Calocybe gambosa (St George’s mushroom)
St George's mushroom is one of the few good edible fungi to be found in spring, usually appearing in late April close to St George’s Day (23rd April), hence the popular name.
About this Species
St George’s mushroom is a distinctive species, one of the few larger fungi to appear regularly in spring. It is quite common in various grassy habitats and is a good edible fungus, recognised by the convex, whitish cap, the white, closely-spaced gills, and strong floury odour.
The fungus we refer to today as Calocybe gambosa has long been known and was first described by Linnaeus who, in his Species Plantarum published in 1753, named it Agaricus georgii, after St George. This name is not used today as the name Agaricus gambosus was applied by the great Swedish mycologist Elias Magnus Fries whose seminal work on fungi Systema Mycologicum, was published in 3 volumes from 1821-32. Names used by Fries take priority. The name Calocybe derives from the Greek kalos, meaning pretty, and cubos, head.
Geography & Distribution
Calocybe gambosa is widespread and found in temperate regions throughout much of Europe including parts of Russia, and Asia, including Korea and Japan.
Calocybe gambosa fruitbody (Image: © Malcolm Storey, 1999, www.bioimages.org.uk)
Calocybe gambosa has fleshy, whitish or pale tan fruitbodies and a mealy smell, and is quite distinctive. It fruits from spring to early summer (April to June) and is usually found growing in groups, sometimes forming fairy rings.
St George’s mushroom is unlikely to be confused with other species. However, some inedible or slightly poisonous Entoloma species appear in spring and can be similar, though these are usually browner or greyish and have pink gills when mature. They also lack the distinctive mealy odour of C. gambosa.
The cap of the fruitbody is whitish to cream or pale tan, convex, fleshy, smooth and 5 to 12 cm across. The margin of the cap is somewhat incurved (rolled under). The stipe (stalk) is central, cylindric, smooth and the same colour as the cap. The stipe is stout, 3 to 7 cm high and 1.5 to 3 cm thick. The gills are white or cream, sometimes with yellow-brown tints when older, closely spaced, with sinuate attachment (the gills shorten and curve back down the stipe a little before attaching). The spore deposit is white. The flesh has a strong, floury odour.
Calocybe gambosa was once thought to belong in the large genus Tricholoma, which similarly includes fleshy agarics with white spore deposit and sinuate gill attachment. However, true Tricholoma species are ectomycorrhizal (they grow in a mutually beneficial association with trees), whereas Calocybe species are saprotrophs (feeding on decaying organic matter).
Several other species were thought to belong to the genus Calocybe, some found in grassy places, others in woodlands. They mostly have smaller fruitbodies than C. gambosa, and some of the commoner ones have attractive pink or purple colours, but they are not necessarily edible. However, recent work has shown that these species are better placed in other genera, including Tricholomella and Rugosomyces.
Only one other British species is now placed in Calocybe, the very rare but attractive C. favrei, which occurs in woodlands on calcareous soil. It differs from C. gambosa in having blue-grey fruitbodies with bright yellow gills.
Threats & Conservation
No specific threats are known and the species is not currently considered as of conservation concern. However, it is commercially collected in some areas and the effects of this on populations of the fungus are little known.
- Culinary delicacy
- Antibacterial properties
- Reduces blood sugar levels
- Pest control
This is an excellent edible fungus, sought-after as a culinary delicacy throughout its range. It has also been reported to have important medicinal properties including antibacterial activity. A dichloromethane compound extracted from this species has been reported to be active against some bacteria, including Escherichia coli. However, antibacterial properties have not been confirmed in other studies. The species has also been reported to reduce blood sugar levels. A substance called phenoxazone, which can be used in the pest control of nematode worms, has been isolated from the St George’s mushroom.
St George's mushroom at Kew
Calocybe gambosa is frequent in the Gardens wherever suitable habitat occurs (for example grassy places and woodland edge).
Preserved specimens of Calocybe gambosa from throughout its range are maintained in the Kew Mycology Herbarium and, although not accessible to the general public, are available for study by research workers worldwide.
Keep up to date with events and news from Kew
The flowering parts of these popular houseplants can resemble the body and twisted neck of a flamingo.
- newly discovered
- around the world
- of use
- ground breaking
- garden plants
- english garden
Plants & Fungi blogs from Kew
25 Jan 2013
He may be a Seed Morphologist but Wolfgang Stuppy of Kew's Millennium Seed Bank discovers there is more to the snake gourd than just some strange fruit and eccentric seeds.