Short-stemmed Russula Identification Guide

The first impression

Often you find this species before it has properly appeared. Walking a North American conifer forest in late summer or autumn, you notice a low dome in the needle duff, a cracked mound of litter pushed up from below, and scraping the surface reveals a hard white cap shouldering its way out of the soil. Fully emerged fruit bodies are unmistakable in build: broad, chalk-white, shallowly funnel-shaped caps sitting almost on the ground on a stalk so short and thick that the whole fungus looks squashed. The white is rarely clean - most caps are streaked and blotched with ochre, tan and rust where debris has stuck and where the surface has aged - and everything about the fruit body feels hard, dense and heavy for its size.

Reading the cap

The cap runs 7-20 cm across and can exceed 25 cm in old, well-fed specimens. It starts convex with a tightly inrolled margin, then flattens and develops a broad central depression, ending broadly funnel-shaped. The surface is dry, matte and unpolished, with a texture closer to chalk or kid leather than to the shiny cuticles of most brittlegills, and it is frequently pitted with adhering needles, soil and moss. Fresh growth is white; as the fruit body ages it discolours in patches to buff, ochre, cinnamon and finally rusty brown, usually starting where it has been bruised or where the duff has pressed against it. The cuticle does not peel away in a clean sheet - it tears in small flakes at the very margin at best. The margin itself stays inrolled a long time and is never grooved or lined.

The gills

Turn the cap over and read the gills carefully, because they carry two useful characters. They are close to crowded, narrow, and clearly subdecurrent, running a short way down onto the stalk rather than stopping cleanly at it. They fork irregularly, particularly near the stalk, and short intermediate gills are interspersed. Colour begins white to cream, dulling to pale buff, and old or handled gills stain slowly brownish. In some collections there is a distinct blue-green or greyish-green flush right at the junction of gills and stalk apex, a subtle but very helpful character when it is present. Draw a fingernail across the gills: they break in brittle fragments rather than bending, which is the single fastest genus test.

Stalk, base and flesh

The stipe gives the species its name. It is short - 2-6 cm, sometimes barely 2 cm on a 15 cm cap - and very thick, 2-4 cm across, cylindric or tapering downward, and rock-hard when fresh. It is white and dry, with a slightly rough or chalky surface, and it discolours brown where handled and around insect tunnels. There is no ring, no veil and no sac at the base, just white mycelium binding soil and needles. Cut the fruit body vertically. The flesh is very thick, white and dense, and it snaps like a piece of chalk instead of tearing in fibres, because it is built partly of rounded cells rather than long hyphae. On exposure it stains slowly to brownish or rusty over tens of minutes. Crucially, no latex appears anywhere - press cut gills against a dark surface and nothing milky beads out. The odour is faint, sometimes slightly fishy or oily in age.

Getting a spore print

Because the stalk is so short, cut the cap free with a knife and set it gills-down on paper that is at least partly black, covering it to keep humidity in. A mature cap deposits heavily overnight. The print is white to cream, at the pale end of the brittlegill range. Under a microscope the spores are broadly ellipsoid, ornamented with warts joined here and there by fine connecting lines into a partial net, and the ornamentation blackens in Melzer's reagent. That amyloid ornamentation with a white to cream print is characteristic of the group.

Substrate and season

This is a root-partner fungus, not a decomposer. It forms sheathing associations with conifers above all - fir, spruce, hemlock, Douglas fir and pines - and also with hardwoods in mixed stands across much of North America. It fruits from soil under the litter layer, usually solitary or in scattered groups, sometimes in loose arcs, and its habit of maturing beneath the duff means finds are often half-buried and heavily soiled. The season runs from summer into late autumn, extending into winter in mild coastal forest. Old fruit bodies persist for weeks, blackening slowly as they decay.

An ecological detail worth knowing

This species is the principal host of the parasitic ascomycete Hypomyces lactifluorum, a fungus that colonises the developing fruit body, wraps it in a bright orange to red pimpled crust and completely obliterates the gills, leaving smooth, blunt ridges. Finding those orange-crusted, gill-less deformities in a conifer stand is indirect evidence that the Short-stemmed Russula is present, even when uninfected fruit bodies are not showing.

Separating the look-alikes

Lactifluus piperatus, Lactarius deceptivus and Lactifluus subvellereus are the serious confusions: all are large, white, crowded-gilled forest mushrooms with brittle flesh. The test is latex. Cut fresh gills and watch for thirty seconds; the milkcaps bead white latex, this species produces none. Lactarius deceptivus additionally has a cottony, rolled, overhanging margin and a browning, scurfy stalk.

Russula cascadensis and other small white brittlegills of the same forests are much smaller overall, with proportionally longer stalks and gills that stay whiter.

Leucopaxillus species mimic the size and colour but their flesh is pliant and fibrous rather than chalky - it bends and tears instead of snapping - and they usually sit on a conspicuous mat of white mycelium binding the litter.

Large white Clitocybe and Tricholoma species also have fibrous, flexible flesh, and their gills bend rather than shatter.

White Hygrophorus species have thick, waxy, widely spaced gills and a soapy feel, quite unlike the crowded narrow gills here.

Field checklist

Large white matte funnel-shaped cap staining ochre-brown; crowded narrow subdecurrent forking gills, sometimes green-flushed at the stalk apex; very short, thick, hard white stalk; chalky brittle flesh; no latex; white to cream spore print; from soil under conifers. That combination is Russula brevipes.