Beech Mushroom Identification Guide

The First Impression

Late in the season, when most of the woodland fungi have already collapsed, you come across a bouquet of pale caps clustered on the trunk of a big broadleaf, often well above head height at the site of an old wound. The whole group grows from one point, the stipes curving outward and upward so the caps sit at different heights like a bunch of flowers. Caps are whitish to cream or pale tan, and the young ones carry a distinctive mottling: darker, water-soaked patches laid out in an irregular tiled or cracked-mosaic pattern, mostly across the centre. That tiling is where the scientific name comes from and it is the first thing to look for.

Where and When

This is a north temperate fungus of hardwood forest, and beech is the classic host, though elm, maple, willow, cottonwood and other broadleaves also carry it. It behaves as a weak parasite and then a saprotroph, entering through wounds in living but injured trees and continuing to decay the heartwood after the tree dies, producing a white rot. Because it works from within, fruit bodies emerge from cracks, broken limb scars and pruning wounds rather than from the bark surface generally, and they are frequently high on standing trunks, which means binoculars can be more useful than a knife. Fruiting runs from late summer well into late autumn, and it is notably tolerant of cold, often still appearing after the first frosts have finished off almost everything else.

Reading the Cap

Cap diameter runs from three to twelve centimetres, occasionally larger on a well-fed cluster. The shape starts convex with an inrolled margin and flattens out, sometimes becoming slightly depressed or a little wavy at the edge in age. The surface is smooth and dry, becoming faintly greasy when wet, and is never scaly, never hairy and never slimy.

Colour is pale: white, cream, buff or a light tan, usually darkest over the centre. The tiled mottling is strongest on young caps and consists of darker translucent blotches with slightly paler cracks between them, giving the effect of crazed glaze on pottery. On older or drier specimens the tiles fade and the surface may instead develop fine cracking, so treat the mottling as a strong young-specimen character. The margin is even, sometimes minutely fringed when young.

Gills, Stipe and Base

Turn a cap over. The gills are white to cream, close but not crowded, and their attachment is the crucial point: they are sinuate, meaning notched where they meet the stipe, or narrowly adnate, and at most they run a very short tooth down the stipe. They emphatically do not sweep broadly down the stipe the way an oyster fungus does. Edges are even and stay pale; there is no pinkish, brownish or greying discolouration except very late in decay.

The stipe is three to ten centimetres long and half a centimetre to two thick, whitish, dry, solid and fibrous-tough, often much tougher than the cap. It is central on isolated fruit bodies but frequently eccentric and strongly curved on crowded ones, because the stipes bend outward to give each cap light. There is no ring, no volva, no scaliness and no bulb. Follow the cluster down to its base: the stipes fuse into a common tough basal mass that is attached directly to wood. Cut into the wood there and you should find the pale rotted zone the fungus has created.

Flesh and Colour Change

Section a fruit body from cap centre to stipe base. The flesh is white, firm and thick, and it stays white. There is no latex, no blueing, no reddening and no gradual browning on exposure beyond the ordinary slow dulling of any cut tissue. The stipe flesh is noticeably more fibrous and tough than the cap flesh, and it may become hollow or pithy in old specimens. This lack of reaction is itself informative, since several superficially similar clustered wood fungi do change colour.

Taking a Spore Print

Cut a mature cap free just below the gills and set it gills-down on black card or dark glass, covered, for four to eight hours. The deposit is white and can be surprisingly heavy, so a good print is easy to obtain from this species. Against dark backing it shows clearly; on white paper you will need to angle the sheet to the light. Under the microscope the spores are almost spherical, roughly four to five micrometres across, smooth, thin-walled and unreactive in iodine. A pale lilac, pink, brown or rusty deposit would send you to another genus at once.

Separating the Look-alikes

Elm Oyster, Hypsizygus ulmarius. The closest relative and the main confusion. It is generally larger, grows singly or in small groups rather than in tight bouquets, usually lacks the tiled water-spot mottling, and is typically found on elm and box elder. Its spores are larger and more globose. Growth habit, host and cap mottling together settle it.

Oyster fungi, Pleurotus species. Gills run distinctly and broadly down onto a short lateral or strongly off-centre stipe, or the cap is attached almost directly to the wood. Caps are more shell- or fan-shaped and often grey to grey-brown, and the flesh is softer. Several also drop a faintly lilac-tinted print. The notched gill attachment of the Beech Mushroom is the clean separator.

Honey fungi, Armillaria species. Also clustered on wood, but they have a ring on the stipe, a finely scaly cap, gills that run down the stipe, and black bootlace rhizomorphs under the bark of the host. None of that occurs here.

Clustered Domecap, Lyophyllum decastes. Grows in tufts, but from soil and buried debris rather than from a wood attachment, and its caps are greyish-brown rather than pale and tiled.

Scalycaps, Pholiota species. Clustered on hardwood but with scaly, often slimy yellow-brown caps and a rusty-brown spore deposit.

Panellus and Sarcomyxa. Small, with a mere lateral stub of a stipe or none at all, and shelving rather than bouquet-forming.

Putting It Together

Tight clusters from a wound on hardwood, pale caps with tiled water-spot mottling when young, notched white gills, a tough whitish stipe with no ring, white unchanging flesh, a white spore deposit, and a late season. That set of characters is dependable across the range.