Leucocoprinus cretaceus

🏷️ Description

Leucocoprinus cretaceus, often referred to as the chalk white mushroom, is a fascinating species in the Agaricaceae family. Though fairly uncommon, it can be found gracing parks, gardens, and golf courses—particularly in warm, humid environments. This delicate mushroom has a distinctive white, wart-covered cap, a slender stem with a superior annulus, and a tendency to bruise yellow-brown to brown when handled.

🌱 Where Does It Grow? This mushroom thrives in warm and tropical regions, though it has been observed in greenhouses, potted plants, and planters worldwide. In colder climates, it struggles to survive outdoors but may persist in sheltered environments. As a saprotroph, it plays an essential role in breaking down decomposing organic matter, commonly appearing on wood chips, sawdust, compost heaps, and even tree bark.

🌍 A History of Misidentifications: Leucocoprinus cretaceus has been mistaken for similar species over the centuries. Early European mycologists often confused it with Leucocoprinus cepaestipes or Leucocoprinus birnbaumii, leading to taxonomic mix-ups:

• 1788: First described as Agaricus cretaceus by French botanist Jean Baptiste François Pierre Bulliard.

• 1801: Mycologist Christiaan Hendrik Persoon categorized it as a variant of Agaricus cepaestipes.

• 1821-1889: Various reclassifications under different genera like Coprinus, Lepiota, and Pratella.

• 1945: Officially classified as Leucocoprinus cretaceus by Marcel Locquin, yet confusion with other species persists even today.

🌳 Habitat & Distribution Leucocoprinus cretaceus enjoys a wide distribution in tropical and subtropical areas, with occurrences documented in South America, North America, Europe, and Asia. Greenhouses provide an ideal habitat in non-native regions, where it thrives in the warm, moist soil of potted plants.

📝 Notably, in 1907, American mycologist Andrew Price Morgan recorded this species flourishing in rich garden soil and hotbeds throughout North America. More recent studies have identified it in Paraguay and Argentina, further confirming its widespread presence.

🌎 What’s in a Name? The name cretaceus originates from the Latin word "creta", meaning chalk, aptly describing its pale, powdery appearance. Various common names across languages reinforce this idea, such as "Kreideweißer Champignon" in German, which translates to "chalk-white mushroom."

🍽️ Edibility & Safety Historically, some descriptions suggest that this mushroom was pleasant in taste and smell and even consumed. However, due to its similarity to other potentially toxic species, it is not recommended for foraging.

🔎 Identification

🍄 Cap: 0.79 to 3.54 inches (2 to 9 cm) wide. Starts bulbous or hemispherical, then expands to convex or nearly flat with age. The surface is stark white, adorned with woolly, wart-like scales, sometimes tinged brownish-yellow at the center. The margin is initially incurved, becoming decurved, often with remnants of the veil.

🌿 Gills: Free from the stem, crowded, thin, and white to very pale cream as they age.

📏 Stem: 1.18 to 4.33 inches (3 to 11 cm) long, 5–13 mm thick, tapering upwards from a swollen base (7–19 mm thick). White, covered in fine flocculose scales that may yellow with age. The surface is felty above the ring and warted below. A fragile, median ring is initially flared but becomes pendulous over time.

🥩 Flesh: White, unchanging when cut. Odor indistinct.

⚪ Spore Print: White to creamy white.

🦠 Spores: 6–12 x 4–7 μm, ellipsoid to subamygdaliform, smooth, with a small germ pore. Dextrinoid, congophilous, and cyanophilous. Thick-walled and slightly yellowish in KOH.

🔬 Microscopic Features: Basidia 4-spored (18–28 x 8.5–12 μm). Cheilocystidia 35–75 x 7.5–15 μm, widely cylindric to fusiform, occasionally with refractive encrustations. Pleurocystidia absent. Pileipellis consists of interwoven, hyaline to yellowish elements, some branching into letter-like shapes.

🏞️ Habitat & Distribution: Saprobic, often found in plant pots, greenhouses, and gardens. Prefers rich soil, wood debris, and compost. Widespread in tropical and subtropical regions, with occasional appearances in temperate zones. Documented in North America, South America, and worldwide where introduced.

🌍 Ecology: Grows alone, in groups, or loose clusters in cultivated and natural environments. Fruits year-round in suitable climates.

🎨 Unique Features

• Cap: Typically campanulate (bell-shaped) with fine scales and a striate margin.

• Color: Pure white, resembling chalk, sometimes with subtle tan hues at the center.

• Stem: Slender, hollow, and adorned with a partial veil that may form a ring.

• Bruising Reaction: Turns yellow-brown to brown when handled.

• Microscopic Characteristics: The cap’s hyphae have branched, fragmented projections, resembling stirred alphabet soup!

📜 Synonyms

• Agaricus cretaceus Bull. (1788)

• Agaricus cepistipes var. cretaceus Pers. (1801)

• Coprinus cepistipes var. cretaceus Gray (1821)

• Coprinus cepistipes ß cretaceus Gray (1821)

• Pluteus cretaceus Fr. (1836)

• Psalliota cretacea P.Kumm. (1871)

• Pratella cretacea Gillet (1878)

• Lepiota cepistipes var. cretacea Sacc (1887)

• Fungus cretaceus Kuntze (1898)

• Lepiota cretacea Mattir. (1918)

• Leucoagaricus cretaceus M.M.Moser (1953)

• Agaricus cretaceus var. ambiguus Fr. (1815)

• Psalliota cretacea f. grandis R.Schulz (1923)

• Lepiota cretata Locq. (1950)

• Leucocoprinus cretatus Locq. ex Lanzoni (1986)

Photo sources:

Photo 1 - Author: Denis Zabin (CC BY 4.0)

Photo 2 - Author: Siva Naturewild (CC BY 4.0)

Photo 3 - Author: Sindhu Haridas (CC BY 4.0)

Photo 4 - Author: Denis Zabin (CC BY 4.0)