Yellow Earthballs (Scleroderma sinnamariense)
Yellow Earthballs (Scleroderma sinnamariense)
Yellow Earthball (Scleroderma sinnamariense) is a stemless, lemon-yellow ball fungus of tropical forests in Africa, Asia and South America, living joined to the roots of host plants. It has no gills and no stem, and the inside ripens from solid white to a dark brown dust of spores. It is treated as poisonous, yet it is still gathered and eaten young in parts of Indonesia, where earthball poisonings have killed people.
Scleroderma sinnamariense Mont. — Sclerodermataceae — Boletales
The Yellow Earthball (Scleroderma sinnamariense) is a tropical puffball-shaped fungus with a thick, leathery, chrome-yellow skin and no stem, described from French Guiana in 1840 and now known mostly from Southeast Asia. It is an ectomycorrhizal fungus, meaning it wraps the fine roots of a living host plant in a sheath of fungal tissue and trades mineral nutrients for sugar. Its best documented partner is not a tree at all. It is Gnetum, an unusual group of tropical vines and shrubs that sit outside the flowering plants entirely.
One point needs settling before anything else. The name "yellow earthball" is also used in Europe and North America for Scleroderma citrinum, a temperate species of heaths and oak woods that dominates English-language earthball content. That is a different fungus with different hosts, a different climate, and its own separate poisoning literature. Everything on this page refers to Scleroderma sinnamariense, the tropical species.
What Is the Yellow Earthball (Scleroderma sinnamariense)?
Earthballs look like puffballs and are not closely related to them. Scleroderma belongs to the Boletales, the order that contains boletes, so the Yellow Earthball (Scleroderma sinnamariense) is a closer relative of a porcini than of a giant puffball. The resemblance to a puffball comes from a shared strategy rather than shared ancestry, since both give up gills and a stem in favour of a sealed bag that ripens internally and releases dry spores when it splits.
The fruiting body is a rounded ball, usually sitting directly on the ground or on rotten wood, anchored by a cord of tissue at the base. The outer skin is thick and tough, coloured lemon to chrome yellow, and scattered with small dark brown scales. Cut one open when young and the interior is solid white. As it matures the interior darkens to brown and finally becomes powder.
What separates the Yellow Earthball (Scleroderma sinnamariense) from most fungi sold as cultures is that it cannot feed itself on dead material alone in any reliable way. It is a symbiont. In Cameroon, plants in the genus Gnetum were found to be almost always ectomycorrhizal, and the dominant fungal partner across farmland, cocoa plantations, fallows and undisturbed forest was this species. Its yellow root sheath was the most widespread and most prevalent of only two partner types recorded across the whole survey.
That relationship makes the species interesting to researchers and awkward for growers. A fungus that lives on a host root does not fruit in a bag of sterilised grain, no matter how the bag is treated. It also makes the Yellow Earthball (Scleroderma sinnamariense) one of the few earthballs with a documented, repeatable inoculation method for producing colonised plants.
The species was named for Sinnamary, a river and commune in French Guiana, and its type specimen was collected there in the Amazon basin. Almost every modern record comes from the opposite side of the planet. Malaysia and Thailand alone account for more than half of all occurrence records, and no sequence has ever been tied back to the original French Guianan material.
Interested in this species? Out-Grow carries a liquid culture.
Yellow Earthball (Scleroderma sinnamariense) Liquid CultureHow Is the Yellow Earthball (Scleroderma sinnamariense) Classified?
Scleroderma sinnamariense Mont. was published in Annales des Sciences Naturelles, Botanique, series 2, volume 14, page 331, in 1840. The type collection is Leprieur 386, and the original record gives the substrate and locality as rotten wood in French Guiana. The name is listed as legitimate with no accepted synonyms in Index Fungorum, MycoBank and GBIF, which is unusually clean for a fungus of this age.
| Rank | Classification |
|---|---|
| Kingdom | Fungi |
| Phylum | Basidiomycota |
| Class | Agaricomycetes |
| Order | Boletales |
| Suborder | Sclerodermatineae |
| Family | Sclerodermataceae |
| Genus | Scleroderma |
| Species | Scleroderma sinnamariense Mont. (1840) |
| MycoBank / Index Fungorum | 185045 |
| NCBI Taxonomy ID | 150802 |
| GBIF ID | 5239987 |
Yellow Earthball (Scleroderma sinnamariense) sectional placement and why it changed
Guzmán divided Scleroderma into three sections using two characters, the ornamentation of the spore surface and the presence or absence of clamp connections, which are small bridging structures on the hyphae. Section Aculeatispora held species with spiny spores and no clamps. Section Sclerangium held species with partly netted spores. Section Scleroderma held species with fully netted spores and clamps.
In 2000, Guzmán and Ovrebo moved this species out of section Sclerangium and into section Scleroderma, on the grounds that its spores carry a well developed net. The 2013 emendation of the genus then complicated the label rather than the placement. Because S. verrucosum became the genus type, the netted-spore section was renamed section Reticulatae, and Aculeatispora was sunk into section Scleroderma. Older and newer section names for the Yellow Earthball (Scleroderma sinnamariense) are therefore not interchangeable, and papers on either side of 2013 need reading with that in mind.
Yellow Earthball (Scleroderma sinnamariense) misapplied names and identification traps
Two long-running misapplications sit in the literature, and both matter to anyone trying to trace records or source material.
Mexican records of this species from 1983, 2003 and 2011 are now attributed to confusion with S. bermudense, and the 2013 revision concluded that the species seems absent from Mexico. Despite that, a 2026 global checklist still tabulates Mexico for the species while citing the very paper that removed it. Older keys also record a misapplied concept, S. sinnamariense sensu Guzmán 1970, which is again S. bermudense.
The error also runs the other way. African material published as S. bovista by Dissing and Lange in 1962 is now referred to this species. So the African record is larger than the literature makes it look, and the Mexican record is smaller.
Scale check for the genus. A 2025 review counted 206 published Scleroderma names resolving to 76 accepted species, while popular field keys still describe the genus as holding "about 25 species." Any identification made from a general field guide is being made against a third of the real genus.
How Do You Identify the Yellow Earthball (Scleroderma sinnamariense)?
The most precise modern description comes from the sequenced Thai strain CMUS01, collected in Doi Suthep-Pui National Park near Chiang Mai in July 2010. It is the reference point for the figures below, and it is also the strain behind almost all of the published culture physiology.
Yellow Earthball (Scleroderma sinnamariense) measurement conflicts in the literature
Published measurements for this species do not agree, and a guide that hides that is not being useful. The Thai reference strain gives spores of 4.18 to 6.15 micrometres. A Thai regional review and an Amazonian revision both give 7 to 9 micrometres, close to double the volume. The same two sources also disagree on fruiting body size, at 21 to 64 millimetres against 8 to 10 centimetres.
Spore ornamentation is contested in the same way. The 2000 transfer between sections rested on a well developed net on the spore surface. The Amazonian revision describes the spores as echinulate, meaning covered in short spines with no net at all. Since the sectional placement was built on that character, the disagreement is not cosmetic.
The most plausible reading is that material from Amazonia and material from Southeast Asia are not the same biological entity, and that the name currently covers a species complex. No epitype has been designated and no sequence has been tied to the 1840 French Guianan type, so nothing can be resolved yet. Treat any single published measurement as describing one population rather than the species.
Yellow Earthball (Scleroderma sinnamariense) lookalikes and how to separate them
Scleroderma xanthochroum
The sister species, described from Peninsular Malaysia and overlapping in range. It has netted spores. This is the hardest separation in the group and effectively needs sequencing rather than a hand lens.
Scleroderma citrinum
The temperate "common earthball," also called yellow earthball in Europe. Coarsely warted rather than scaly, ochre rather than chrome yellow, and found with oak and birch on heaths. Poisonous, and the source of most earthball content online.
Scleroderma yunnanense
Spiny rather than netted spores, a much thicker skin at 2 to 7 mm, smaller fruiting bodies at 2.5 to 5 cm, and a light reddish reaction to potassium hydroxide solution.
Scleroderma bermudense
The species behind the discredited Mexican records. Any Neotropical collection labelled S. sinnamariense from Mexico should be assumed to be this until sequenced.
Scleroderma camassuense
Separated on microscopy. This species has pilocystidia, which are projecting cells in the outer skin layer, and S. camassuense does not.
True puffballs (Lycoperdon, Calvatia)
Thin, soft, papery skin instead of a thick leathery one, and an interior that never passes through a firm dark stage. The confusion runs one way and is dangerous, since several puffballs are edible and earthballs are not.
Field note on skin thickness. Herbarium keys usually measure the skin of dried material, which is markedly thinner than fresh. A collection keyed against dried-material figures while still fresh will run out at the wrong species.
Where Does the Yellow Earthball (Scleroderma sinnamariense) Grow?
GBIF holds 227 occurrence records for the Yellow Earthball (Scleroderma sinnamariense), and they are heavily weighted towards Southeast Asia. Malaysia and Thailand together supply more than half. The Amazonian type locality contributes a small handful, and a scatter of African, Pacific and East Asian records fills out the rest.
| Region | Countries and record counts |
|---|---|
| Southeast Asia | Malaysia 83, Thailand 35, Singapore 8, Vietnam 8, Philippines 7, Laos 4, Indonesia 3, Brunei 2, Cambodia 1, Myanmar 1 |
| Neotropics | French Guiana 12, Guyana 7, Brazil 5, Costa Rica 2, Ecuador 1 |
| Africa | DR Congo 6, Cameroon 2, Burkina Faso 1, Republic of Congo 1, Kenya 1 |
| East and South Asia | China 5, Japan 3, India 2, Nepal 1, South Korea 1 |
| Oceania | Papua New Guinea 4, Fiji 3, Solomon Islands 2, Australia 1 |
A 2026 global checklist lists the species from only eight countries and records no host and no confirmed ectomycorrhizal activity for it. That is a substantial undercount against both the occurrence data above and the Cameroonian root-tip work, and it is worth knowing if you are citing that review as a source.
Yellow Earthball (Scleroderma sinnamariense) and its Gnetum host partnership
The central ecological fact about this species is its association with Gnetum. Gnetum is a gnetophyte, a small group of tropical vines, shrubs and trees that are neither conifers nor flowering plants. In Cameroon, Gnetum species were found to be almost always ectomycorrhizal with just two fungal partner types, and the yellow one was identified as this species by both morphology and DNA. Structures from arbuscular mycorrhizal fungi, the more common soil symbionts, were absent.
Colonisation rates tracked habitat quality closely. Roots in mature closed forest were 54 to 66 percent colonised. Fallow land ran at 34 to 54 percent. Secondary forest was lowest at 15 to 33 percent. Propagules of the fungus were nonetheless present across farmland, cocoa plantations, Chromolaena fallows and undisturbed forest, so the fungus survives disturbance even where colonisation falls.
In Costa Rica the same partnership appears with a different plant. The fungus is described as critical to Gnetum leyboldii, a strictly ectomycorrhizal climber, in lowland wet forest at La Selva receiving over 4,000 millimetres of rain a year. The Neotropical and African populations are therefore doing the same ecological job on two continents.
Yellow Earthball (Scleroderma sinnamariense) habitat, other hosts and trophic mode
Thai records place the species on sandy soils in pine forest, with no pine species named, and give host families including Caesalpiniaceae, Dipterocarpaceae and Phyllanthaceae. A broader host list for the genus adds Fagaceae, Myrtaceae and Pinaceae. Away from Gnetum, host data for this species thins out quickly.
West African surveys are a useful negative result. Studies in Senegal and the Fouta Djalon highlands of Guinea sampled the roots of Afzelia, Uapaca and Anthonotha and recovered S. verrucosum, S. dictyosporum and S. cepa. They did not recover this species. Its African host range is currently defined by Gnetum and little else.
One complication remains open. The 1840 protologue records the type as growing on rotten wood, and a genus monograph notes that symbiotic status is proven for some Scleroderma and only inferred for others, with several apparently capable of living as free-standing decomposers. The Yellow Earthball (Scleroderma sinnamariense) is a confirmed root symbiont, but whether it is exclusively so has not been demonstrated.
No conservation assessment exists for this species. That is unremarkable, since only around 1,300 fungi appear on the IUCN Red List against more than 169,000 assessed organisms overall.
Can You Cultivate the Yellow Earthball (Scleroderma sinnamariense)?
The honest answer needs stating plainly. You cannot fruit the Yellow Earthball (Scleroderma sinnamariense) on sterile substrate. There is no published protocol for fruiting it on grain, on bulk substrate, or in any axenic system, and none is likely, because the fruiting body forms only where the fungus is joined to a living host root. Its mycelium is straightforward to culture. Its fruiting bodies are not a cultivation product.
Live cultures of this species do circulate in the hobby market with no protocol and no provenance data attached. Any listing implying that a culture of this species will produce earthballs in a grow bag is selling an outcome that has never been achieved by anyone.
Yellow Earthball (Scleroderma sinnamariense) culture media and growth conditions
Pure culture has been established two ways. The first takes tissue from inside a fresh fruiting body and plates it onto modified Melin-Norkrans agar, a standard medium for root-symbiotic fungi, at 30 degrees Celsius in the dark. The second isolates directly from colonised root tips of Gnetum africanum. Both work, and the second matters because it means a culture can be recovered without a fruiting body.
Across ten media tested at pH 6.0 and 30 degrees Celsius for three weeks, the ranking was clear. Fungal host agar gave the best growth at 43.5 millimetres of colony and 14.27 milligrams of dry biomass. Modified MS medium came second and modified Melin-Norkrans third. The weakest colony was on glucose-modified Melin-Norkrans at 15.10 millimetres, and the lowest biomass was on modified Schenk-Hildebrandt at 2.60 milligrams. Colonies were yellow on every medium tested, and clamp connections were visible throughout.
A separate line of work used Melin-Norkrans variants adjusted to pH 5.5 before autoclaving, with a carbon to nitrogen ratio near 20 to 1 and 50 millimolar MES buffer to hold the pH steady. Colony diameters there ran from 5 to 71 millimetres by day 23, which brackets the figures above and suggests strain and medium both matter more than either alone.
Yellow Earthball (Scleroderma sinnamariense) nitrogen preferences in liquid culture
This species has been characterised in liquid culture more carefully than most symbiotic fungi, which is directly useful for anyone formulating a broth. Grown in liquid Melin-Norkrans at 30 degrees Celsius in the dark at a carbon to nitrogen ratio of 20 to 1, thirty-day mycelial dry weights sorted the nitrogen sources into a clear order.
| Nitrogen source | Mycelial dry weight at 30 days |
|---|---|
| Peptone | 16.7 ± 1.4 mg |
| Arginine | 12.9 ± 1.9 mg |
| Alanine | 11.2 ± 0.6 mg |
| Glutamic acid | 8.8 ± 1.2 mg |
| Ammonium sulphate | 7.2 ± 1.1 mg |
| Calcium nitrate | 4.2 ± 0.1 mg |
| Bovine serum albumin | 3.5 ± 0.2 mg |
| Glycine | 2.8 ± 0.5 mg |
| No nitrogen | 2.5 ± 0.1 mg |
The pattern names the fungus twice over. It is a peptone fungus, meaning it grows best on partly broken-down protein rather than on simple mineral nitrogen. It is also a non-protein fungus, since intact bovine serum albumin performed barely better than no nitrogen at all. It can use protein that something else has already started digesting, and it cannot attack whole protein itself.
Yellow Earthball (Scleroderma sinnamariense) contamination risks and handling
Two features of this fungus make clean work harder than usual. Growth is slow, with the best solid-media result reaching only about 43.5 millimetres in three weeks, so any contaminant has a long head start. The optimum temperature of 30 degrees Celsius also sits in the band that favours Trichoderma and most bacteria, so the incubation conditions that suit the fungus suit its competitors equally well.
There is one useful lever. This species grows across the full range from pH 2.0 to 9.0, which very few contaminants tolerate. Acidifying the medium costs some growth rate and removes most bacterial competition. Peptone-rich broth gives the highest biomass but also the highest bacterial risk, so the two decisions are linked and should be made together.
Yellow Earthball (Scleroderma sinnamariense) host inoculation, the only fruiting-capable route
Inoculating a living host is the only pathway that has ever produced a functioning system with this fungus, and it has been done successfully more than once.
Work on rooted cuttings of Gnetum africanum produced inoculum on peat and vermiculite, barley, rye grain, baby corn and nitrocellulose filter paper. All carriers supported growth, although Paxillus and Pisolithus grew better on them than this species did. Viable root tips, mycelium and spores all produced ectomycorrhizas on previously uncolonised plants, and both fresh and dried fruiting bodies worked as inoculum.
An Indonesian trial on Gnetum gnemon, the melinjo tree, tested seven-month-old seedlings with root pruning at 0, 30 and 50 percent crossed against three inoculum treatments over four months. Infection was zero percent in every control and reached up to 100 percent in inoculated plants, with root colonisation between 7.78 and 62.11 percent and visible ectomycorrhizas by three months. The root sheath formed by this species was distinctly yellow, against a white sheath from the comparison Scleroderma, with monopodial branching and clamp connections in the sheath itself.
One result from that trial is worth holding onto. Height, stem diameter and biomass did not differ significantly between treatments over the four months. Colonisation was achieved, but a growth benefit was not demonstrated inside that window. Related nursery work with congeners sets similar expectations, with spore inoculation of Afzelia africana reaching 21.5 to 26.4 percent mycorrhization against zero in controls, and modest height gains after five months.
Choose a compatible host
Gnetum is the documented partner, with G. africanum and G. gnemon both confirmed. Without a living ectomycorrhizal host there is no pathway forward.
Expand the culture
Grow the liquid culture at 30 °C in the dark near pH 5.0. Peptone-based nitrogen gives the highest biomass. Expect slow growth and check often.
Prepare a carrier
Peat and vermiculite, barley, rye grain or baby corn have all carried this fungus. The carrier is a delivery vehicle for the roots, not a fruiting substrate.
Inoculate uncolonised seedlings
Use plants with no prior colonisation, since controls in the melinjo trial stayed at zero percent infection while inoculated plants reached 100 percent.
Hold tropical conditions
This fungus fails permanently above 35 °C and does not recover. Keep the root zone warm and stable rather than hot.
Verify at three months
Look for the yellow root sheath under a hand lens. That colour separates this species from the white-sheathed Scleroderma partners.
What a Yellow Earthball (Scleroderma sinnamariense) liquid culture is actually for
This culture is research and experimental material, not a route to fruiting bodies. It suits seedling and cutting inoculation of compatible Gnetum hosts, ectomycorrhizal physiology work, phosphate and heavy-metal solubilisation assays, auxin and siderophore studies, and mycelial biomass for pigment chemistry. The published growth parameters are unusually complete for a symbiotic fungus, which makes this species a practical teaching and laboratory organism. Anyone expecting earthballs from a sterile substrate should look at a saprotrophic species instead.
What Bioactive Compounds Does the Yellow Earthball (Scleroderma sinnamariense) Contain?
Chemistry for this species is thin but specific. Two pigments have been isolated from its fruiting bodies, methyl 4,4′-dimethoxyvulpinate and 4,4′-dimethoxyvulpinic acid, reported in Natural Product Communications in 2011. The methanol extract, its fractions and the isolated acid showed moderate inhibition of some pathogenic test organisms, although the published abstract names neither the organisms nor the values.
Both compounds are pulvinic acid derivatives. Pulvinic acids are a pigment family typical of the Boletales, and they are what makes this fungus yellow. A 1996 survey found pulvinic acid derivatives across the genus, and pigments recorded from other Scleroderma species include xerocomic acid, badione A, norbadione A and sclerocitrin.
Methyl 4,4′-dimethoxyvulpinate
Isolated from fruiting bodies of this species. A pulvinic-type yellow pigment. Bioactivity reported only as moderate antimicrobial inhibition, with no organisms or values published.
4,4′-dimethoxyvulpinic acid
The second pigment isolated from this species, tested alongside the crude methanol extract and its fractions. Same evidence limitation applies.
Sclerocitrin and chalcitrin
Pulvinic acid dimers first isolated from the genus in 2004. Named in review literature as a candidate earthball toxin, though not chemically confirmed from this species.
Norbadione A and badione A
Genus-level pigments in the same structural family, reported with antioxidant and immunomodulatory activity. Not isolated from this species specifically.
Evidence quality, stated plainly. Every bioactivity figure below the two named pigments comes from other Scleroderma species. A methanol extract of S. citrinum gave an IC₅₀ of 15 micrograms per millilitre against herpes simplex virus type 1 and a minimum inhibitory concentration of 100 micrograms per millilitre against Mycobacterium tuberculosis H37Ra, both in vitro only. No animal study and no human trial exists for this species or for the genus. No quantified bioactivity data specific to the Yellow Earthball (Scleroderma sinnamariense) is available beyond the word "moderate."
Is the Yellow Earthball (Scleroderma sinnamariense) Safe to Eat?
No. Treat the Yellow Earthball (Scleroderma sinnamariense) as poisonous and do not eat it. The evidence is mixed in an unusual way, because this is a species that people demonstrably do eat and that has also killed people, and both facts belong on the page.
An ethnomycological survey in Pu'er, Yunnan lists this species, voucher HKAS-111718, as toxic, collected from natural habitat and not marketed. An Indonesian review documents six Scleroderma poisoning incidents between 2010 and 2020 with 54 victims and 4 deaths, all involving fruiting bodies collected around melinjo trees. If you are in any doubt about an earthball, do not eat it, and seek urgent medical attention for any ingestion.
Yellow Earthball (Scleroderma sinnamariense) poisoning record in Indonesia
The Indonesian record is the most detailed for this species, and it is contradictory in a way that reflects real practice. The review states that this species is sold in some traditional markets, that some communities eat it and others regard it as poisonous, and that consumption is conventionally restricted to the young stage while the interior is still white.
The poisoning cases run from Banjarnegara in 2010 with 4 victims, through Sigli in Aceh in 2011 with 6, Empat Lawang in 2013 with 29, Pekalongan in 2015 with 5, Banjarnegara again in 2017 with 4, and Purwakarta in 2018 with 6. The deaths occurred in the 2013 and 2015 incidents. Symptoms were dizziness, nausea, vomiting, diarrhoea and general digestive disturbance.
Three explanations are offered for the cases, and they are not mutually exclusive. Fruiting bodies were eaten when too old, they were eaten in large quantities, or they were misidentified. One limitation matters for interpretation. The cases are recorded only to genus as Scleroderma species, so they cannot be pinned on this species alone.
Yellow Earthball (Scleroderma sinnamariense) and the wider earthball toxicity record
Onset and duration
Poison centre guidance gives onset between 15 minutes and 2 hours, with symptoms usually subsiding within 3 to 4 hours and full recovery over several days.
Visual disturbance
A German case series records loss of colour vision, double vision and optical hallucinations after S. cepa and S. verrucosum. A Japanese patient reported purple-hued vision.
Cardiovascular collapse
A 66-year-old man lost consciousness ten minutes after eating one fried 2 cm S. albidum, presenting in shock at 53/42 with a heart rate of 52. He was discharged after two to three days.
Neurological effects
A German report describes about 2 grams of dried S. vulgare in soup producing dilated pupils and an effect the author compared with panther cap and fly agaric.
Fatalities beyond Indonesia
The same German series records the death of a three-year-old girl after a strong earthball soup. Anaphylactic shock has been reported from a cooked New Zealand Scleroderma.
Toxin identity
Unresolved. Review literature names sclerocitrin as the agent behind the muscarinic and central nervous effects, while the primary Japanese case report states the toxin is unknown.
There is no human clinical evidence of any kind for this species. No trial, no intervention study, no pharmacokinetic work and no efficacy study exists. The only human data are toxicological, which means any medicinal framing of the Yellow Earthball (Scleroderma sinnamariense) is unsupported by evidence.
The edibility literature also contradicts itself, and readers deserve to see that rather than have it smoothed over. One Thai review cites a Nepalese report of edibility while elsewhere in the same document stating there is no report of it being edible. Hobbyist field sources say flatly that earthballs are not known to be edible. Aggregator sites listing the whole family as edible should be disregarded.
What Makes the Yellow Earthball (Scleroderma sinnamariense) Remarkable?
Yellow Earthball (Scleroderma sinnamariense) as a gymnosperm symbiont
Most ectomycorrhizal fungi partner with pines, oaks, birches, eucalypts and dipterocarps. This one built its best documented relationship with Gnetum, a genus of tropical vines and shrubs belonging to the gnetophytes, an ancient lineage that sits outside both the conifers and the flowering plants. In Cameroon, Gnetum is almost obligately ectomycorrhizal and this fungus dominates the root tips. In Costa Rica it is described as critical to Gnetum leyboldii. A fungus that specialises on a plant group most mycologists never encounter is genuinely unusual.
Yellow Earthball (Scleroderma sinnamariense) yellow pigment above and below ground
The chrome-yellow skin is only the visible part. The root sheath this fungus forms on inoculated melinjo seedlings is also distinctly yellow, against the white sheath produced by the comparison species, and colonies are yellow on every one of the ten culture media tested. The pigment runs through the whole organism rather than sitting on the fruiting body as a surface feature, which is why it works as an identification character even underground.
Yellow Earthball (Scleroderma sinnamariense) dispersal by leaf-cutter ants
At La Selva in Costa Rica, sequences of this species were recovered from Atta leaf-cutter ant nest samples and not from control soils. Researchers also observed ants clipping and carrying away pieces of the skin and the spore mass. Earthballs are usually described as weather-dispersed, splitting open and releasing spores to rain and wind, so an insect route into ant nests is an unexpected addition to that picture.
Yellow Earthball (Scleroderma sinnamariense) nutrient mobilisation traits
The functional toolkit of this fungus is well characterised for a species this obscure. It produces indole-3-acetic acid, the main plant growth hormone, reaching 40.76 micrograms per millilitre at 45 days in tryptophan-supplemented broth, and the crude extract elongated oat coleoptiles in a bioassay. It is siderophore-positive, meaning it secretes iron-scavenging compounds. It dissolves calcium phosphate and hydroxyapatite, producing a solubilisation ring up to 38 millimetres when the mycelium is starved of phosphorus first. It also solubilises zinc carbonate and tolerates lead, growing at concentrations up to 6 millimolar.
Yellow Earthball (Scleroderma sinnamariense) heat tolerance against the temperate norm
Ectomycorrhizal fungi are strongly associated with temperate and boreal forests, and most of the well-studied ones grow best in the low twenties. This species has an optimum of 30 degrees Celsius, grows across 25 to 35, and fails permanently above that with no recovery once cooled. It is a properly tropical symbiont, and its physiology reflects the lowland rainforest it comes from rather than the pine plantations that dominate the mycorrhizal literature.
Yellow Earthball (Scleroderma sinnamariense) research gaps worth knowing about
The open questions on this species are unusually fundamental. Spore ornamentation is reported as both netted and spiny by different authors, and the sectional placement was decided on that character. Spore size differs roughly twofold between Southeast Asian and Amazonian accounts, which points at an unrecognised species complex.
No epitype has been designated and no sequence has been tied to Leprieur 386, the 1840 French Guianan type, so the Asian and Neotropical concepts have never been formally reconciled. There is no genome assembly and only a single BioSample and SRA record for the taxon. The toxin has not been identified. The African host range beyond Gnetum is undefined, and the growth benefit to inoculated hosts is unproven within published trial windows. No conservation assessment exists.
That list is a fair statement of where the science stands. It is also why a well-characterised culture of the Yellow Earthball (Scleroderma sinnamariense) has research value out of proportion to the fungus's obscurity, since the sequencing and physiology work that would close several of these gaps starts with living material.
Also available as a culture plate from Out-Grow.
Yellow Earthball (Scleroderma sinnamariense) Culture PlateFrequently Asked Questions About the Yellow Earthball (Scleroderma sinnamariense)
Can you grow the Yellow Earthball (Scleroderma sinnamariense) to fruiting?
Not on sterile substrate, and not by any published method. This is an ectomycorrhizal fungus, so its fruiting bodies form only where it is joined to the living roots of a host plant. There is no grain spawn protocol, no bulk substrate formulation, no fruiting trigger and no yield figure anywhere in the literature. The mycelium itself is easy enough to culture and grows on ten different tested media. The only route that has ever produced a functioning system is inoculating a compatible Gnetum host, which has been done successfully with root tips, mycelium, spores and both fresh and dried fruiting bodies.
Is the Yellow Earthball (Scleroderma sinnamariense) the same as Scleroderma citrinum?
No, and the name overlap causes real confusion. Scleroderma citrinum is the temperate common earthball of European and North American heaths and oak woods, and it is also widely called yellow earthball. It has a coarsely warted ochre skin, partners with oak and birch, and has its own poisoning literature. Scleroderma sinnamariense is a tropical species with a smoother lemon to chrome yellow skin scattered with dark scales, and its documented host is Gnetum. Most search results for the phrase "yellow earthball" describe the temperate species rather than this one.
Is the Yellow Earthball (Scleroderma sinnamariense) poisonous?
Treat it as poisonous. A Yunnan ethnomycological survey lists it as toxic, and Indonesian records document six earthball poisoning incidents from 2010 to 2020 with 54 victims and 4 deaths, all from fruiting bodies collected around melinjo trees. The complication is that this species is also sold in some Indonesian traditional markets and eaten young, while the interior is still white. Because the poisoning cases were recorded only to genus, they cannot be attributed to this species alone. The safe position is not to eat it, and to seek urgent medical attention for any ingestion.
What does a Yellow Earthball (Scleroderma sinnamariense) look like?
It is a stemless, rounded ball, generally 21 to 64 millimetres across and 10 to 20 millimetres high in the best-described collection, although other accounts give 8 to 10 centimetres. The skin is leathery, 0.8 to 1.5 millimetres thick when fresh, coloured lemon to chrome yellow, and scattered with small dark brown scales. There is a cord of tissue at the base rather than a stem. The interior is solid white when young, then darkens to brown and finally becomes a dry powder of spores. Spore measurements are contested, reported as 4.18 to 6.15 micrometres in one sequenced strain and 7 to 9 micrometres elsewhere.
What conditions does a Yellow Earthball (Scleroderma sinnamariense) culture need?
Warm, slightly acidic and slow. The optimum is 30 degrees Celsius, where the strongest published result reached 56.6 millimetres of colony and 41.33 milligrams of dry biomass. Growth spans 25 to 35 degrees, and above 35 the fungus dies without recovering when cooled. Growth occurs from pH 2.0 to 9.0 with an optimum at pH 5.0. Fungal host agar outperformed all other solid media at 43.5 millimetres in three weeks. In liquid culture, peptone gave the highest biomass at 16.7 milligrams over 30 days, followed by arginine and alanine, while intact protein and glycine barely beat no nitrogen at all.
Where does the Yellow Earthball (Scleroderma sinnamariense) grow?
It was described from French Guiana in 1840, but most records now come from Southeast Asia. Of 227 GBIF occurrences, Malaysia accounts for 83 and Thailand for 35, with further records from Singapore, Vietnam, the Philippines, Laos and Indonesia. The Neotropical set includes French Guiana, Guyana, Brazil and Costa Rica, and there are African records from DR Congo, Cameroon, Burkina Faso and Kenya. Its habitat is tropical lowland forest, where it grows with Gnetum and, in Thailand, on sandy soils in pine forest. Mexican records are now attributed to Scleroderma bermudense instead.