Haasiella venustissima is a saprophytic species confined to natural and near-natural alluvial forests, river sides and creek edges, with a secondary ecological niche in historically old parks. It is a very rare European endemic species, more or less restricted to Central Europe, strongly declining and redlisted in every country (in France as NT). The species is assessed as Endangered because of an estimated reduction of more than 50% over the last 50 years (three generations), a decline projected to continue and caused by
habitat loss and nitrification of potential and existing habitats. This meets the thresholds for listing as EN A2c+3c+4c.

Haasiella venustissima (Fr.) Kotl. & Pouzar ex Chiaffi & Surault 1996
= Haasiella splendidissima Kotl. & Pouzar (heterothallic form, Vizzini et al. 2012)

Very rare european endemic species, restricted more or less to central Europe, redlisted in every country (France as “NT”), strongly declining (in Germany only approx. 3-4 of formerly 28 populations are still exsistent)

Haasiella venustissima is endemic to Europe, with its main distribution in central Europe. It is known from submediterranean to temperate regions, the northernmost recent locations being in Denmark (besides the locus typicus in the Botanical Garden of Uppsala, which has never been verified after Fries 1861). The soecies (incl. H. splendidissima) is reported from 15 countries with the major number of localities in Germany (28 out of 65, Lüderitz & Gminder 2014).

Haasiella venustissima has been described by Fries in 1861 and was refound for the first time in 1949 (Haas xx). Since then appr. 65 locations in 14 countries have been documented (). Many of the locations are one-time-sights and have not been recorded in future years. Only very few stable populations are known, most of them from south-west Germany. Being a bright orange and macroscopically unmistakeable species, it is not very likely to be overlooked by mycologists. On the other hand the occurence in winter periods and its relatively small size give reason for it being underecorded. The real number of locations in Europe is therefore estimated at five times higher, meaning appr. 300-400 localities.

Haasiella venustissima is a wood-inhabiting fungus growing on small branches (more rarely ontruncs ) of decidous trees, mainly Fraxinus or Sambucus. Its main is usually found in natural and near-natural vegetation along big or small rivers in alluvial forests or on creek sides. A few collections were made in traditional old parks with old shrubs.
As the species can survive for a certain time in mesotrophic biotops and even tolerate a moderate eutrophic situation, it can be taken as a signal species for worthwhile re-naturation activities of ruderalized creek systems (Lüderitz & Gminder 2014).

Besides the ongoing loss of habitats, Haasiella venustissima is mainly threatened by the degradation of its biotops. Two main causes can be determined: First are manual changements of the biotops such as channeling or straightening of streams, elimination of the river side vegetation, drainage and lowering of the ground water level and second is the increasing nitrification of the landscape mainly caused by agriculture. A less important thread is the damage of river side vegetation and biotops by free time activities (e. g. fishing).

To prevent further decline it is important to prevent the natural vegetation of river sides and creeks. This means e. g. prohibiton of draining, no or only selective careful forest management, protection areas with prohibition of entering. May be most important is complementary the installation of buffer zones to prevent input of nitrates.

A monitoring of the existent locations is needed to better understand the ecology of this species and especially to document its reactions on possible influences on the biotop.

The species is not known as edible and is neither used as food nor in any other way.

Dahlberg, A. and Mueller, G. 2011. Applying IUCN red-listing criteria for assessing and reporting on the
conservation status of fungal species. Fungal Ecology 4: 1-16.
Lohmeyer, T. R . Haasiella venustissima (Fr.) Kotl. & Pouz., ein “Württemberger Pilz”, erstmals in Bayern nachgewiesen. Ulmer Pilzflora IV: 7-13.
Lüderitz, M. and Gminder, A. 2014. Verantwortungsarten bei Großpilzen in Deutschland. Beiheft zur Zeitschrift fuer Mykologie 13: 1-224.
Pouzar, Z. 1966. Haasiella, a new agaric genus and H. splendidissima sp. nov. Cesk. Myk. 20: 135-140.
Vizzini, A., Consiglio, G., Setti, L. and Ercole, E. 2012. The phylogenetic position of Haasiella (Basidiomycota, Agaricomycetes) and the relationships between H. venustissima and H. splendidissima. Mycologia 104(3): 777-784.