Hebeloma sacchariolens Identification Guide

The First Impression

The smell arrives before the mushroom. Walking through damp birch scrub, a willow carr, a mossy dune slack or a wet woodland margin in autumn, you catch something intensely sweet and slightly cloying on the air, closer to scented soap, burnt sugar or orange blossom than to anything else on a woodland floor. Track it down and you find a small troop of pale, plain mushrooms in the moss and leaf litter: buff to cream caps, low domed, faintly greasy, on whitish stems with no ring.

Without the smell they would look like any number of unremarkable brown-spored agarics. With it, you are already in a very small group. That sweet scent is by far the most useful character in the species and the fastest way to place a collection, and it is worth training your nose on because the sensation is memorable and quite unlike the radish smell of most Hebeloma species.

Reading the Cap

Caps measure 2 to 5 cm across, occasionally up to 7 on rich damp ground. They are hemispherical then convex, opening to broadly convex or flat, generally with a low blunt umbo and often with a slightly wavy or uplifted margin in age.

The surface is smooth and bald, greasy to slightly viscid in wet weather and matt when dry. Colour is pale and rather characterless: cream, pale buff, ochre-tan or dull clay, usually a little warmer and darker at the disc and paler toward the margin, but without the sharp two-toned pattern of Hebeloma mesophaeum. Some collections have a faint pinkish or fawn cast. In dry spells the cap bleaches nearly to ivory.

The margin is inrolled when young and may carry faint pale flecks of a very thin, evanescent veil, but there is no persistent hanging fringe, no cortina and no fibrillose girdle left on the stipe. If your specimen has a clear veil zone banding the stipe, look elsewhere in the genus.

Gills, Stipe and Flesh

Gills are crowded and narrow to moderately broad, adnate or shallowly notched, sometimes appearing nearly free in flattened old caps. They run pale grey-buff or clay when young to a dull warm snuff-brown at maturity, with no purple or rust component in the colour.

Examine the edges with a lens. They are whitish and minutely fringed, and in humid weather young specimens weep small colourless droplets, which dry to leave scattered brown flecks. The weeping here is generally less profuse than in Hebeloma crustuliniforme, so treat it as supporting evidence rather than a decider.

The stipe is 3 to 8 cm long and 4 to 10 mm thick, whitish to pale cream, cylindrical or slightly swollen and sometimes a little club-shaped at the base. It is finely mealy or pruinose over the upper third, silky-fibrillose lower down, and it often discolours brownish from the base upward with age. It is stuffed and becomes hollow, snapping cleanly rather than shredding into long fibres. There is no ring, no membranous structure of any kind, and no volva. The base sits in white mycelium binding moss, sand or litter, without any long rooting extension.

Cut a fruitbody in half. The flesh is white to pale buff, becoming brownish in the stipe base, and it does not change colour on exposure. The scent is much stronger in the cut flesh, so slice and sniff immediately if you are hesitating. Some describe it as marzipan overlaid with soap or a perfume note; the key point is that it is sweet, not vegetable-sharp.

Taking and Reading a Spore Print

Lay two or three mature caps gills-down on white paper under a cover for three to six hours. The deposit is dull clay-brown to snuff-brown, warm and matt, the same colour family as every other Hebeloma. That immediately excludes rusty-printed Cortinarius, purple-brown printed Psathyrella relatives and white-printed genera.

The microscopy is where this species becomes decisive, because the spores are unusually large for the genus. They measure roughly 11 to 15 micrometres long by 6.5 to 8.5 wide, sometimes larger, and are amygdaliform to slightly lemon-shaped with a drawn-out apex. The walls are strongly and visibly warted or verrucose, coarser than in most of its relatives, and the spores turn distinctly reddish in Melzer's reagent. If you have even a basic microscope, measuring twenty spores will separate this species from the smaller-spored pale Hebeloma species faster than anything else.

Be aware that modern work has split the sweet-smelling Hebeloma species into several closely related taxa, distinguished mainly on spore dimensions, cystidial shape and habitat. Naming a collection to the aggregate on scent, pale colours and large warted spores is a perfectly defensible field conclusion.

Substrate, Season and Ecology

This is an ectomycorrhizal fungus and it needs a host tree. Birch and willow are the commonest partners, with alder, poplar, hazel, beech and occasionally conifers also recorded. The ground is characteristically damp: wet woodland edges, mossy flushes, carr, ditch banks, the moist hollows between dunes where creeping willow grows, and heathy ground with scattered birch.

Fruiting runs from late summer through autumn, peaking in the wettest weeks, and fruitbodies come up scattered or in small loose groups rather than in the dense arcs typical of some relatives. Because it is mycorrhizal, its presence marks living tree roots even where the trees themselves are low scrub, which is why dune slacks with knee-high creeping willow can be surprisingly productive.

Separating It From Look-alikes

Start with the smell, then confirm with structure and spore size.

Hebeloma crustuliniforme is larger and firmer, smells sharply of radish rather than sweet, has more conspicuously weeping gill edges, and has distinctly smaller spores at around 9 to 13 by 5.5 to 7 micrometres. It also favours drier, disturbed path-edge ground.

Hebeloma mesophaeum has a sharply two-toned cap with a dark disc, carries a fibrillose veil that leaves a brown-dusted girdle on the stipe, smells weakly of radish, and has small spores around 8 to 11 micrometres.

Hebeloma radicosum smells sweetly of almond, which can cause momentary confusion, but it is far larger, has a scaly cap, a proper membranous ring and a long tapering root; nothing about its structure resembles this species.

Hebeloma sinapizans is much bigger, smells of radish, and has a hollow stipe containing a hanging plug of tissue.

Other sweet-smelling members of the sacchariolens group differ only in fine microscopic detail, and separating them in the field is not realistic.

Outside the genus, Inocybe species can smell strongly but are typically spermatic or earthy rather than sweet, and their caps are dry, radially fibrillose and often umbonate with a splitting margin. Cortinarius species have a cobwebby cortina and rusty prints. Agrocybe species have firmer, more ochre caps and often a ring. Any pale mushroom with a white spore print is out on the print alone.

Field Checklist

Powerful sweet scent of burnt sugar, scented soap or orange blossom, strongest in cut flesh; pale cream to buff smooth greasy cap with no sharp dark disc; crowded gills maturing snuff-brown, edges whitish and faintly weeping; whitish ringless stipe, pruinose above, browning from the base; unchanging pale flesh; clay-brown spore print with large, coarsely warted almond-shaped spores; damp ground with birch or willow, late summer to autumn.