Brown Puffball
Bovista nigrescens
Also called black bovist, blackening puffball, dark bovist
A round grassland puffball whose white outer skin peels away to reveal a shining purple-black inner ball. Larger than the Grey Puffball and equally prone to breaking loose and rolling.
Overview
The Brown Puffball is the largest of the common temperate Bovista species, forming smooth white balls 3-6 cm across in open grassland. Its identity becomes obvious with age: the white outer skin cracks and peels away in papery flakes to expose an inner ball of shining, dark purplish-black to blackish-brown, which then tears open irregularly at the top.
Like its relatives it has essentially no sterile base and no stalk, so nearly the entire fruiting body becomes spore powder. The attachment to the soil is slight, and mature specimens are frequently found detached, rolling among the grass tussocks or lodged in hedge bottoms.
It is a characteristic fungus of unimproved upland pasture and hill grassland in northern Europe, often fruiting alongside waxcaps and other grassland species that indicate long-established, lightly managed turf.
How to identify it
Fruiting body
Globose to slightly flattened or broadly egg-shaped, 3-6 cm across and occasionally larger. Young specimens are pure white and smooth, sometimes with a faint felty bloom.
Skin layers
The thin white outer layer weathers, cracks and sloughs off in papery flakes, revealing a tough, shining inner skin that is deep purple-black, blackish-brown or bronzed black. This dark, polished inner ball is the diagnostic feature.
Attachment and stipe
No stalk and no appreciable sterile base. The ball is joined to the turf by a small basal point with a few mycelial strands, which break to release the mature fruiting body.
Flesh and spore mass
White and firm within when young, becoming olive-yellow and finally a dense purple-brown powder occupying nearly the whole interior. Maturity brings an irregular, ragged opening at the apex through which spores escape. Spores in mass are purple-brown; like other Bovista species they bear a long pedicel visible under the microscope.
Where and when it grows
Grows on soil in grassland: hill and upland pasture, downland, unimproved meadows, machair, dunes, heaths and grassy woodland rides. It tends to prefer somewhat cooler, damper and less intensively managed grassland than the Grey Puffball, and is often abundant in northern and montane districts.
Distributed across Europe and much of temperate Asia and North America. Fruiting runs from summer through late autumn, and the durable black shells commonly overwinter and can be found the following spring.
Ecological role
This is a saprotrophic fungus of the turf layer, its mycelium decomposing grass roots, dead stem bases and soil organic matter. It is frequently part of the fungal community of ancient, low-input grassland where the sward has not been ploughed or heavily fertilised.
Spore dispersal is by tumbling. Once the anchoring threads part, the shell is rolled by wind and grazing animals, and each impact expels spores through the apical tear. The rigid, weather-resistant inner skin lets a single fruiting body keep dispersing spores across a whole winter.
Similar species
Bovista plumbea is smaller, usually 2-3 cm, and its exposed inner skin is lead-grey to bluish-grey rather than shining purple-black. Bovista pila of North America is bronze to purplish-bronze inside and hangs from a single conspicuous basal cord.
Lycoperdon pratense (also placed as Vascellum pratense) occurs in the same grassland but is top-shaped with a distinct spongy sterile base separated from the spore mass by a membrane, and it opens by a wide circular mouth rather than a ragged tear. Scleroderma earthballs are firm and heavy with a thick warty rind and a marbled dark interior from an early stage, never showing the white-flaking-to-black layered skin of Bovista.