Candlesnuff Fungus Identification Guide

The Setting and the First Impression

You find this on dead wood, and specifically on the well-rotted stumps, fallen branches and buried timber of broadleaf trees. Cut stumps in managed woodland are the classic site, along with log piles, fallen limbs in leaf litter, old fence posts in damp shade, and the sawn ends of felled trunks. It is a fungus of shade and moisture, and it persists through the winter when almost everything else has gone, which is why it is so often the only conspicuous fungus on a January woodland walk.

The first impression is of a small black-and-white forest sprouting from wood: dozens of stiff, upright, flattened prongs 2 to 8 cm tall, black at the bottom and frosted white at the top, crowded together on a stump face or scattered in lines along a rotting branch. The silhouette is antler-like, and the black-to-white gradient is visible from several metres. Nothing about it is fleshy — from the first glance it reads as something dry, hard and structural rather than as a soft mushroom.

Understanding What You Are Looking At

This is not a gilled mushroom or a bolete. Xylaria hypoxylon is an ascomycete, and what you are holding is a stroma: a tough, compound structure of fungal tissue in which the spore-producing bodies are embedded. That single fact restructures the whole identification, because the questions you ask of an agaric — cap, gills, ring, volva — simply do not apply. Instead you read the outline, the surface texture, the colour zoning, the internal structure in section, and the way the surface changes as it matures.

The Shape and Branching

Measure the height: usually 2 to 8 cm, occasionally taller in sheltered spots. The individual stroma is flattened and strap-like rather than round in cross-section, and the tip is where the variation lies. Some are simple, unbranched spikes with a pointed or slightly flattened apex. Many fork once or twice into a two- or three-pronged fork. Others develop into a genuine flattened antler with several irregular fingers, or into a broad spatula shape with a crimped upper edge. All of these can occur on the same piece of wood, so do not treat any one outline as diagnostic; the tendency to be flattened and irregularly forked, rather than cylindrical and regularly branched, is the character to record.

The Two-Tone Surface and How It Changes

Read the fruitbody from base to tip. The lower portion, roughly the bottom third to half, is black or very dark brown and finely felted or velvety, with a matt, sooty look and a slightly hairy feel under a lens. Above that, the young stroma is coated in a whitish to pale grey powder, dense at the tips and thinning downward — this is a mass of asexual spores produced on the surface, and it is what gives the fungus its snuffed-candle-wick appearance. Wipe a tip with a fingertip and the white comes away, leaving a darker surface beneath.

As the season advances the white coating is lost and the whole structure blackens. Mature stromata are uniformly black, slightly swollen in the upper part, and their surface becomes minutely pimpled or roughened, like coarse sandpaper or the skin of a small blackberry. Each of those pimples is the raised mouth of an embedded flask-shaped chamber where the sexual spores are produced. Rolling a mature stroma between finger and thumb, you can feel the granular texture clearly. Finding both the white-tipped young state and the black pimpled mature state on the same substrate is the ideal confirmation.

Texture and Section

Pick one and bend it. The stroma is tough, leathery and pliant — it flexes and springs back, and it resists tearing, quite unlike the brittle snap of a coral fungus or the soft collapse of an agaric. Old stromata dry hard and stay standing on the wood for months.

Now cut one lengthwise with a sharp blade. In section you should see a thin black outer rind enclosing a firm white to off-white interior, giving a stark black-and-white contrast. In mature material, look along the outer rind with a lens for a row of small rounded cavities just beneath the surface — the flask-shaped perithecia, each opening by a tiny pore at one of the surface pimples. That sectional view is the most decisive single observation available in the field.

Taking and Reading a Spore Deposit

A conventional spore print is impossible because there is no cap to lay down, but a deposit can still be obtained. Choose a fully mature, entirely black, pimpled stroma. Lay it on white paper, or stand it upright against a white card, and cover the whole thing with a glass or a plastic box to keep the air humid and still. Leave it overnight.

The result is a sooty grey to black deposit, usually as fine smudges or short streaks alongside the stroma rather than as a clean silhouette, since the spores are shot sideways from the perithecial pores rather than dropped vertically. Under a microscope the spores are dark brown to black, smooth, and distinctly bean- or spindle-shaped with one flattened side. A white powdery deposit from a young white-tipped stroma is a different thing altogether: those are asexual conidia, not the sexual spores, and they are worth noting separately.

Substrate, Season and Ecology

Xylaria hypoxylon is a saprotroph and a white-rot decomposer, breaking down lignin and cellulose in dead broadleaf wood and leaving the residue pale, soft and fibrous. Beech, birch, oak, ash, hazel and willow are all frequent hosts, and buried wood counts, so a group apparently arising from soil usually proves to be attached to a root or a fragment of branch just below the surface. Probe with a finger before recording it as terrestrial.

Stromata can be found in every month, but young white-tipped material is most frequent in late summer and autumn, and blackened mature material dominates through winter and into spring. Colonies are long-lived and a single stump can carry the fungus for several seasons in a row. Look also for the black zone lines it draws inside the decaying wood: split a colonised log and you may see thin dark boundaries marking territory between neighbouring mycelia.

Separating It From Look-alikes

Xylaria polymorpha shares the black rind and white interior but is entirely different in outline: thick, blunt, club- or finger-shaped, several centimetres wide, arising in tight groups from stumps, and never producing the flattened white-frosted antlers.

Xylaria longipes is slimmer than polymorpha, with a distinctly narrowed stalk-like base and a smooth club head, most often on fallen sycamore and maple branches; it is cylindrical rather than flattened and never white-tipped.

Xylaria carpophila is the closest in form but far more slender, a thread-like black stalk with a small pale tip, and it grows specifically from the rotting cupules of beech mast in the litter — check the substrate and the diameter and the two separate easily.

Coral and club fungi such as Clavaria, Clavulina and Ramaria can look superficially antler-like, but they are soft, brittle, fleshy and pale throughout, snapping cleanly with no black rind and no white core contrast, and they grow from soil or moss rather than from wood.

Calocera species also branch and grow on wood but are yellow to orange, gelatinous and rubbery when moist, and horny when dry.

Anything with a black surface but a rounded, cushion-like or crust-like form spread flat on the bark belongs to related genera such as Hypoxylon or Annulohypoxylon rather than to Xylaria.

Quick Field Checklist

Erect, flattened, antler-like or simple spike-shaped stromata 2 to 8 cm tall on dead broadleaf wood; black felted lower portion; white powdery upper portion in youth, becoming entirely black and minutely pimpled at maturity; tough leathery texture; black rind over a white interior in section; sooty black spore deposit; present all year, most conspicuous in autumn and winter.