Yellow Stagshorn Identification Guide

The first impression

Autumn, a dark conifer plantation, and a splash of egg-yolk yellow on a mossy stump stops you mid-stride. Calocera viscosa is one of the easiest woodland fungi to spot and one of the easiest to misfile, because at twenty paces it reads as a small coral fungus. Get down to it and the impression changes: it is glossy, slightly slimy in wet weather, and when you press a branch between finger and thumb it gives like rubber and springs back rather than crumbling. That single tactile fact, gelatinous-tough rather than brittle or fleshy, moves it out of the true club and coral fungi and into the jelly fungi.

The setting that supports the identification

The substrate is close to diagnostic. Calocera viscosa is a wood-rotting fungus of conifers, and you will find it on rotting spruce, pine, larch and fir stumps, on fallen conifer trunks, and very often apparently growing straight out of the soil, moss or needle litter. In that last case it is not on soil at all: it is attached to a buried root or a fragment of decaying conifer wood beneath the surface. It is common in plantations and native pinewoods, frequent from late summer through autumn and lingering into early winter, and it often fruits in scattered troops of dozens across a single decaying stump.

Working through the fruit body

Overall form. Erect and antler-like, three to eight or occasionally ten centimetres tall, arising singly or in small tufts. The base is a simple stalk that divides once and then divides again, usually two or three times in all, into slender, tapering, upright branches. The tips are pointed and frequently forked into two fine prongs, giving the stag-antler silhouette that names the species.

Colour. A saturated egg-yellow to golden or orange-yellow when fresh and moist. Colour deepens toward orange in exposed positions and in cold weather. On drying the whole fruit body shrinks, hardens and darkens to a deep orange or almost brick tone, becoming horny and surprisingly tough; it will revive and swell again after rain, which is characteristic of the jelly fungi as a group.

Surface. Smooth, greasy to distinctly viscid when wet, shining when dry. There are no pits, wrinkles, veins, teeth or gills anywhere; the entire outer surface of the upper branches is fertile.

Texture. Gelatinous and elastic. A branch bends double without snapping and returns to shape. Tear it and it parts with a slightly rubbery resistance rather than a clean brittle break.

The base. This is the test worth learning. Grip the fruit body at the bottom and pull steadily. Calocera viscosa has a whitish, tapering, root-like base that extends downward into the wood, and it draws out of the substrate like a small tap root. That white rooting base, contrasting with the yellow above, is the single most useful field character and is absent in almost all of the things it is confused with.

Flesh. Concolorous or slightly paler inside, translucent, with no colour change on cutting, no milk and no latex.

Spores and microscopy

A spore deposit is possible if you stand a fresh fruit body upright over dark card in a humid box overnight; the deposit is pale yellowish, and against white card it may be almost invisible. Under the microscope the identification is unambiguous. The basidia are tuning-fork shaped, deeply forked into two long prongs, which is the defining feature of the Dacrymycetes and separates the group from every gilled and coral fungus, whose basidia bear four short sterigmata. The spores are cylindrical to slightly curved, sausage-shaped, roughly 8 to 12 by 3 to 5 micrometres, and become one-septate at maturity, so mature spores show a single cross wall dividing them into two cells. Hyphae have clamp connections.

Ecology

The fungus is a saprotroph and a wood decayer, colonising conifer heartwood and roots and contributing to brown rot as the wood breaks down into cubical fragments. It is a late-stage coloniser, appearing on stumps that have already been softened by other fungi, and a single stump can support fruiting for several consecutive autumns. Its restriction to conifer wood is strong enough that a yellow antler fungus on oak or beech should be identified as something else until proved otherwise.

Separating the look-alikes on morphology alone

• Calocera cornea is the small relative: unbranched or barely forked yellow spikes only a few millimetres to a centimetre tall, growing in dense rows along the cut faces and cracks of broadleaved wood, especially beech and birch. Size, lack of branching and the hardwood substrate settle it.
• Calocera pallidospathulata forms pale ochre to buff spatula-shaped or flattened blades rather than tapering antlers, and it is duller and less saturated in colour.
• Clavulinopsis species such as C. fusiformis and C. helvola grow on soil in grassland, are fleshy and brittle rather than rubbery, and snap cleanly when bent. C. fusiformis makes tight bundles of unbranched spindles.
• Ramaria species, including the yellow ones, are much larger, distinctly fleshy, crumbly rather than elastic, and grow from soil in a broad cauliflower-like mass with many more branch orders.
• Tremella mesenterica shares the jelly texture and yellow colour but forms brain-like folded lobes or seaweed-shaped masses rather than erect antlers, has no rooting base, and grows on hardwood attached to the bark surface.
• Dacrymyces species are cushion-shaped or blob-like rather than branched.

A quick decision path

Ask four questions in order. Is it on conifer wood, including buried wood? Does it bend like rubber instead of snapping? Does it branch repeatedly into pointed, often forked tips? Does a white root-like base pull out of the substrate? Four yes answers give Calocera viscosa with no microscopy required. If the texture is brittle or fleshy, move to Clavulinopsis or Ramaria; if the substrate is hardwood, look at Calocera cornea and Tremella instead.