Short-stemmed Russula

Russula brevipes is one of the largest and most substantial brittlegills of North American forests. The specific epithet means short-footed, and the stipe really is disproportionately stubby, so much so that mature specimens look like a broad white funnel sitting almost directly on the ground.

The species is famous for fruiting beneath the litter layer rather than above it. Developing fruiting bodies lift the duff into low mounds — often called mushrumps — and only break through the surface late, which is why so many collections are found smeared with soil and needles. This habit also means the cap is usually scuffed and discoloured rather than clean white.

It is also the most frequent host of Hypomyces lactifluorum, a parasitic ascomycete that coats the fruiting body in a bright orange, pimpled crust and distorts the gills into blunt ridges. That transformation is dramatic enough that the parasitised form is often mistaken for a separate species entirely.

Cap

The cap is large, commonly 7–20 cm across and occasionally more, convex with an inrolled margin at first, then broadly depressed and finally deeply funnel-shaped. The surface is dry, unpolished and matt, white to cream, and almost always marked with brown, buff or ochre stains from soil contact and handling. The cuticle is not sticky and does not peel readily.

Gills

Gills are the strongest character: narrow, very crowded, frequently forked near the stipe, and clearly decurrent, running down onto the stem. They are white to cream and often develop brownish stains where bruised. In the variety acrior the gills and the cap margin carry a distinct blue-green tint near the stipe.

Stipe

The stipe is short and thick — typically only 3–8 cm tall but 2–4 cm or more in diameter — solid, dry, white, and often browning where handled. It has no ring and no volva, and the base is blunt rather than bulbous or rooting.

Flesh & spore print

The flesh is thick, white, firm and brittle, slowly browning where cut or damaged, and produces no latex. The spore print is white to very pale cream. Under the microscope the spores are strongly warty with ridge connections.

Russula brevipes grows in conifer and mixed forest, associating with pines, firs, spruce, hemlock and Douglas-fir, and also occurring with oak in mixed western and eastern stands. It fruits scattered or in arcs and rings, often in deep needle duff where it pushes the litter into low humps before emerging.

It is common and widespread across North America, from the Pacific Northwest and the Rocky Mountains through the Great Lakes region to the eastern hardwood-conifer forests, and it is reported from parts of Mexico. Fruiting runs from summer into late autumn, later in coastal and montane areas, and it is often one of the bulkiest fungi present on the forest floor.

The species is ectomycorrhizal with a broad range of conifers and some hardwoods. Its hyphae sheathe fine roots and mediate the transfer of phosphorus, nitrogen and water to the host in exchange for photosynthate. Because it partners with many tree genera, it is present in a wide variety of forest types across the continent.

Its most conspicuous ecological relationship, though, is as a host. Hypomyces lactifluorum, an ascomycete parasite, colonises the developing fruiting body and replaces its surface with a dense orange crust of perithecia, arresting gill development into low blunt folds and firming the flesh. Parasitised specimens keep the funnel shape and short stipe of the host but are unmistakable in colour. Other Hypomyces species and various moulds also colonise old specimens, and the persistent flesh supports beetle larvae and small mammals that scatter spores.

Lactarius piperatus, Lactarius deceptivus and Lactifluus vellereus are all large white funnel-shaped fungi of similar build, but every one of them beads white latex from cut gills within seconds; Russula brevipes never does. L. deceptivus additionally has a cottony roll of tissue along the young cap margin, and L. vellereus has a velvety cap and much more widely spaced gills.

Russula cascadensis is a smaller white western species with a more strongly inrolled margin and less decurrent gills. Leucopaxillus albissimus is also large and pale but has tough, fibrous, non-brittle flesh that tears rather than snaps, a thick white mycelial mat binding the litter at its base, and gills that separate cleanly from the cap.