous fungi and invertebrates of the litter layer.

This suspension also keeps the colonised branch drier and better ventilated, conditions that suit the fungus while excluding many competitors. Spores are released from the exposed crust and colonise fresh dieback elsewhere in the hazel stand.

Hymenochaete rubiginosa shares the family's velvety brown fertile surface but is a much richer rust-brown, forms tiered reflexed brackets, and grows on oak stumps rather than hazel branches.

Peniophora quercina is lilac but waxy and curls off the bark in flakes with a black under-surface. Vuilleminia comedens is glassy and develops beneath bark, rolling it back. None of these produce the hard cement pads at branch contact points, which are the decisive character for Glue Crust.