Silky Rosegill Identification Guide

The first impression

Silky Rosegill announces itself by size and setting. You usually meet it on made ground rather than in old woodland: a compost heap, a manured field margin, a garden bed, a fresh wood-chip mulch, a roadside verge that has been scraped and reseeded, or the edge of a straw stack. From a distance a mature specimen looks like a big pale mushroom with an oddly greasy shine, ten to fifteen centimetres across, standing tall on a slim white stalk. Often several appear in a loose troop across disturbed soil. The character that stops you is the underside: gills that are free of the stipe and, once mature, a strong salmon-pink that reads as almost rose-brown against the white stalk. The mushroom is soft and rather fragile for its size, and the cap surface, if you touch it when damp, is slick enough to make your fingertips shine.

Reading the cap

Start with shape. Young caps are egg-shaped or bluntly conical, becoming broadly convex, then flat with a low central hump and finally slightly upturned at the rim in old age. Diameter is commonly five to fifteen centimetres and can exceed twenty in rich ground. The colour is variable and this trips people up: pure white in shaded, sheltered specimens, but more often pale mouse-grey, silvery greyish-brown, or a warm greyish-buff, always darkest at the centre and fading outwards. The surface is smooth, hairless, and coated with a thin gluten that makes it viscid to positively slimy in wet weather; when it dries out it becomes shining and silky, which is where the common name comes from. Dried caps often show fine innate radial fibrils. There are no scales and no veil scraps left on the rim, and the margin is even, not striate, occasionally splitting radially in old, wind-dried specimens.

The gills

Turn it over and check attachment first. The gills are free, ending in a clean gap around the top of the stipe so that a narrow moat separates them from it. They are crowded, quite broad and swollen in the middle, with finely fringed or flocculose edges visible under a lens. Colour follows a strict sequence: white in unopened buttons, then cream, then a pink flush, then a deep, saturated salmon or rose-brown at maturity. There is no cobwebby veil covering them in the button, only the outer wrapper described below.

Stipe, base and the volva

The stipe is the decisive part of the mushroom, and it must be dug rather than picked. It is five to twenty centimetres tall, one to two centimetres thick, white, smooth to finely silky-fibrillose, tapering upwards from a swollen base, and solid rather than hollow. There is no ring anywhere on it, and no zone of fibrils where a ring once was. Trowel the soil away from the bottom and you should expose a loose, membranous, sac-like bag from which the stipe emerges. This volva is white to dirty greyish-brown, thin, lobed at the mouth, and often stained with soil or compost. It is the remains of a universal veil that enclosed the whole young mushroom, and it is free from the stipe, more like a bag the stalk was slipped into than a collar attached to it. If you snap the mushroom off at ground level you lose the single most diagnostic feature, so always lever it out whole.

Flesh, section and smell

Cut a mature specimen from cap edge to stipe base. The flesh is white and soft, thick over the disc and thinning to the margin, and it does not change colour on exposure: no reddening, no blueing, no browning beyond a slow dulling. The stipe flesh is white and fibrous. The odour is faint and slightly earthy or radish-like, not distinctive enough to identify on, but the absence of any strong farinaceous or chemical smell is itself a data point.

Spore print technique

Because the genus hinges on spore colour, take a print from a cap that has flattened but is not yet collapsing. Remove the stipe, lay the cap gills-down on white paper, cover it, and leave it a few hours. The deposit is a rich pink, deeper and browner than the salmon of the gills themselves, often described as dull rose-brown. Two practical points: a slimy cap can stick to the paper, so lay it on a matchstick tripod if you can, and always judge the colour once the print has dried, since wet deposits look darker.

Substrate and season

This is a saprotroph of rich, nitrogen-loaded, disturbed ground. It has no tree partner, so it turns up in gardens, allotments, compost, manured pasture, silage residue, wood chip, straw and freshly landscaped soil far from any wood. Fruiting is long, from late spring through to the first hard frosts, with a strong autumn peak, and populations can appear suddenly after mulch is spread. If a suspected Silky Rosegill is growing directly out of a log, branch or stump, the identification is wrong.

Separating it from look-alikes on morphology alone

The combination to hold in mind is: free gills, pink print, volva present, ring absent, growing on soil. Change any one of those and you are somewhere else.

Amanita species also have a volva, but their gills stay white or cream to the end, they drop a white print, most have a ring on the stipe, many carry warty patches of veil on the cap, and they are mycorrhizal partners of trees rather than residents of compost. Cut through a young Amanita and the gills never flush salmon.

Pluteus species share the free gills and the pink print but have no volva at all, and they grow on wood, logs, sawdust and buried timber. The Deer Shield is the common one, with a dry, dark brown, fibrillose cap.

The small Volvariella species have the same architecture in miniature: Volvariella pusilla and its allies are only a couple of centimetres across with dry, silky-hairy white caps, while Volvariella surrecta grows on the rotting caps of other mushrooms. Silky Rosegill is much larger and its cap is viscid, not hairy.

Agaricus species have free gills too, but the gills pass through pink to chocolate-brown, the print is dark brown, there is a well-developed ring, and there is no volva. Leucoagaricus and Chlorophyllum have a ring, scaly caps and white or green prints. Stropharia rugosoannulata, another rich-soil mulch species, has attached gills, a thick radially split ring, and a purplish-black print.