Arrhenia chlorocyanea
🏷️ Description
Meet Arrhenia chlorocyanea, affectionately known as the verdigris navel — a rare and striking mushroom with deep 🔵 blue-green hues that shimmer like oxidized copper. Though small in size, this fungus turns heads in mossy woods and open fields, particularly in Europe and North America. Whether you’re a seasoned mycophile or a curious nature wanderer, this mysterious mushroom is worth a closer look.
🧠 Taxonomy & Naming Confusion
Originally described as Agaricus chlorocyaneus in 1885, this species has been taxonomically bounced around: from Omphalina to Clitocybe atroviridis, and finally placed in Arrhenia in 2002 by Redhead, Lutzoni, Moncalvo, and Vilgalys. Its naming history is tangled with debates over clamp connections, look-alike species, and lost type specimens — a true detective tale for taxonomists!
🎨 Color Morphs & Regional Variants
While often a deep green, some specimens—especially from California—display a navy or steel-blue tone. The cap may be smooth, wrinkled, or even slightly furfuraceous (bran-like), and changes color as it dries due to its hygrophanous nature. The margin becomes lined (striate) as it ages.
🔎 Identification
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Cap: 0.39 to 0.98 inches (1 to 2.5 cm), dark green to steel-blue, depressed center, striate margin, hygrophanous
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Gills: Decurrent, distant, pale greenish to blue-gray, often forked
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Stem: 0.79 to 1.57 inches (2 to 4 cm) tall, 0.08 to 0.12 inches (0.2 to 0.3 cm) thick, concolorous with cap or darker
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Flesh: Thin, watery, grayish-blue to greenish
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Spore Print: White
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Spores: Smooth, ellipsoidal to oboval, (7–11 × 4.5–6 µm), inamyloid
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Smell & Taste: Earthy to slightly fishy smell, mild taste
🧬 Microscopic Features
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Spores: Elliptic to cylindrical, (7–11 × 4.5–6 µm), smooth, inamyloid
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Basidia: Mostly 4-spored (23–31 × 6–8.5 µm)
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Clamp connections: Present
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Cystidia: Typically absent
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Hyphal structure: Cap and stem tissue ranges from colorless to greenish in KOH, with some encrusting pigments and cystidioid end cells
🌱 Ecology & Habitat
This saprobic mushroom thrives in:
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Mossy patches, often with lichens
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Sandy, nutrient-poor soil
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Open meadows, ditches, forest edges
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Coniferous woods (in Europe)
Found gregariously or scattered, usually during the cooler months — from late fall to early spring (November–May), with some sightings in summer to autumn in European reserves.
👀 Look-Alikes
1️⃣ Entoloma incarnatofuscescens: Similar shape but pink spore print
2️⃣ Clitocybe odora: Has a strong anise scent
3️⃣ Omphalina ericetorum var. viridis: Lacks clamp connections
4️⃣ Chrysomphalina grossula: A misidentified similar species in some collections
📉 Conservation & Rarity
The verdigris navel is considered rare in parts of Germany, British Columbia, and elsewhere. Its small size, seasonal appearance, and specific habitat preferences make it a hidden gem for keen-eyed foragers and photographers.
📜 Synonyms
Agaricus chlorocyaneus Patouillard (1885)
Agaricus ericetorum var. viridis Hornemann
Agaricus umbellifer var. viridis Hornem. (1819)
Agaricus umbelliferus var. b chalybaeusNiessl (1865), Verhandlungen des naturforschenden vereines in Brünn, 3, p. 123
Omphalia chlorocyanea (Patouillard) Saccardo (1887), Sylloge fungorum omnium hucusque cognitorum, 5, p. 336
Omphalia umbellifera f. viridis (Hornem.) Cejp (1936)
Omphalia umbellifera var. viridis (Hornemann) Costantin & L.M. Dufour (1891), Nouvelle flore des champignons, Edn 1, p. 39
Omphalia viridis (Hornemann) J.E. Lange (1930), Dansk botanisk arkiv, 6(5), p. 12 (nom. illegit.)
Omphalina chlorocyanea (Patouillard) Singer (1951) [1949], Lilloa, 22, p. 212
Omphalina umbellifera var. viridis (Hornemann) Quélet (1886), Enchiridion fungorum in Europa media et praesertim in Gallia vigentium, p. 44
Omphalina viridis (Hornemann) Kuyper (1984), Persoonia, 12(2), p. 188
Photo sources:
Photo 1 - Author: Tannar Coolhaas (CC BY 4.0)
Photo 2 - Author: Sam (Public Domain)
Photo 3 - Author: Ken-ichi Ueda (Public Domain)
Photo 4 - Author: Reagan peschke (CC BY 4.0)
