Mosaic Puffball

Mosaic Puffball (Calvatia utriformis, also known as Handkea utriformis and Lycoperdon utriforme) is a broad, squat, sack-shaped puffball of open ground. Its epithet utriformis refers to a wineskin or leather bottle, describing the wide, slightly flattened head on a short thick base.

The field character that names it in English is the surface: an initially white, felted skin that breaks up as the fruit body expands into a network of flat-topped polygonal scales and warts, like coarse crazy paving or a tiled mosaic. Between the scales the paler underlying wall shows through.

Mature fruit bodies lose the upper part of the wall entirely, and the thick sterile base persists in the turf for months as a shallow grey-brown bowl.

Fruiting body

Broad and squat, 5–12 cm across and 5–10 cm tall, the head wider than tall and slightly flattened above, abruptly narrowing into a short, thick, furrowed sterile base.

Surface

White to cream and finely felted or granular when young, soon breaking into a mosaic of polygonal scales and low pyramidal warts. With age it dulls to greyish, tan and finally olive-brown, and the scaly pattern becomes more pronounced.

Interior and spore mass

White and firm when young, then yellowish, olive and finally powdery olive-brown to greyish brown. The sterile base is spongy, chambered and separated from the spore mass, remaining as a firm mass after dispersal.

Opening and remains

The upper wall breaks down and blows away in fragments, leaving a broad, thick-walled, cup- or bowl-shaped base that survives in the sward long after the season.

Spore print

Not applicable in the usual sense; the mature spore mass is olive-brown.

The Mosaic Puffball is a fungus of open, well-drained grassland: upland pasture, heathland, coastal dunes, links, commons, short grazed turf and sandy grassland. It avoids woodland and rank vegetation, and often fruits in scattered groups or loose arcs.

Fruiting occurs from summer into autumn, and the empty bowl-shaped bases can be found in the same turf right through winter and into the next spring. It is widespread across Europe, North America and temperate Asia.

This species is a grassland saprophyte, decomposing dead roots, thatch and humus in the upper soil of pastures, heaths and dunes. Its long-lived mycelium tends to reappear in the same patches for many years, so a known site is often productive season after season.

Spore dispersal is passive and wind-driven. Once the mosaic-scaled upper wall disintegrates, the exposed spore mass is stripped away by wind and rain over a period of weeks, leaving the durable basal bowl behind.

Vascellum pratense is much smaller, has a smoother granular surface, and shows a distinct membranous diaphragm inside separating spore mass from base. Calvatia cyathiformis is similar in stature but ripens to a purple-brown spore mass and has a deeper vase-shaped persistent base. Calvatia excipuliformis is taller with a long pestle-like stalk rather than a short thick base. Bovista species are smaller, more or less spherical, lack a well-developed sterile base and expose a papery grey inner wall.

The coarse polygonal mosaic scaling on a squat grassland puffball with olive-brown spore powder is the deciding combination.