Leucocoprinus fragilissimus

🏷️ Description

Meet Leucocoprinus fragilissimus, also called the fragile dapperling — a delicate and dainty yellow mushroom that seems almost too soft for this world! 💛 Often found in greenhouses or woodland debris, this puff of a mushroom is as beautiful as it is short-lived.

🧬 Taxonomy Tangle

This species has one of the most tangled naming histories in mycology 📜. First described in 1805 as Agaricus flammula, it went through a series of names and reclassifications — Lepiota, Pholiota, Hiatula, Mastocephalus — before finally landing in the Leucocoprinus genus, thanks to Patouillard (1900) and Pegler (1972).

The confusion arose from independent discoveries across Europe, Sri Lanka, and the Americas, especially in greenhouses filled with exotic tropical plants. With only old books, illustrations, and slow communication, many mycologists unknowingly described the same mushroom multiple times.

🔎 Identification

Leucocoprinus fragilissimus is a tiny, pale yellow dapperling that thrives on decaying plant matter like compost or humus. It grows alone or sparsely in woodlands, greenhouses, botanical gardens, and other humid environments — especially where tropical plants are present.

• Cap: 0.59 to 1.77 inches (1.5–4.5 cm), planoconvex to flat with a small central bump, deeply grooved, pale greenish-yellow fading to whitish with a yellow center.

• Gills: Free, distant, pale yellow, often dissolve in heat.

• Stem: 1.57 to 3.54 inches (4–9 cm) long, hair-thin (1–2 mm), fragile, pale yellow to white, with a thin, vanishing ring midway.

• Flesh: Insubstantial, yellowish; collapses quickly after maturing.

• Spores: White print; ellipsoid (9–12 × 7–8 µm) with a large apical pore; dextrinoid, hyaline in KOH.

• Odor: Indistinct.

• Habitat: Found across southeastern North America, Central & South America, southern Europe, Africa, Asia, Australia, and New Zealand, this mushroom is likely Pantropical in distribution. It often appears in summer and autumn, especially in hot, humid conditions.

• Microscopy: No pleurocystidia; clavate, collapsing cheilocystidia; cellular pileipellis.

👀 Look-Alikes

Confusion with other delicate mushrooms is common:

• Leucocoprinus magnicystidiosus – darker disc, larger cystidia

• Leucocoprinus flavescens – sturdier with smaller spores

• Bolbitius titubans – similar cap but different gill color

• Parasola spp. (Psathyrellaceae family) – similar cap form

📚 Historical Highlights

• 1867: Documented growing in tanbark in greenhouses in Ghent, Belgium 🌿

• 1871: Found in Sri Lanka near the Royal Botanical Gardens

• 1907: Observed in swampy areas of South Carolina, USA

• 1982: Helen Smith detailed it in Texas, comparing it with L. magnicystidiosus

📜 Synonyms

• Agaricus flammula Alb. & Schwein. (1805)

• Agaricus licmophorus Berkeley & Broome (1870)

• Hiatula fragilissima Ravenel (1853)

• Hiatula licmophora (Berkeley & Broome) Petch (1910)

• Lepiota flammula Gillet [1878]

• Lepiota fragilissima Morgan (1907)

• Lepiota licmophora (Berkeley & Broome) Saccardo (1887)

• Leucocoprinus licmophorus (Berkeley & Broome) Patouillard (1913)

• Mastocephalus licmophorus Kuntze (1891)

• Pholiota flammula Miq. (1912)

Photo sources:

Photo 1 - Author: Alan Rockefeller (CC BY-SA 4.0)

Photo 2 - Author: Jacqui Geux (CC BY 4.0)

Photo 3 - Author: Luis Carlos12 (CC BY 4.0)

Photo 4 - Author: Charlie Nadeau (CC BY-SA 4.0)