Milk-white Brittlegill

Russula delica, the Milk-white Brittlegill, does not look like a typical member of its genus. Instead of a coloured cap on a slender stipe, it produces a heavy, chalk-white, funnel-shaped fruit body on a short stout stalk, and it typically begins developing below ground, erupting through the surface with soil, moss and leaf fragments still adhering to the cap.

The result is a mushroom that often looks dirty grey-brown from above even though the underlying flesh is pure white. Turning it over reveals the identity at once: thick, brittle, widely spaced gills that run down onto the stipe, and the granular flesh characteristic of the Russulaceae.

It sits close to Russula chloroides and to the white milkcaps of the genus Lactarius, with which it is frequently confused. The absence of any milky latex when the gills are cut immediately places it in Russula, since brittlegills never exude latex.

Cap

Large and heavy, 6-16 cm and occasionally to 20 cm across, at first convex with an inrolled margin, soon becoming deeply funnel-shaped. The surface is dry, matt and finely felted, chalk white when fresh but rapidly staining ochre, buff and rusty brown, and usually partly encrusted with soil, moss and litter picked up as the mushroom pushes upward.

Gills

White to cream, thick, brittle and moderately to widely spaced, and clearly decurrent — running well down the stipe. Gills of unequal length alternate. In many collections a faint blue-green tint appears where the gills meet the top of the stipe, and this zone is stronger in the closely related Russula chloroides.

Stipe

Short, thick and hard, 2-6 cm long and 2-4 cm thick, white and often browning where handled, tapering downwards. It is solid and firm rather than stuffed, with no ring or volva, and is frequently buried for much of its length.

Flesh & spore print

Flesh is white, thick, hard and granular, unchanging or slowly browning when cut. Critically, no latex is produced when the gills are cut, which separates the species from the superficially similar white milkcaps. The spore print is white to pale cream, and spores are broadly ellipsoid with warts joined into an incomplete network.

The Milk-white Brittlegill is mycorrhizal with a range of broadleaf and coniferous trees, especially oak, beech, hornbeam and pine, and grows on well-drained soils, often on chalk and limestone. It is a species of mature woodland, woodland banks, tracksides and thin-soiled slopes.

Fruit bodies develop underground and emerge from mid-summer through to late autumn, frequently appearing as cracked domes of lifted soil before the cap breaks the surface. The species is common and widespread through Europe, extending across temperate Asia, with a closely related complex of white species in North America.

This is an ectomycorrhizal fungus, forming sheathing associations with the fine roots of its host trees. The hyphal network it maintains in the surrounding soil delivers water, phosphorus and nitrogen to the tree in exchange for photosynthetic carbon, and can extend metres beyond the visible fruit bodies.

The habit of beginning development below the soil surface, common in this species, means the developing fruit body lifts and cracks the litter layer as it expands. This physically disturbs the soil surface and creates small openings colonised by mosses and invertebrates. The dense hard flesh decays slowly, so old blackened specimens can persist for weeks, hosting beetle larvae and secondary moulds.

The white milkcaps Lactarius vellereus and Lactarius piperatus are the closest confusions: both are white, funnel-shaped and stout, but they release a white latex from cut gills, which no brittlegill ever does. L. vellereus also has a densely velvety cap and much thicker gills; L. piperatus has extremely crowded, narrow gills.

Russula chloroides is very close indeed but has narrower, more crowded gills and a far more pronounced blue-green band where the gills meet the stipe. Lactarius controversus is another stout white species, but its gills are flushed pink and it too produces latex. Cutting a gill and watching for latex is the definitive separation.