Sarah Brown
Earthstar mushrooms are fungi that grow on decaying organic matter and play an important role in breaking down tough materials and returning nutrients to the soil. They are known for their distinctive appearance, which consists of a roundish ball at the centre and starlike rays extending outwards. While some earthstar species are common in certain regions, others are considered rare. For example, the daisy earthstar is a rare species in Britain, while the collared earthstar is the most widespread species in the UK. Earthstars were used medicinally by indigenous peoples of the Americas and are still used in traditional Chinese medicine.
| Characteristics | Values |
|---|---|
| Common names | Hygroscopic earthstar, barometer earthstar, false earthstar, water-measure earthstar, hygrometer earthstar, Astraeus earthstar |
| Scientific name | Astraeus hygrometricus |
| Habitat | Southern Europe, Asia, North America |
| Appearance | Roundish ball in the center of starlike rays; displays the characteristic earthstar shape that is a result of the outer layer of fruit body tissue splitting open in a star-like manner |
| Size | Ball width: up to 1.5 inches; ray length: 0.5–2 inches; spore sac diameter: up to 5 cm |
| Colour | Greyish brown |
| Spores | Round, warted, spherical, 3.5–4.5 μm in diameter |
| Edibility | Not edible in North America and the UK; edible in Thailand and immature forms in other regions |
| Medicinal uses | Used by indigenous peoples of the Americas, traditional Chinese medicine |
| Rarity | Some species previously considered rare are now found in habitats with wood chips, such as Kew Gardens |
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What You'll Learn
- Astraeus hygrometricus, commonly known as the false earthstar, is a species of fungus found in Southern Europe
- Astraeus earthstars are a valuable wild mushroom in Thailand, but they are not eaten in North America
- Earthstars are inedible and some are poisonous. They are sometimes called 'stomach fungi'
- Earthstars are saprobic fungi that break down tough organic materials, returning nutrients to the soil
- The indigenous peoples of the Americas used earthstars medicinally
Astraeus hygrometricus, commonly known as the false earthstar, is a species of fungus found in Southern Europe
False earthstar is an ectomycorrhizal species, meaning it grows in association with various trees, particularly in sandy or clay soils with oak, pine, or mixed hardwood trees. It is often found in areas with rich soil and adequate moisture, such as along streams, rivers, and woodland edges. The mutualistic relationship between tree roots and the mycelium of the fungus helps the trees extract nutrients, especially phosphorus, from the soil, while the fungus receives carbohydrates from photosynthesis in return.
False earthstar is native to Southern Europe, ranging from Southern France to Turkey. It was historically believed to have a cosmopolitan distribution, but recent research suggests its range is more limited. The species was first described by Christiaan Hendrik Persoon in 1801, who classified it as Geastrum hygrometricus. However, in 1885, Andrew P. Morgan proposed that it should be placed in a new genus, Astraeus, due to several microscopic differences from the Geastrum genus.
The common names of the false earthstar refer to its hygroscopic nature, as it can open and close its rays in response to changes in humidity. This behaviour protects the spores from predation in dry conditions and aids in dispersal when humidity is high. While it is generally considered inedible, the false earthstar is consumed in some parts of South and Southeast Asia.
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Astraeus earthstars are a valuable wild mushroom in Thailand, but they are not eaten in North America
Astraeus earthstars, also known as false earthstars, are a valuable wild mushroom in Thailand, where they are picked and sold fresh or canned. However, they are not commonly consumed in North America, and there are concerns about their edibility.
False earthstars are characterised by their star-like shape, with a round central spore sac surrounded by a star-shaped outer layer that splits open as the fungus matures. This outer layer is thick and leathery, with a rough, earth-coloured exterior that helps the fungus camouflage into the forest floor. The inner spore sac is typically grey-brown and has multiple holes, giving it the name "saltshaker earthstar". The Astraeus species is part of the Boletales family and is not closely related to the true earth stars of the Geastrum genus, although they have often been confused due to their similar appearance.
In Thailand, Astraeus earthstars are specifically identified as either A. asiaticus or A. odoratus, which are now considered distinct from A. hygrometricus, the original name given to the species. A. asiaticus and A. odoratus were first identified as unique species in the 2000s through phylogenetic analyses of Asian Astraeus populations.
In North America, Astraeus earthstars have been classified into three species: A. pteridis, found in the central to southern US and Mexico; A. morganii, found in the southern US; and A. smithii, found in the northern to central US. These species are believed to be genetically and ecologically distinct from their Asian counterparts, and their edibility is uncertain. While some North American sources list A. hygrometricus as inedible due to its toughness, the species is regularly consumed in Nepal, South Bengal, India, and Japan.
The difference in edibility between Astraeus earthstars in Thailand and North America may be attributed to regional variations in the species. Additionally, the cooking methods and cultural practices associated with preparing and consuming wild mushrooms may vary between the two regions.
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Earthstars are inedible and some are poisonous. They are sometimes called 'stomach fungi'
Earthstars are inedible and some are even poisonous. They are sometimes called stomach fungi. Earthstars are a type of fungus that resembles a roundish ball in the center of starlike rays. They grow on the ground in open woods, usually in sandy soils, and are saprobic, meaning they live on decaying organic materials.
There are several different species of earthstars, including the false earthstar (Astraeus hygrometricus), which is common in temperate and tropical regions, and the collared earthstar (Geastrum triplex), which is the largest member of the genus Geastrum or earthstar fungi. The false earthstar was previously thought to have a cosmopolitan distribution, but it is now believed to be restricted to Southern Europe. The collared earthstar can be found in the detritus and leaf litter of hardwood forests around the world and can reach a tip-to-tip length of up to 12 centimeters.
The edibility of earthstars varies depending on the species and regional differences. For example, Astraeus hygrometricus is considered a valuable wild mushroom in Thailand and is picked and sold fresh or canned. However, the same species in North America is not known to be used for cooking. The fruit bodies of Geastrum triplex are non-poisonous but are tough and fibrous, leading to them being considered of "no alimentary interest". Mycologist David Arora notes that they are reputed to be edible when immature, but they are rarely found in this form.
Despite their inedibility or potential toxicity, earthstars have been used medicinally by indigenous peoples of the Americas, such as the Blackfoot and Cherokee, and in traditional Chinese medicine to reduce inflammation in the respiratory tract and to stanch bleeding and reduce swelling.
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Earthstars are saprobic fungi that break down tough organic materials, returning nutrients to the soil
Earthstars are a type of fungus that are characterised by their star-like shape. They are commonly found in open woods, growing on the forest floor, and are known to be inedible and sometimes poisonous.
There are over 15 species of earthstar native to Britain, including the daisy earthstar, which is considered a relatively rare species in the UK, and the crowned earthstar, which is widespread but scarce in Britain, found mostly in the east. The most widespread species is the collared earthstar, which can be found in Thetford Forest, Norfolk, and has a diameter between seven and ten centimetres. The sessile earthstar, which has a diameter of only two centimetres, is more common in England than in other parts of the UK.
Earthstars are saprobic fungi, meaning they break down tough organic materials and return nutrients to the soil. They are similar to mushrooms in that they form part of the kingdom Fungi, but they lack chlorophyll and must take nutrients from other materials.
The Astraeus genus of earthstar fungi has been found to have distinct genetic differences between populations in Asia, North America, and Europe. Astraeus hygrometricus, commonly known as the hygroscopic earthstar, was previously thought to have a cosmopolitan distribution, but it is now believed to be restricted to Southern Europe. This species is hygroscopic, meaning it can open up its rays to expose the spore sac in response to increased humidity and then close them again in drier conditions.
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The indigenous peoples of the Americas used earthstars medicinally
Earthstar mushrooms are characterised by a roundish ball at the centre of star-like rays. They grow on the floor of open woods, usually in sandy soils. They are neither plants nor animals, but belong to the kingdom of fungi.
Indigenous communities in the Americas have made several other contributions to medicine. For instance, the Iroquois and Seneca tribes invented baby bottles and baby formula, which are important for infant health when breast milk is unavailable. The concept of inoculation also existed among Native Americans, who would ingest small amounts of harmful substances to build immunity against their toxic effects. They also chewed willow bark to soothe aches and pains. The active ingredient in the bark, salicin, was later found to be the basis of aspirin. Furthermore, cedar, which is used in sweat lodges and for purifying homes, has antibiotic and anti-inflammatory properties when made into a tea. Sweetgrass, another sacred plant, is used to treat coughs, sore throats, and fever when made into a herbal tea. Its essential oil is also used in foods and alcoholic beverages.
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Frequently asked questions
Earthstar mushrooms are not rare overall, but some species are rarer than others. The daisy earthstar, for example, is a relatively rare species in Britain.
Earthstar mushrooms can be found in hardwood forests around the world, in sandy soils, and on the ground in open woods. They grow on the floor of open woods, singly or in groups. They are also found in mature herbaceous borders that have been mulched with wood chips.
Earthstar mushrooms are roundish balls with starlike rays. They are usually grey-brown in colour. The spores are round and covered with small, spiny warts.
Earthstar mushrooms are not edible and some are even poisonous. However, they are used medicinally by indigenous peoples of the Americas.
