Grey Puffball Identification Guide

The Setting and the First Look

Grey Puffball is a grassland fungus, and the habitat does a lot of the identification for you. Think closely grazed pasture, a coastal dune slack, a mown lawn, a chalk down cropped by rabbits or a sandy playing field. From a distance the young fruit bodies look like small white marbles or golf balls resting on the turf, and the older ones look like little grey paper lanterns lying loose among the grass stems, sometimes drifted into hollows because the wind rolls them.

Crouch down and check the attachment before you pick anything. A Grey Puffball sits almost on top of the ground, held only by a single slender cord of mycelium at one point on the underside. There is no stalk, no swollen base and no tapering pillar of tissue pushed into the soil. Old specimens have already snapped free and are entirely detached.

Reading the Outside

Size is modest: 1.5 to 3.5 cm across, occasionally 4 cm. The shape is close to a perfect sphere, sometimes slightly flattened on top or a little wider than tall. There are no spines, no pyramidal warts, and no ornamental scales.

The wall is built in two layers, and watching them behave is the core of the identification. In young material the outer layer, the exoperidium, is white to cream, smooth or very finely mealy, and slightly floury to the touch. As the fruit body matures, that outer layer cracks into small irregular patches and flakes off, sometimes in a day or two, leaving pale remnants clinging in a mosaic. Underneath is the inner layer, the endoperidium: thin, papery, tough, faintly shiny, and a clean lead grey, pewter or bluish grey. That colour gives the species its name and, in grassland, immediately narrows the options.

At maturity the fruit body opens by a single aperture at or near the apex. It forms by irregular tearing and expands into a ragged mouth; it is not a neat, pre-formed circular pore with a tidy raised rim. Squeeze a mature ball gently and a smoky brown cloud puffs out.

Sectioning: the Decisive Step

Carry a knife and cut a young fruit body vertically from top to bottom. This one action separates Grey Puffball from most of its confusables.

What you should see is a solid, uniform, pure white interior with the texture of firm cheese or marshmallow, filling the entire ball right down to the point of attachment. There is no sterile base, no columella, and no membrane dividing the ball into an upper spore chamber and a lower cushion of tissue. There is also no outline of a folded cap, gills or stipe, which is what an unexpanded agaric egg would show in section.

Watch the maturation sequence across a colony: white becomes yellowish, then olive, then finally a dark umber to purplish brown powder mixed with springy threads of capillitium. Fruit bodies at the yellowing stage feel spongy and slightly damp; fully mature ones are dry and rattle-light.

Reading the Spores

Puffballs do not drop a spore print in the conventional way. Instead, tap a ripe fruit body over a sheet of white paper and you get a fine brown dust, or simply mount a scrap of the mature gleba in water on a slide.

Two microscopic characters confirm Bovista. First, the spores are globose to broadly ellipsoid, minutely warted, and most of them carry a long, tapering, colourless pedicel, a tail of up to 10 to 12 micrometres left over from the sterigma. That pedicel is the giveaway for the genus. Second, the capillitium is of Bovista type: discrete, free-floating branched units with a thick main trunk that divides repeatedly into finer, tapering, sharply pointed tips, rather than a continuous tangled network attached to the wall as in Lycoperdon.

Substrate and Season

This is a saprotroph of short, well-grazed or mown grassland with low nutrient input. Chalk and limestone downland, fixed dunes and dune grassland, machair, coastal cliff-top turf, old lawns, churchyards and long-established verges are the productive places. It avoids rank, tussocky grass and does not grow on wood, dung or deep woodland litter.

Fruiting runs from early summer through to late autumn, which is earlier and longer than many grassland fungi, and the tough grey shells persist for months afterwards. In winter you will often find last season's empty grey husks caught in tufts of grass, which is a useful sign that the site is worth revisiting in season.

Separating the Look-Alikes on Morphology

Bovista nigrescens. The closest relative and the main confusion. It is larger, typically 3 to 6 cm, its outer white layer peels away in bigger sheets, and its inner wall matures to a dark purplish-black or bronzed brown rather than lead grey. If your ball is big and nearly black, it is nigrescens.

Vascellum pratense. Shares grassland habitat but is pear-shaped to top-shaped with a distinct sterile base, and in vertical section a clear membrane, the diaphragm, separates the spore mass from the spongy basal tissue. That membrane is unmistakable once you have seen it.

Lycoperdon species. Pear-shaped or pestle-shaped with a stalk-like sterile base, a surface bearing spines, granules or warts, an interior showing a chambered sterile base beneath the spore mass, and a neat pre-formed apical pore. They also stay firmly rooted rather than breaking free.

Calvatia and Handkea species. Much larger, with a substantial stalked or lobed base, and they open by irregular collapse or cracking of the whole upper wall rather than through a small apical mouth.

Scleroderma species. Superficially spherical but with a thick, hard, warty, ochre to yellow-brown rind, an interior that turns firm and purple-black very early with a marbled pattern, and a habitat of woodland edges, heath and sandy banks rather than short turf.

Unexpanded agaric eggs. Any small white ball found in grass should be cut in half. An immature agaric shows a compressed cap, gill tissue and a stipe in outline; Grey Puffball is uniformly white and structureless throughout.

Pisolithus and Bovistella types. Pisolithus is larger with a stalk and an interior of distinct pea-like peridioles in a black matrix, quite unlike the homogeneous gleba here.

Field Checklist

Short turf, summer to autumn. Ball 1.5 to 3.5 cm, stalkless, attached by a single cord that soon snaps. White mealy outer skin flaking away to expose a papery lead-grey inner wall. Irregular torn apical mouth. Section uniformly white with no sterile base and no diaphragm. Mature gleba dark brown and powdery. Spores warted with a long pedicel; capillitium of free branched units.