Agaricus crocodilinus

Agaricus crocodilinus

The Agaricus crocodilinus (Murrill, 1912), often referred to as the giant agaric or giant field mushroom—is a fungus belonging to the Agaricaceae family.

Taxonomy –
Domain: Eukaryota,
Kingdom: Fungi,
Division: Basidiomycota,
Subdivision: Agaricomycotina,
Class: Agaricomycetes,
Subclass: Agaricomycetidae,
Order: Agaricales,
Family: Agaricaceae,
Genus: Agaricus,
Species: A. crocodilinus:
The following term is a synonym:
– Agaricus tabularis Peck ss. Knudsen.

Etymology –
The genus name Agaricus has a very ancient history and derives from the Greek agarikón, a term traditionally associated with mushrooms, while the specific epithet crocodilinus essentially means “crocodile-like.”
The etymology of crocodilinus is thus linked to the appearance of the mushroom’s surface. The image of the crocodile evokes an irregular, finely ornamented, and scaly surface, particularly during certain stages of development. This is a particularly curious reference for a species belonging to a genus where the cap surface, color, and scale structure serve as important diagnostic characteristics.
However, the reference to the “crocodile” should not be interpreted as an indication of a coarsely scaly surface in all specimens. In young individuals, the cap may appear almost smooth; as the mushroom matures—and depending on environmental conditions—the characteristic ornamentation of the cuticle and, above all, the distinctive scaly structure of the stem below the ring may become more pronounced.

Geographic distribution and habitat –
Agaricus crocodilinus is a species primarily associated with temperate zones; it has been recorded in various parts of Europe and North America, as well as in other regions where the species has been introduced or identified. Its typical location is California, in the United States, but its presence is also documented in Europe. For instance, it has been recorded in Italy and the Czech Republic, and is also present in New Zealand, where the first record dates back to 2006.
In Italy, the species has been reported in various settings and appears in regional mycological checklists. A checklist for Tuscany, for example, lists Agaricus crocodilinus as an uncommon species associated with thermophilous oak formations and mesophilous broad-leaved woodlands.
However, its most characteristic habitat remains grasslands and pastures. A fact sheet from the Associazione Micologica Bassa Friulana notes the species’ presence in fields and meadows fertilized with organic matter of animal origin, as well as in parks and clearings within broad-leaved forests.
This preference aligns perfectly with the species’ saprotrophic nature. The mycelium colonizes soil rich in organic matter and thrives particularly well where the decomposition of plant and animal residues ensures a plentiful supply of nutrients.
Fruiting generally occurs during the favorable season—primarily from late summer through autumn in temperate climates. Recent studies in the Czech Republic analyzed specimens collected from a rural meadow near Morašice, in eastern Bohemia, confirming the species’ association with grassy habitats.
It is important to note that an apparently “clean” substrate does not necessarily guarantee low heavy-metal concentrations in the mushroom. A. crocodilinus, in particular, is a notable example of a cadmium bioaccumulator.

Recognition –
The first thing that strikes you when encountering Agaricus crocodilinus is its size. It is a decidedly robust Agaricus, capable of developing very large fruit bodies.
In young specimens, the cap is globose or hemispherical; it later becomes plano-convex and, in mature individuals, can approach a nearly flat shape. According to available descriptions, the diameter can reach about 20 cm, while other sources report even larger dimensions—in the range of 20–40 cm—for particularly well-developed specimens. It is, therefore, a species that can attain spectacular proportions.
The margin lacks distinct striations and, in young specimens, may overhang the gills, sometimes retaining remnants of the partial veil. The cap lacks a true umbo. The cuticle is generally white, whitish, or yellowish; with age, it may take on yellow-ochre hues, especially in the center. Under some conditions, it appears smooth, while in others, it may exhibit slight scaliness.
An interesting characteristic is its tendency to yellow. The surface can develop yellowish tones upon handling—a phenomenon that requires careful assessment, as it can resemble species belonging to the group of yellowing Agaricus species.
The gills are free from the stem, crowded, and thin. In young specimens, they are bright pink or pinkish; later, they turn grayish and, as the spores mature, take on increasingly dark shades, eventually becoming grayish-black or brownish-black. This color change is typical of the genus Agaricus and is linked to the maturation of the spore mass.
The stem is particularly important for identification. It is robust—relatively stocky compared to the size of the cap—and generally cylindrical or slightly swollen at the base. It can reach a length of approximately 6–20 cm and a diameter of 2–4 cm.
Above the ring, the stem is relatively smooth; Below the ring, however, it displays a distinctive ornamentation consisting of scales arranged in concentric bands. This is likely one of the most useful features for distinguishing A. crocodilinus within the complex of large meadow-dwelling Agaricus species.
The ring is superior, membranous, persistent, whitish, and serrated. Its underside may exhibit a characteristic scaly texture. The combination of a large cap, a robust stem, and—above all—the ornamentation on the stem below the ring creates a rather distinctive appearance for the species.
The flesh is white, firm, and compact; when cut, it may take on a slight yellowish tint. The odor is described as pleasant, with notes reminiscent of anise or bitter almond, while the taste is sweet.
Microscopically, as with other Agaricus species, the spores are a key diagnostic feature; however, field identification should not rely on a single element. Within the group of large Agaricus species, there are morphologically very similar species, and definitive identification may require examining numerous characteristics—including microscopic ones and, in complex cases, molecular data.
Particular attention should be paid to Agaricus arvensis, another large, edible, meadow-dwelling species. The ecological and morphological resemblance can be significant.
Even more critical is the potential for confusion with Agaricus xanthodermus, a species that causes gastrointestinal distress and must not be consumed. Surface yellowing alone is insufficient to identify the species.
Identification should therefore be based on a combination of features: habitat, size, cap structure, how the flesh reacts to handling and cutting, odor, ring shape, stem ornamentation, gill characteristics, and—when necessary—microscopic analysis. The Bassa Friulana Mycological Association itself highlights how its large size, growth in meadows, and characteristically patterned stem are particularly useful features for identification.

Cultivation –
Although it belongs to the genus Agaricus, which includes one of the most important species in the global production of cultivated mushrooms, Agaricus crocodilinus is not currently a species of commercial cultivation interest comparable to Agaricus bisporus.
The difference is significant. The common cultivated button mushroom has been selected over generations and benefits from highly standardized production techniques, whereas A. crocodilinus remains primarily a wild species. Its saprotrophic biology, however, makes it possible to grow its mycelium on artificial nutrient substrates.
Recent scientific research has in fact cultured A. crocodilinus mycelium in the laboratory on media based on potato extract, glucose, and agar, generally maintaining it at around 25 °C and in the dark. These cultures have mainly been used to study the physiology of the fungus and the mechanisms involved in metal uptake and regulation, rather than to develop a food-production chain.
Mycelial isolates obtained from fruiting bodies collected in the wild have also been established. In experimental studies, the mycelium was grown on PDA plates and subsequently transferred to liquid culture. This demonstrates that the species can be cultivated under controlled conditions, at least at the mycological and experimental level.
From a practical standpoint, however, it would be incorrect to present these laboratory procedures as a genuine method for domestic food cultivation. For A. crocodilinus, there is currently no established commercial production chain, no standardized food-production protocols, and, above all, no guarantee that the cultivation substrate would not lead to cadmium accumulation in the fruiting body.
The latter point is crucial. The ability to accumulate cadmium is in fact one of the main obstacles to any potential intensive food use of the species.
One of the most fascinating aspects of the biology of Agaricus crocodilinus concerns precisely its relationship with heavy metals.
The species has been described as a cadmium accumulator, and previous studies have reported concentrations that can reach extremely high levels. A recent scientific paper cites values for the species of up to approximately 249 mg of cadmium per kilogram of dry weight, an amount enormously higher than the concentrations normally found in most mushrooms.
This phenomenon is particularly important because it does not appear to depend exclusively on the presence of highly contaminated soils. High cadmium levels have in fact also been observed in specimens originating from environments considered uncontaminated.
One specimen used in a recent study contained 149 mg of cadmium per kilogram of dry weight, a value reported by the authors as approximately one hundred times higher than the typical levels found in mushrooms.
Research is beginning to clarify the molecular mechanisms underlying this characteristic. The fungus possesses cellular transport systems involved in zinc metabolism that may also allow cadmium uptake. One of these transporters, known as AcZIP1, has been studied specifically to understand how the fungus regulates the uptake of zinc and cadmium.
Other studies have identified metallothioneins in the fruiting body, i.e. small proteins rich in cysteine residues that are capable of binding metal ions. In A. crocodilinus, a substantial proportion of the cadmium present in the fruiting body has been associated with a cysteine-rich peptide complex.
This ability has a dual significance. On the one hand, it makes A. crocodilinus an extremely interesting organism for studying fungal physiology and the interaction between fungi and heavy metals; on the other hand, it represents a reason for caution regarding its use as a food source.

Uses and Traditions –
Among the large Agaricus species that inhabit meadows, pastures, and clearings, Agaricus crocodilinus Murrill is one of the most interesting species, both from a mycological and a gastronomic perspective. It is a saprotrophic mushroom, primarily associated with grassy habitats rich in organic matter, which can reach truly remarkable dimensions and which, precisely because of its imposing appearance, is also known in English as the “macro mushroom” or “crocodile agaricus.”
The specific epithet crocodilinus, as mentioned, refers to the surface of the mushroom, particularly to its finely ornamented appearance, which may resemble, at least in the imagination of the person who described it, the skin of a crocodile. The species was scientifically described by William Alphonso Murrill in 1912, based on material from California. The name is now accepted as Agaricus crocodilinus Murrill, although its nomenclatural history is rather complex and includes numerous names that, throughout the twentieth century, were used to designate forms or species now regarded as belonging to this taxon.
The species is particularly interesting for another, less obvious reason: A. crocodilinus has a remarkable ability to accumulate cadmium, a potentially toxic heavy metal, even when it grows in environments that do not necessarily show any obvious contamination. This aspect, which is now the subject of molecular studies, introduces an important note of caution regarding its traditional classification as an edible mushroom.
The species was published by Murrill in 1912 in Mycologia, volume 4, page 300, as part of his studies on the Agaricaceae of the North American Pacific coast. The type material is reported from California. The nomenclatural typification was subsequently clarified through the designation of a lectotype and an epitype, the latter associated with herbarium material.
The historical nomenclature is particularly rich. At different times, the species has been treated under names such as Agaricus macrosporus, Agaricus urinascens, Agaricus albertii, Agaricus nivescens, Agaricus excellens, and various other varietal names or combinations based on Psalliota. The Species Fungorum database brings together a long series of these synonyms under Agaricus crocodilinus, illustrating how complex the taxonomic interpretation of this group has been.
This nomenclatural history is not merely a detail of interest to specialists: it explains why European mycological literature may contain descriptions that apparently refer to different mushrooms but in fact correspond to the same taxon. Among the most important names is Agaricus urinascens, while Agaricus macrosporus was used for a long time in Europe for large Agaricus species occurring in grasslands that are now assigned to A. crocodilinus.
From an ecological standpoint, Agaricus crocodilinus is a saprotrophic mushroom: its mycelium lives in the soil and utilizes organic matter already present in the environment, contributing to decomposition processes and the recycling of nutrients.
Agaricus crocodilinus has traditionally been regarded as an edible mushroom of good gastronomic quality. The substantial flesh, large size, and pleasant odor contribute to its reputation among mushroom gatherers.
Its habitat, predominantly consisting of meadows and pastures, also makes it a typical “country” mushroom, readily recognizable by the contrast between its large, bulky cap and its robust, finely scaly stem.
The information sheet published by the Associazione Micologica Bassa Friulana simply classifies it as edible and emphasizes its distinctive features, including its large size, grassland habitat, and characteristic stem ornamentation.
The term “edible,” however, should not be interpreted as synonymous with “risk-free.” In the case of this species, at least three factors call for caution: the possibility of confusion with poisonous Agaricus species, the frequent presence of insect larvae in the fruiting bodies, and, above all, its ability to accumulate cadmium.
The presence of larvae—or, more precisely, tunnels and infestations caused by the larvae of mycophagous insects—can occur even in relatively young specimens. This is a common phenomenon in many fleshy mushrooms and is not, in itself, an indication of toxicity, but it can rapidly compromise the food quality of the fruiting body.
With regard to cadmium, however, the issue is of an entirely different nature. Cadmium is a food contaminant of toxicological concern, and the ability of this species to accumulate it makes it inadvisable to regard A. crocodilinus as a mushroom for regular consumption in large quantities.
In other words, its traditional gastronomic reputation should be considered alongside modern scientific knowledge of its physiology.

Preparation Methods –
From a culinary perspective, Agaricus crocodilinus can be treated, in terms of the consistency and structure of its flesh, in much the same way as other large edible Agaricus species. Young, healthy specimens are generally the most interesting for culinary use: the flesh is firm and compact, with a greater consistency than that of very mature fruiting bodies.
Before preparation, the fruiting body should be carefully inspected, removing the basal portion of the stem and any deteriorated or heavily infested parts. The mushroom should be thoroughly cleaned of soil and plant debris. Very mature, soft specimens, or those heavily infested with larvae, are poorly suited for consumption.
In the kitchen, it can be sliced and cooked in a pan, where the firm texture of the flesh makes it suitable for a simple yet flavorful preparation. A basic seasoning of extra-virgin olive oil, garlic, and parsley helps enhance its aromatic profile without masking the mushroom’s characteristic odor.
Young specimens can also be used in more elaborate preparations, for example as an ingredient in sauces, side dishes, fillings, or mixed-mushroom dishes. The relatively firm flesh also performs well in preparations where the mushroom needs to retain some structure after cooking.
The fundamental principle, however, is to consume it thoroughly cooked, avoiding treating a large wild Agaricus as though it were an ordinary cultivated button mushroom. Cooking does not, however, eliminate the potential problem of cadmium: heavy metals should not be regarded as contaminants that can simply be “neutralized” by cooking.
For this reason, especially when specimens have been collected from areas where the composition of the soil is unknown, it is prudent to avoid frequent or abundant consumption. The species’ capacity for bioaccumulation is now scientifically documented and constitutes an intrinsic biological characteristic, rather than simply being a consequence of local pollution.
Agaricus crocodilinus is a particularly interesting example of how a mushroom can simultaneously be an organism of considerable naturalistic value, an element of mycogastronomic tradition, and a subject of advanced scientific research.
Its imposing appearance, its cap, which can reach exceptional dimensions, its robust stem decorated with characteristic scaly rings, and its growth in grasslands make it a relatively recognizable species for an experienced mycologist. Its taxonomic history, however, demonstrates how complex the identification of large Agaricus species can be: numerous names used in the past are now considered synonyms of A. crocodilinus.
From an ecological perspective, it is a typical saprotroph of grassy environments and contributes to the decomposition of organic matter. From a scientific perspective, it has instead become an interesting model for studying the interaction between fungi and heavy metals, thanks to its remarkable ability to accumulate cadmium and the molecular mechanisms that enable it to absorb, transport, and sequester this element.
It is precisely this characteristic that calls for greater caution regarding its use as food. The traditional designation of the species as edible should not be considered separately from modern knowledge of its physiology. Even a mushroom regarded as edible can present issues related to the accumulation of undesirable substances.
For a forager, Agaricus crocodilinus therefore remains above all a species to be identified with certainty, observed in its natural habitat, and consumed only with appropriate caution, always bearing in mind that the identification of a wild Agaricus should never be based solely on its large size or the color of its cap.

Guido Bissanti

Main sources:
The morphological description and ecological characteristics used for this article were compared with the data sheet from the Associazione Micologica Bassa Friulana, which also includes observations by Giuliano Ferisin.
Nomenclature was based on Index Fungorum and Species Fungorum, which recognize Agaricus crocodilinus Murrill as the current name and list the species’ complex historical synonymy.
Regarding cadmium, the authors consulted recent studies published in 2025 on metal transport and sequestration mechanisms in A. crocodilinus, as well as earlier Italian literature on heavy metals in the genus Agaricus.

Other Sources:
– Wikipedia, l’enciclopedia libera.
– GBIF, the Global Biodiversity Information Facility.
– Cetto B., 2008. I funghi dal vero, Saturnia, Trento.
– Pignatti S., 1982. Flora d’Italia, Edagricole, Bologna.
– Conti F., Abbate G., Alessandrini A., Blasi C. (a cura di), 2005. An annotated checklist of the Italian vascular flora, Palombi Editore.

Photo source:
– https://www.gbif.org/occurrence/search?view=GALLERY&taxonKey=65NSC&entity=o_6234913418

Please note: Pharmaceutical applications and uses as food are indicated for informational purposes only and do not constitute medical advice; therefore, no liability is accepted for their use for therapeutic, cosmetic, or dietary purposes.