Entoloma madidum is a fungus of semi-natural, unimproved grassland. It is a member of the Entoloma bloxamii s.l. complex where it is readily identifiable by both macro- and micromorphological characters. The number of records of this species has steadily increased over the past 10 years since it was formerly described, though remains one of the rarer species in the group. Older records attributed to Entoloma bloxamii s.l. cannot be readily separated and not used in this assessment. Entoloma madidum is found throughout western Europe from the Pyrenees and Sardinia in the south, central Norway to the north and Ireland and southern Finland in the east. The EOO is estimated at >4,000,000 km2 across 5 subpopulations. The AOO is estimated to be in the range of 1,500-2,000 km2 with the number of locations more or less equal to the number of sites (i.e. c. 200). There is uncertainty over the population size, but expected to be within the region of 2,500-10,000 mature individuals. As with E. bloxamii s.l. and other grassland fungi, there has been a genuine reduction in population size of E.madidum, inferred through the loss of extent and quality of grassland habitat, largely due to agricultural improvement and more recently, abandonment. The loss of suitable grassland habitat is estimated to be 30-50% over 3 generations (a generation assumed to be c.17 years). The declines have not ceased and likely continue over the next 50 years. The species is therefore assessed as VU (A2c+3c+4c). 

Taxon: Entoloma madidum Noordel. & Hauskn.
Taxonomic group: Fungi – Basidiomycota – Entolomataceae
Taxonomic notes:
Entoloma madidum was described by Noordeloos & Hausknecht during the modern revision of the Entoloma bloxamii sensu lato group. It represents a distinct molecular lineage formerly included within the broad blue‑grey “bloxamii” concept of Gillet (1874), but is now recognised as a separate species based on combined molecular and morphological evidence.
Molecular data (ITS and additional loci) show E. madidum to form a stable, well‑supported lineage within the blue‑grey Entoloma complex. Historically, many collections now attributable to this species were recorded as E. bloxamii s.l., but sequence‑anchored studies confirm its separation. Diagnostic features include typically darker, more saturated blue‑grey to violaceous basidiomes, often with a moist or wet appearance (reflected in the epithet madidum), and consistent micromorphological characters of the spores and pileipellis that distinguish it from E. bloxamii s.str. and related taxa.

There are records of E. madidum from North America, however North American material is now believed to be a separate species E. medianox (Schwartz, 2015).

Ecologically, E. madidum shows a tendency toward moist to periodically damp, nutrient‑poor grasslands, differing from the core habitats of E. bloxamii s.str. Only a subset of historical material can be confidently reassigned to this species, and modern, sequence‑anchored recording is therefore central to understanding its distribution and rarity.
Recognition of E. madidum as a separate species is important because it represents a distinct evolutionary lineage within the former bloxamii aggregate, has consistent morphological and ecological traits, and differs in distribution and scarcity from other segregate taxa. Treating it separately improves the accuracy of Red List assessments and site‑based conservation evaluations.

Entoloma madidum warrants global Red List assessment because it was formerly included within the globally Vulnerable Entoloma bloxamii sensu lato aggregate, but modern taxonomic clarification shows that it is far rarer, more fragmented, and more ecologically specialised than previously understood. The species is known from a small number of sites across Europe, each supporting very few individuals, and it occupies moist to periodically damp, long‑established, nutrient‑poor grasslands that continue to decline due to agricultural intensification, hydrological alteration, nutrient enrichment, abandonment, and scrub encroachment. These pressures indicate a continuing decline in both habitat quality and population size. Given its small inferred global population, severe fragmentation, and ongoing habitat loss, E. madidum may qualify for a higher threat category than the former aggregate, and therefore merits consideration for assessment at the Endangered level.

Entoloma madidum is widespread but scarce across parts of Europe. Verified, modern records show a scattered pattern, with relatively few confirmed sites in each country or region, reflecting the fragmented nature of long‑established, nutrient‑poor grasslands on which it depends. As with other species formerly included in E. bloxamii s.l., many older records cannot be reliably assigned, so the true distribution is likely under‑recorded.

Where sequence is confirmed, E. madidum occurs in semi-natural lowland and upland grasslands, but it is never abundant and typically appears at low frequency even at known sites. Sequenced, modern‑concept records confirm its presence in: Great Britain, Ireland, Denmark, Netherlands, Germany, Austria, Sweden, and Norway.  Additional confirmed records, consistent with the clarified species boundaries, are known from: Switzerland, Czech Republic, Slovakia, Poland, and France.

Based on GBIF records, the estimated EOO for is 4,200,000 km2 (GBIF, 2026). Based on the distribution of E. bloxamii s.l., this is probably a reasonably accurate estimate of EOO. Significant populations are found in Great Britain and Norway and Denmark. There are an estimated 197 localities (tetrads) from c.360 occurrences with an estimated AOO of 788 km2. This is likely to be an underestimate due to the recent taxonomic change and more sites for the species are expected to be identified. However, E. madidum does appear to be genuinely more restricted than others in the E. bloxamii s.l. group.  On this basis, a reasonable upper estimate of AOO would be double the current known AOO at about 1600 km2. 

The recent separation of Entoloma madidum from E. bloxamii s.l. means that direct quantitative population data is only available for the last 10 years at most. Entoloma bloxamii s.l. is red-listed as Vulnerable (Jordal 2019). While this improved taxonomic clarity has increased the number and reliability of recent records, it does not represent any genuine increase in population size.

E. madidum is strongly associated with semi‑natural, unimproved grasslands. These habitats have undergone major historical and ongoing declines in both area and ecological quality. Griffith et al (2013) estimated that there had been a 90% loss of habitat for grassland fungi from the CHEGD group of fungi (grassland fungi of Clavariaceae, Hygrocybe s.l., Entoloma, Geoglossaceae, Dermoloma and allies) over the preceding 75 years. The Food and Agriculture Organization of the United Nations (FAO 2006) similarly identified declines in semi-natural grasslands of 12.8% over 13 years (FAO, 2006) - equivalent to a rate of loss of almost 1%/year. Furthermore, the remaining sites are typically small, isolated, and increasingly fragmented. At the global level, the population decline is estimated at 30-50% in 50 years (past, present and future, corresponding to approximately three generations: one generation is assumed to be about 17 years), meeting the threshold for VU (A2c+3c+4c).

There is a continuing decline in AOO that is inferred from the well‑documented loss, degradation, and fragmentation of suitable habitat across its range. There are 5 subpopulations (assuming subpopulations to be separated by 500km (Dahlberg and Mueller, 2011)): British Isles and Ireland ; southern Scandanavia; Central Europe; the Pyrenees; and Sardinia. An estimated 95% of the population is within the British Isles and Scandanavia subpopulations. As such, the population is not considered to be severely fragmented. The number of locations is probably equal to the number of sites.

The estimated population size for E. bloxamii s.l. was estimated at <20,000 (Jordal, 2019). E. madidum appears to be rare within the E. bloxamii complex, so a cautious upper estimate of population size is between 2,500-10,000 mature individuals. 

Entoloma madidum occurs in semi‑natural grasslands, typically in moist to wet swards with long continuity of low‑intensity management. It favours moist, base‑rich to circumneutral grasslands, but can also occur in damp, slightly acidic sites where local hydrology or disturbance creates suitable microhabitats. It is most often recorded in pastures, meadows, and old churchyards where soil moisture remains relatively high throughout the year. Fruiting is usually in late summer to autumn.

The main threats to Entoloma madidum are those affecting semi‑natural grasslands across Europe. While there are some threats like habitat loss to agricultural conversion that are a threat across its range, they are not uniform and dependant on local factors. The number of locations is therefore likely to be close to the number of sites. The threats to E. madidum include:
•Permanent land-use change to development. 
•Agricultural intensification, such as fertiliser application, reseeding, and ploughing, which leads to the conversion or “improvement” of long‑established grassland.
•  Changes in grazing regimes, particularly intensification under small‑holder systems, which alter sward structure and reduce suitability for fruiting.
•  Abandonment of traditional management, resulting in scrub encroachment and other ecosystem modifications that close the grassland canopy.
•  Tree planting and afforestation, often preceded by herbicide application to clear vegetation, permanently altering habitat, soil conditions (including competition from ecto-mycorrhizal species) and microclimate.
•  Herbicide use in non‑agricultural settings, including clearance for wildflower “meadow creation”, amenity grassland management, and routine spraying around graves in cemeteries, all of which disrupt soil fungal communities.
•  Eutrophication from airborne nitrogen deposition, favouring competitive grasses and reducing fungal diversity.
•  Fragmentation and loss of landscape continuity, isolating remaining high‑quality sites.
These processes have caused long‑term declines in both the extent and quality of suitable habitat.

Conservation actions
No species‑specific conservation measures are currently targeted at E. madidum, but it benefits from:
•  Protection and favourable management of semi‑natural grasslands, including low‑intensity grazing or mowing.
•  Avoidance of fertiliser inputs and reseeding.
•  Prevention of tree planting on high‑value grassland sites.
•  Maintenance of long‑term habitat continuity at known and potential sites.
Continued use of modern species concepts and, where possible, molecular confirmation is important for monitoring and site evaluation.

To strengthen future assessments and conservation planning for E. madidum:
1.  Expand sequence‑anchored recording to refine distribution maps and confirm species boundaries.
2.  Re‑examine historical collections, where material exists, to clarify long‑term trends and past range.
3.  Do population genomics to understand impact of fragmentation on gene flow
4.  Dispersal and autecology
5.  Study long-term impact of reduced grazing/ increased sward height on population size.

Entoloma madidum has no known use or trade.