Pear-shaped Puffball Identification Guide

The Setting and the First Impression

Substrate alone gets you most of the way with this species. You are in woodland, on a wooded bank or in a park, standing over a decaying stump, a fallen trunk that has gone soft, a heap of old logs or a patch of ground where buried timber lies just beneath the surface. Across the wood is a crowd of small, pale, top-shaped bodies, often dozens together and sometimes hundreds, packed so closely that they press each other out of shape. The overall impression is of a colony rather than a scatter, and that packed, communal growth directly on wood is the first and best clue, because almost every other common puffball comes up singly or in loose groups from soil.

Reading the Outer Surface

Pick out an average individual. It is small, two to four and a half centimetres across and perhaps as tall, and shaped like a pear or a spinning top: a rounded head narrowing rather abruptly into a short, pinched, stalk-like base. Young fruitbodies are white to cream, becoming ochre, dull tan, buff or finally olive-brown as they age.

Run a fingertip over a young one. The surface is not smooth but covered in a fine granular or minutely warty coating, made of tiny mealy grains and very short blunt spines, all more or less the same size and never long, coarse or pyramidal. That coating rubs off easily and weathers away, so mature fruitbodies become nearly smooth, dull brown and slightly leathery or papery, sometimes with a faint net-like patterning where the granules used to sit. Do not expect the neatly ornamented, scar-patterned surface that other puffballs develop when their spines drop; here the surface just becomes plain.

At maturity a single small opening, the ostiole, forms at the very top. It begins as a soft darkened spot, then tears into a round or slightly ragged pore through which a puff of dust escapes when the wall is tapped by a raindrop or a fingertip.

The Base and the Cords

Now do the thing that settles the identification. Ease a fruitbody away from the wood, taking the base with it, and look underneath. In this species the pinched base runs into stout white mycelial cords, sometimes described as roots or rhizomorphs, which spread across the wood surface and knit neighbouring fruitbodies together. They are conspicuous, cottony to string-like, brilliant white when fresh, and often several centimetres long. Lifting a clump usually brings up a whole mat of them. No other common small puffball shows anything comparable.

Reading the Interior

Cut a fruitbody in half from top to bottom with a sharp knife, and do this on both a young and an older specimen if you can. In a young fruitbody the interior is firm, uniformly white and cheese-like, with no internal structure at all: no chambers, no outlines, no dark core. As it matures, the upper part yellows, then turns olive-green and finally olive-brown, and its texture goes from firm to cottony to a dry powder of spores mixed with fine threads. The lower, stalk-like part remains as a small sterile base, which in this species is compact and only slightly spongy, occupying much less of the fruitbody than in some relatives, and it is separated from the spore mass by a thin floor. Checking that the young interior is pure white and structureless is important, because it eliminates several unrelated things.

The Spore Mass Rather Than a Spore Print

Puffballs do not shed spores from an exposed surface, so a conventional spore print is not possible. The equivalent step is to sample the spore dust. Hold a mature fruitbody over a sheet of white paper and tap it so a cloud escapes through the pore, or slit the wall and shake the powder out. The dust is olive-brown, fine and slightly greasy to the touch, and it drifts a long way. Under a microscope the spores are globose, smooth or nearly so, and pale olive, mixed with abundant thread-like elements that make up the internal cotton.

Substrate and Season

This is a wood-rotting saprotroph. It fruits on rotting stumps, fallen logs, buried roots, sawn timber left in contact with the ground and old woody debris of both broadleaved and coniferous trees, occasionally appearing to grow from soil where it is actually working on wood underground. If you think you have this species on open turf, dig: you will usually find timber. The fruiting season runs from midsummer to late autumn, and because the outer wall becomes tough and papery, weathered brown husks persist on their stumps right through winter and can still be identified months after they matured.

Separating the Look-alikes on Morphology

The common ground-dwelling puffball with the same general pear shape is the main confusion. It grows on soil and litter, not on wood, lacks the white cords, and is covered in prominent conical spines of two clearly different sizes, which fall away and leave a distinctive net of pale scars over the surface. Its sterile base is also more developed and coarsely chambered.

Other small ground puffballs, including the darker-spined species of heaths and acid woodland, likewise grow from soil, have coarser or darker ornamentation and lack basal cords. The long-stalked puffballs are much larger, with a distinct elongated pseudostalk, and rupture by the whole top breaking away rather than through a neat pore.

Earthballs are a firmer separation. Their wall is thick, tough, rind-like and usually coarsely scaly or cracked, they have no defined pore and simply split irregularly, and, most decisively, cutting one open reveals a hard interior that turns purplish black or nearly black very early, often while the outside still looks young. Any dark, marbled or firm interior in a small young specimen rules this species out.

Finally, always halve anything round and white found near soil. A young Amanita egg cut vertically shows the complete outline of a developing mushroom inside, with a miniature cap, gills and stalk drawn in cross section, and a distinct outer skin. A young puffball of this species shows nothing but uniform white tissue.

A Field Sequence

A dense troop directly on rotting wood; small pear or top-shaped fruitbodies with a pinched base; a fine granular to minutely spiny surface that weathers smooth; conspicuous white cords binding the bases together; a single apical pore at maturity; a uniformly white, structureless young interior turning olive-brown and powdery; a small compact sterile base; olive-brown spore dust.