Bleeding Broadleaf Crust Identification Guide

The First Encounter

Crust fungi are the group most people skip, and Bleeding Broadleaf Crust is the ideal one to start with because it carries a test that gives an unambiguous answer in ten seconds. You will typically meet it in damp broadleaf scrub or woodland, on a dead but still standing hazel stem, an alder branch over a stream, or a fallen birch limb. It appears as a smooth to slightly lumpy pale crust plastered flat against the wood, often running for 10-30 cm along a branch, sometimes wrapping right around a thin stem. The overall look is of a thick coat of pale grey-buff paint that has partly dried and cracked.

The Scratch Test

Do this first, because everything else is supporting evidence. Take a fingernail, a twig tip or the back of a knife and draw it firmly across the fertile surface of a fresh, damp specimen. Within seconds a red to blood-red juice appears along the scratch, sometimes gathering into small droplets and eventually drying to a dark reddish-brown stain. The reaction is bright and unmistakable when the fungus is moist and active.

Two practicalities. First, it only works on fresh, well-hydrated material; a sun-dried or frost-hardened crust in midwinter may not react at all, so wet it and wait, or return after rain. Second, the scratch stains the surface permanently, which is actually helpful, because an old crust showing dark reddish scratch marks is evidence that someone or something has already tested it.

Reading the Fruit Body

Bleeding Broadleaf Crust is essentially resupinate, meaning it lies flat on the substrate with the fertile surface facing outwards. It differs from many crusts in being distinctly thick, often a millimetre or more, and hard rather than papery. Run a thumbnail under the edge: the margin is usually a narrow, paler, slightly raised whitish or cream rim that may lift a little from the wood, while the older central part is firmly welded on.

The fertile surface itself is smooth to gently uneven or slightly warted, without pores, teeth or gills of any kind. Colour ranges from pale cream and buff through greyish-ochre to a dull yellowish tan, often with faint concentric shading. On thin branches the crust may develop a narrow reflexed lip along the upper edge, forming a rudimentary shelf a few millimetres wide, but it never builds the tiered fan-shaped brackets of some relatives. As the crust ages and dries, it commonly cracks into an irregular mosaic, revealing the paler wood in the fissures.

Texture and Section

The consistency is tough, hard and leathery, closer to dried varnish than to flesh. Cut a fragment away with a knife and examine the cut edge with a lens: you should see a thin, dense, pale layer built directly onto the wood, with no distinct gelatinous zone and no soft context. It is not gelatinous when wet, and it does not swell noticeably in the way jelly fungi do, though it becomes slightly more pliable and much more willing to bleed.

Spore Print and Microscopy

Getting a print from a crust is possible but fiddly. Cut a small slab of wood carrying a patch of the crust, prop it fertile-side down over dark card with a couple of matchsticks to hold it clear of the surface, cover the arrangement to keep the humidity up and leave it overnight. A productive specimen drops a white deposit. Under the microscope, the spores are narrowly cylindrical and slightly curved, and they turn blue-grey in iodine, an amyloid reaction. The bleeding itself comes from specialised conducting hyphae running through the fertile layer, which is a nice detail to know but not something you need to see to make the identification.

Substrate, Host and Season

This is a wood decayer of dead broadleaved material, and the host list is a useful part of the identification. Hazel is the classic substrate, with alder, birch, oak, beech and willow all regular. It particularly favours standing dead stems, attached dead branches and recently fallen wood rather than soft, deeply rotted logs, and it is a common colonist of neglected hazel coppice, scrubby woodland edges and streamside alder.

The crust is effectively perennial and can be found in any month of the year, which makes it a good winter subject. Spore production peaks in damp conditions, and the bleeding reaction is strongest in mild, wet weather from autumn through spring. It also grows readily on the cut ends and pruning wounds of living broadleaves.

Separating the Look-Alikes on Morphology Alone

Within the genus, sort first by substrate and then by growth form.

Stereum sanguinolentum also bleeds red, but it grows on conifer wood, chiefly spruce and pine, and is a thinner, more flexible fungus that turns up its edge into narrow wavy shelves with a hairy, greyish-brown upper surface. Broadleaf host plus thick, hard, largely flat crust means Bleeding Broadleaf Crust.

Stereum gausapatum, the bleeding oak crust, is the trickiest neighbour. It bleeds too, but it is thinner, more strongly bracket-forming with overlapping wavy tiered caps, has a distinctly hairy or velvety upper surface on those reflexed parts, and shows a more orange-brown to reddish-tan fertile surface. It is strongly tied to oak.

Stereum hirsutum does not bleed at all. It forms conspicuous, hairy, concentrically zoned brackets in bright yellow and orange tones with wavy margins, and it is far more three-dimensional than a flat crust.

Stereum subtomentosum likewise does not bleed, is more fan-shaped and velvety with an olive tone, and often bruises yellowish where damaged.

Outside the genus, Chondrostereum purpureum forms a similarly flat to slightly reflexed crust but is lilac to purplish on the fertile surface, softer in texture, and does not release red juice. Peniophora species are smoothly resupinate but tend to be pinkish, orange-pink or violet-tinged, are thinner and often have a distinctly gelatinous feel when wet, and never bleed. Cylindrobasidium laeve is a soft cream crust with a fringed margin and no bleeding reaction. Vuilleminia comedens grows under the bark of dead oak twigs and pushes the bark back in strips, showing a glassy pale grey surface, and again does not bleed.

Summary Routine

Damp broadleaf deadwood, especially hazel or alder; a thick, hard, cream to greyish-buff crust with a narrow paler rim, smooth to slightly warted and often cracked; no pores, teeth or gills; a fingernail scratch that releases red juice within seconds; white spore print. Two of those characters together, bleeding plus broadleaf host, will get you to this species more often than not, and the thick flat growth form closes out the remaining alternatives.