Stubble Rosegill Identification Guide

The First Impression

This is a mushroom of open, worked ground rather than woodland. You are walking the edge of a field after the crop has been cut, or past a heap of spent compost behind a nursery, or along a wood chip mulched border in a park, in the weeks after the first substantial autumn rains. What you see is large and pale: a soft, bulky mushroom 10 to 20 cm tall with a smooth greyish white cap that catches the light with a wet sheen, standing singly or in loose scattered groups directly out of bare soil, straw litter or chip. Nothing about the setting suggests trees, and that is a genuine clue rather than an anomaly. Approach and check the base, because the identification hinges on a white bag around the bottom of the stem.

Reading the Cap

Caps are 5 to 15 cm across and occasionally reach 20 cm on rich substrate. Young ones are egg shaped, then become bell shaped, then broadly convex, and finally almost flat with a low umbo, with the margin thinning, often becoming wavy, and sometimes showing faint striations in age. The colour is white, pale grey, mouse grey or greyish brown, generally darkest over the centre and often paling toward the edge, and there is considerable variation between collections. The single most useful surface character is that the cap is markedly viscid or slimy when moist, so that leaves, chaff and grit stick to it; when it dries the surface goes silky, shining and slightly streaky. Draw a finger across a fresh cap and the tackiness is obvious.

The Gills

The gills are free, ending in a clear channel around the top of the stem, and they are crowded, broad and ventricose, bulging in the middle and narrowing at both ends. Follow the colour sequence, because it is diagnostic: pure white in buttons, then a clean salmon pink as the spores mature, and finally a duller pinkish brown in old fruit bodies. The edges are finely fringed and slightly paler than the faces. Halve a fruit body vertically to confirm that the gills genuinely stop short of the stem rather than merely appearing to.

The Stem

The stem is 5 to 15 cm long and 1 to 2 cm thick, solid, and tapering upward from a swollen base, which gives it a slightly club like profile. It is white to pale cream, smooth or finely silky fibrillose, and sometimes minutely downy near the bottom. Once again the negatives carry weight: there is no ring, no ring zone and no set of veil girdles anywhere on the stem. Check the whole length in good light before deciding.

Base and Volva

The base sits inside a loose, membranous, sac like volva, white to pale greyish and often stained brownish by soil, with two to four irregular lobes around the free rim. It is thinner and more fragile than the sac of some relatives and tears easily, so it is frequently left behind in the ground when a fruit body is pulled. Always dig: cut a ring in the soil several centimetres out from the stem and lift the whole thing so the volva comes up intact. A free, sac like volva together with a ringless stem and free gills defines the group this species belongs to.

Flesh and Odour

Cut a fruit body from top to bottom. The flesh is white, soft and watery, thick over the cap centre and thin at the margin, and it does not change colour appreciably on exposure, though the very base of the stem may go faintly brownish after a long time. The section is also the best way to see that the volva is a separate sheath around the stem rather than a swelling of it. The odour is mild and faintly earthy.

Taking a Spore Print

This species prints heavily and quickly, so it is an easy confirmation. Cut a mature cap free, lay it gill side down on white paper, cover it with a bowl, and leave it two to four hours. The deposit is a strong pinkish brown to salmon, sometimes with a deeper brown cast when very thick. Under the microscope the spores are the clincher for the genus and separate it from its nearest relatives: broadly ellipsoid, smooth, thick walled and large, roughly 11 to 18 by 7 to 11 micrometres, distinctly bigger than those of the related species that share the same body plan.

Substrate and Season

Volvopluteus gloiocephalus is a saprotroph of nutrient rich, disturbed ground. Its classic habitat is arable land: stubble fields and ploughed ground where straw and root residues are breaking down. It is equally at home on compost heaps, manure enriched soil, hay and silage residues, wood chip mulch, garden borders, landfill capping, roadside spoil and lawns laid over buried compost. Because it forms no root partnership, a fruit body standing in the middle of an open field is entirely normal. The season runs from late summer to late autumn, with the heaviest fruiting after the first prolonged autumn rains, and fruit bodies appear singly, scattered, or occasionally in loose troops and arcs along a spread of compost. Growth is fast and the soft flesh collapses quickly, so fresh material is worth examining on the spot.

Separating It from Look-alikes

• Volvariella volvacea has a dry, silky cap marked with dark radiating streaks and a thick, firm, dark grey brown volva, and it is a warm climate species of straw and plant waste. Its spores are noticeably smaller.
• Volvariella bombycina fruits on standing or fallen broadleaved wood and has a cap covered in long silky white to yellowish fibres, with a large pale volva.
• Pluteus cervinus and its relatives share free gills and a pink print but have no volva at all, have dry fibrillose brown caps, and grow on wood, sawdust and buried timber.
• Amanita species also combine free gills with a volva, but their gills remain white at maturity, they drop a white spore print, most bear a ring on the stem, and many carry veil patches on the cap; they also grow from soil in the root zone of trees rather than on compost and stubble. Compare mature gill colour, print colour and the presence of a ring together, and note the habitat.
• Agaricus species have a ring and no volva, and their gills pass through pink to chocolate brown with a dark brown print.
• Leucoagaricus leucothites is white with a ring and no volva, its gills stay whitish or faintly pinkish, and its print is white to very pale pink.

A Working Sequence

Dig the base and confirm a loose white sac; check the stem for the complete absence of a ring; confirm free gills that ripen through salmon pink; test the cap for viscidity when moist; take a print and expect pinkish brown; and record the substrate as disturbed, nutrient rich open ground rather than woodland litter. If the cap is dry and streaked and the volva dark brown, you are looking at a different species.