AT A GLANCE
- Common Name: Black Bulgar
- Scientific Name: Bulgaria inquinans
- Category: Fungi
- Subcategory: Cup Fungi
- Range: Widespread across temperate and boreal forests of Europe, North America, and temperate Asia, following the distribution of mature oak and chestnut trees
- Habitat Type: Broadleaved deciduous forests, ancient woodlands, and timber yards, fruiting exclusively on the bark of recently felled or dead oak (Quercus) and chestnut trunks and large boughs
- IUCN Red List Status: Least Concern
- Lifespan: Fruiting bodies persist for 4 to 8 weeks; mycelium lives for years inside deadwood
- Diet: Saprobic (wood-decay ascomycete breaking down dead deciduous timber, especially oak bark and sapwood)
- Average Size/Weight: Apothecia (cups) diameter 1 to 4 cm; height 1 to 2 cm; often growing in dense crowded clusters
- Key Defining Feature: Distinctive, gelatinous, rubbery cup fungus resembling glossy black drops of tar or shiny licorice drops bursting out through cracked oak tree bark
Overview
Black Bulgar (Bulgaria inquinans), playfully known to mycologists as the ‘Rubber Buttons’ or ‘Black Jelly Drops,’ is a fascinating and unmistakable wood-decay ascomycete native to the temperate forests of the Northern Hemisphere. Typically bursting forth in crowded clusters from the furrowed bark of fallen oak logs, this curious fungus looks like shiny dollops of black tar, rubber buttons, or licorice candies. Unlike soft jelly fungi, it possesses a firm, tough, elastic texture and leaves a dense sooty black stain on hands when handled.
Biology and Physical Characteristics
Bulgaria inquinans produces fruiting bodies (apothecia) that begin as rounded, spherical, dull brown or rusty-scurfy buttons emerging through ruptures in tree bark. As they mature, the tops flatten out and expand into shallow cups or top-shaped discs measuring 1 to 4 cm in diameter. The upper spore-bearing surface (the hymenium) is pitch-black, extraordinarily smooth, and shiny when moist, contrasting with the dark brown, velvety or granular outer surface. The interior flesh is tough, gelatinous-elastic, and rubbery, retaining water during dry spells. Its specific name inquinans means ‘staining’ or ‘polluting,’ referring to the copious sooty-black ascospores that rub off like printer’s ink on fingers or clothing.
Behavior and Ecology
Black Bulgar is an obligate saprotroph that plays an essential primary role in decomposing the coarse woody debris of broadleaved trees, almost exclusively English oak (Quercus robur), sessile oak (Q. petraea), and sweet chestnut (Castanea sativa). It specializes in colonizing dead logs and fallen trunks that have been down for only one to three years, fruiting from late summer through winter after periods of persistent rain. The apothecia forcibly eject millions of microscopic ascospores into passing air currents when stimulated by drying winds or humidity changes, coating surrounding bark in a fine black dusting.
Conservation and Human Impact
Black Bulgar is evaluated as Least Concern on European and regional fungal red lists. It is widespread, frequent, and ecologically secure throughout ancient woodlands, managed oak forests, and commercial timber yards. Modern conservation forestry practices that encourage the retention of fallen deadwood and coarse woody debris in deciduous woodlands directly support thriving populations of this distinctive decomposer.
Interesting Factoid
The Black Bulgar fungus is made of tough, springy tissue that feels just like rubber shoe soles, and its Latin name ‘inquinans’ means ‘polluting’ because its black spores smudge off on your fingers like charcoal or permanent ink.