Lion Shield Identification Guide

The Situation You Find It In

The scene is damp deciduous woodland in summer or early autumn, or increasingly a park bed mulched with ageing hardwood chips. Something small and startlingly yellow is standing up out of the debris on a thin pale stem. Cap perhaps 4 to 6 cm, chrome to golden yellow, slightly browner in the middle; stem white and slim; no ring, no sac at the base, no cobweb.

Before anything else, establish what it is growing out of. Pluteus species are wood-rotters, and Lion Shield is no exception, but the wood is often invisible: a branch buried under leaf litter, a rotted root, a stump ground down to soil level, a chip mulch that has weathered to a brown crumb. Clear the litter away with your fingers and follow the stem base down. If it terminates in wood or wood fragments, you are in the right genus group. If it genuinely rises from mineral soil among grass, think again.

Working Through the Cap

The cap starts conical to bell-shaped and opens to convex and then almost flat, usually keeping a low broad umbo at the centre. Diameter is typically 3 to 7 cm, occasionally a little more.

Colour is the obvious feature and also the trap: bright chrome-yellow to golden or olive-yellow overall, generally with a duller ochre or olive-brown disc, and the whole thing fades markedly in dry weather and with age, so a sun-bleached one can look almost tan. The surface is dry and matt, never sticky, and under a hand lens it is finely velvety. At the centre it is often minutely wrinkled or veined in a radial pattern, which is a genuinely useful character once you learn to see it. When the cap is wet, the outer part becomes slightly translucent so that the gills show through as fine lines running in from the margin. The margin itself is thin, often faintly grooved, and paler than the disc.

The Gills: Free Is the Word That Matters

Turn the cap over. In Pluteus the gills are free, meaning they stop short of the stem and leave a narrow circular gutter around its apex. Cut a fruit body in half lengthways to confirm this rather than judging it from underneath, because crowded gills can appear to touch the stem when they do not.

They are crowded, fairly broad, swollen in the middle, and their colour changes as the spores mature: white to cream in young caps, then flesh-pink, then a dull pinkish-brown in fully mature material. The gill edge is finely fringed under a lens and is often paler, sometimes with a yellow tinge. There is no partial veil, so young gills are exposed from an early stage and never covered by a membrane.

Stem and Base

The stem is 4 to 8 cm long and only 3 to 8 mm thick, more or less cylindrical, sometimes slightly thickened downward but never bulbous. It is white to cream, occasionally with a faint yellow wash at the extreme base, and is covered in fine longitudinal fibrils; some collections show darker brownish fibrils, particularly on the lower half.

Run through the negatives deliberately, because they are diagnostic: no ring, no ring zone, no cobwebby cortina, no volva or sac, no marginate bulb. The base sits directly on or in the wood, sometimes with a little white mycelial felt binding wood fibres. The stem is fibrous and snaps with a clean fibrous break.

Flesh and Colour Change

Slice the fruit body from cap to base. The flesh is thin, white to very pale yellow directly under the cap cuticle, and it does not change colour on exposure; at most the stem base shows a slightly deeper yellow tone. There is no milk, no bluing, no reddening. The smell is faint and hard to pin down, at most slightly earthy or faintly radish-like. Old caps become watery and collapse quickly, so work with fresh material.

Taking and Reading the Spore Print

The spore print is not optional here; it is what turns a yellow mushroom on wood into a Pluteus. Choose a cap that has flattened out, cut the stem off flush with the gills, and lay the cap gills-down on a sheet of paper that is half white and half dark, or on a glass slide. Cover it with a cup or bowl so the cap does not dry, and leave it two to six hours. Overnight is fine but the cap may deliquesce into a mush.

The print is pink: salmon, flesh-pink, sometimes drifting to pinkish-brown as it dries. Do not attempt to judge this from the gills of a young cap, because those are white and will send you to entirely the wrong family. Under the microscope the spores are broadly ellipsoid to nearly round, smooth, and not amyloid.

The three-part combination of free gills, a pink print and a wood substrate places you in Pluteus with near certainty. Within Pluteus, the bright yellow cap with a white stem then does most of the remaining work.

Substrate and Season

Lion Shield is a saprotroph of well-rotted deciduous wood. Beech, birch, alder, willow and poplar are all recorded, and it takes readily to hardwood chip mulch and sawdust heaps, which is why urban records have increased. It fruits from late spring through to autumn, with a summer peak in warm regions, and appears singly or in small scattered groups rather than in dense tufts. It is never associated with living tree roots as a partner, so a specimen genuinely growing in turf away from wood should push you elsewhere.

Separating the Close Look-Alikes

Pluteus romellii is the main confusion. It is generally smaller, with a browner or olive-brown cap that carries only a yellow undertone, and, decisively, a bright chrome-yellow stem. Stem colour splits the two: leoninus keeps a white to cream stem.

Pluteus chrysophaeus and its allies in the yellow-brown group have duller, browner caps with a wrinkled centre and a whitish stem. They overlap awkwardly and this pair is where a microscope earns its keep, since the cap skin of leoninus is built of long upright hair-like cells while chrysophaeus has a surface of rounded cells. Macroscopically, leoninus is brighter and more evenly yellow.

Pluteus cervinus, the common Deer Shield, is much larger and stouter, with a fibrillose brown cap and no yellow at all, and its gill edge is dark brown under a lens.

Bolbitius titubans, the Yellow Fieldcap, looks superficially similar in colour but has a slimy, sticky, extremely thin cap that collapses within hours, gills that are narrowly attached to the stem rather than free, and a rusty cinnamon spore print. It grows in grass, on dung or on straw, not on rotten logs.

Gymnopilus species can be yellow-orange on wood, but the gills are attached, the spore print is rusty orange-brown, and they usually grow in dense clusters with a ring zone.

Hypholoma fasciculare is also on wood, but in tight tufts, with attached greenish-sulphur gills and a purple-brown print.

A small yellow Amanita would have white spores, a ring and a bulbous base with volval tissue, all of which the base test finds immediately.

What to Record

Photograph the cap surface close enough to show the wrinkling, the underside showing free gills, the whole stem including its base and substrate, and the finished spore print. Note whether the stem carries any yellow, because that one detail resolves most of the genus.