Leucocoprinus birnbaumii (plantpot dapperling)

Worldwide, in both natural and horticultural habitats.

Plantpot dapperling is a universally sulphur-yellow gilled mushroom that is easy to identify because of its bright colours and preferred habitat in houseplant pots, greenhouses and gardens.

The cap can be up to 7 cm across, but is usually smaller (2−4 cm). It is conical at first, but expands to become more or less flat; it can sometimes have a central knob or be indented. The surface is often finely roughened.

Underneath the cap, widely spaced yellow gills radiate from the centre. When mushrooms are young, the gills are covered by a thin yellow skin that stretches from the edge of the cap to the stalk, but this skin soon tears from the cap and can remain on the stalk like an inverted skirt. The stalk is up to 10 cm tall, but is typically shorter (5−7 cm) and slightly swollen at the base. The spores appear white in mass but are colourless and smooth under the microscope.

One variety (L. birnbaumii var. salvadorianus) has been recognised from Brazil, which differs in a scalier cap with a brick-coloured centre.

This species is easily recognised by its bright colour and habit of growing in pots and greenhouses worldwide. Its large range of spore sizes and numerous synonyms suggest there may actually be several species included under the name Leucocoprinus birnbaumii.

Plantpot dapperling is poisonous, but people and pets rarely try to eat it – it is possible its bright colour provides an instinctive warning. Its yellow pigments are due to chemicals called novel alkaloids, birnbaumins A and B. Although alkaloids are often toxic, it is not known if birnaumins are the active poisons in this mushroom.

Unexpectedly, Leucocoprinus birnbaumii is closely related to the preferred food of certain neotropical fungus-farming ants, which cultivate a closely related species. Did the ants choose to farm these fungi just because they are abundant in tropical soils, or because they are easy to cultivate in a variety of circumstances? Perhaps the adaptability of the plantpot dapperling to habitats around the world offers a clue. Their ability to thrive in artificial habitats is evidence of their adaptability to a wide variety of conditions.

This species occurs spontaneously in greenhouses and flowerpots throughout Kew.

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