Flame Mycena Identification Guide

Where you find it and what you see first

Flame Mycena is a mountain species of conifer duff. The setting is a fir, spruce or pine forest at moderate to high elevation, with a deep, springy layer of fallen needles under the trees and very little green at ground level. In the western ranges it often appears within a few metres of a retreating snowbank in early summer, and again more widely after the first serious autumn rains; in boreal forest it comes with the late summer wet.

You almost always see the colour before the shape. A brilliant scarlet spark against a floor of dull brown needles is visible from several paces, and once you have found one, dropping to a crouch usually reveals a scattered troop of a dozen or more within a couple of square metres. The fruit bodies are tiny and set close to the litter, so the useful search posture is low and slow.

Reading the cap

The cap is 0.5 to 2.5 cm across, conical or bell-shaped at first, expanding to broadly convex, often with a small blunt umbo at the centre. It is at its most vivid when young: scarlet to orange-red over the disc, grading through orange to yellow-orange at the margin, so a fresh cap looks like a small ember with a bright rim.

The surface is moist and thin enough to be translucent-striate, meaning the lines of the gills beneath show through as radial streaks running in from the margin. Hold a cap up to the light to check this. Colour fades markedly with age, weather and sun, so a well-worn cap may be little more than pale orange-yellow and can no longer be identified on colour alone. In very young specimens the extreme margin is minutely fringed with fine pale fibrils.

Gills, stipe and the two key characters

Turn the cap over and get a hand lens onto the gill edge, because the first key character lives there. The gills are adnate, usually with a short tooth running a little way down the stipe, subdistant to close, with perhaps fifteen to twenty-five full-length blades reaching the stem and shorter ones interleaved. The gill faces are pale yellow to orange-yellow. The gill edges, however, are a bright orange-red, distinctly darker and more saturated than the faces, giving a marginate line that is obvious under magnification and often visible to a sharp naked eye.

The second key character is at the other end. The stipe is 2 to 7 cm long and only 1 to 2.5 mm thick, equal, hollow, brittle and slightly cartilaginous, smooth and yellow-orange toward the top and more orange to reddish below. At the very base it is clothed in a conspicuous tuft of stiff, bright orange-red hairs that bind the surrounding needles into a small ball. Do not snap the mushroom off; ease it out of the duff with your fingers so the basal fibrils come away intact, because a specimen without its base has lost half its identity.

The flesh is essentially negligible, thin, watery and coloured like the surface. There is no latex, no ring, no volva, and no meaningful colour change on cutting beyond the fading that comes with drying.

Taking a spore print

Small caps dry out before they finish dropping spores, so a print needs a little help. Set two or three of the largest, most fully expanded caps gill-side down on black paper or a black plastic lid, add a single drop of water to the paper beside them, and cover the lot with an upturned cup or a clear plastic tub to hold humidity. Leave it four to eight hours or overnight.

The deposit is white and often sparse. Under the microscope the spores are smooth, ellipsoid, roughly 7 to 9 by 4 to 5 micrometres, and amyloid, turning blue-grey in Melzer's reagent, which is a hallmark of the genus. The gill edge is lined with club-shaped cystidia filled with orange pigment, and those cells are the physical explanation for the coloured edge you saw with the lens.

Substrate, season and range

Flame Mycena is a litter decomposer. It works on fallen conifer needles and fine woody fragments in the duff layer, never on standing wood, never in grassland, and only incidentally in moss. That habitat restriction is genuinely diagnostic: a bright red mycenoid mushroom on a log or a lawn is something else.

Its range covers the montane and subalpine conifer forests of western North America from California north through the Cascades and Rockies into Alaska, and it extends through boreal forest. It fruits from early summer near melting snow at high elevation through to late autumn at lower elevations, scattered to gregarious, usually in the shadier and damper pockets of the forest floor.

Separating it from its look-alikes

Atheniella aurantiidisca is the commonest confusion in the same western conifer duff. Its cap is bright orange, but its gills are white to pale cream with no coloured edge, and its stipe is pale and its base white, with no tuft of orange fibrils.

Atheniella adonis is coral to pinkish-red rather than scarlet-orange, its gills are whitish to faintly pink without a marginate edge, and the stipe base is white and smooth. It also leans toward mossy and damp litter habitats rather than deep conifer duff.

Mycena acicula is smaller still, with an orange-red cap and a yellow stipe, but its gills are pale yellow with yellow rather than red edges, it grows on small fallen twigs and woody debris in damp broadleaved settings, and its spores are not amyloid.

Mycena aurantiomarginata has exactly the same structural plan, with vivid orange gill edges and an orange-fibrillose stipe base, but its cap is a dull olive-brown to brownish-orange rather than scarlet, so the two separate on cap colour alone.

Waxcaps such as Hygrocybe miniata can match the colour but the resemblance ends there: their gills are thick, waxy and widely spaced, their flesh is soft and waxy rather than thin and brittle, their stipes are stouter and not cartilaginous, and they belong to grassland, moss and open ground.

Xeromphalina species are orange-brown rather than scarlet, with decurrent gills and a tough, wiry, dark stipe, and they grow in mats on wood or on compacted conifer litter.

Field checklist

Scarlet fading to orange-yellow at the margin; translucent-striate cap; pale yellow gills with bright orange-red edges; slender hollow yellow-orange stipe; a tuft of stiff orange-red hairs at the base binding needles; white amyloid spore print; conifer duff at elevation.