There are few known sites where Caulorhiza hygrophoroides has been found, but they are located all across North America. Caulorhiza hygrophoroides has fairly distinctive characters like a brick-red cap and a rooting stem, but rooting stems are often overlooked as they are commonly cut when mushrooms are picked. Also, Caulorhiza hygrophoroides is part of an unpopular group (collybioid) and grows in May, when few mycologists are out in the field. Thus, it is expected that there are many more sites where this species grows but remains to be found and identified. Caulorhiza hygrophoroides was often found in urban forested areas, in polluted/disturbed ecosystems. These sites are negatively impacted by urban sprawl and invasive species. However, Caulorhiza hygrophoroides has been found twice in mature forests in Wisconsin. Thus, its ecology remains to be clarified. It is unclear if this species is restricted to disturbed areas or if the quality of its preferred habitat is declining because of urban sprawl and human disturbance in highly populated areas.
The total number of sites with C. hygrophoroides is estimated to be less than 500 and the total number of mature individuals not to exceed 10 000. No decline of the habitat of C. hygrophoroides is reported.
Therefore, the species is assessed as Least Concern (LC).
= Collybia hygrophoroides Peck 1878.
Caulorhiza hygrophoroides (Peck) Halling, Mycologia Memoirs 8: 100 (1983).
Caulorhiza hygrophoroides is wood-decaying fungus easily identified because of its deep brick-red cap and its longitudinally striate, twisted, solid and tough stem that is strongly rooting (Nelsen 2005). Peck mentionned that after describing this species (1878; as Collybia hygrophoroides), it took 17 years before he found it again. He later suggested that this species is exceptionally rare. Caulorhiza hygrophoroides is said to be rare but locally common by some (Kauffman 1918, Nelsen 2005), but there are very few sites (apparently 14-17) where the species has been found. Six out of 9 observations of this species in the last 25 years are located in Quebec province (Canada) in disturbed and fragmented forest patches within urban areas (Greater Montreal Area). These fragmented forest patches are negatively impacted by urban development. Caulorhiza hygrophoroides was also recently found (latest observation 2015) in Illinois in a suburban protected park where the habitat quality is threatened by uncontrolled spread of invasive species. However, C. hygrophoroides has been found all across the continent, is part of an unpopular group (collybioid) and grows in May. At that time, few mycologists are out in the field. Thus, this species is probably more common than suggested by the limited amount of collections.
Caulorhiza hygrophoroides is reported in Canada from Quebec (Greater Montreal Area; mycoquebec.org, Renée Lebeuf, personal communication and mycoportal.org) and Ontario (GBIF 2013) and in the United States from New York (Albany Co.; Peck 1878), Michigan (Washtenaw Co.; Kauffman 1918, Smith & Weber 1979), Illinois (Cook Co.; Graham 1944 and Patrick Leacock, personal communication), Wisconsin (Vernon Co., Fond du Lac Co.; Nelsen 2005), Arkansas (Ozarks; Swartz 1933) and Oregon (University of Michigan Herbarium #167241).
Caulorhiza hygrophoroides has apparently been found in only 14-17 sites in North America. This species has been mostly reported from disturbed urban/suburban forests, but also from mature forests. Urban/suburban C. hygrophoroides sites are threatened by urban sprawl (Quebec province) and habitat quality loss because of exotic plant species invasion (Illinois), which indicates a risk of decline in C. hygrophoroides population. The only recent mentions of C. hygrophoroides are in Quebec province (6 sites), Wisconsin (2 sites) and Illinois (1 site). Caulorhiza hygrophoroides has never been found during NAMA forays, but these never happen in spring when this species grows.
USA: 1 site in NY (1878), 1-2 in MI (1911//1940; both “Ann Arbor”, could be same location), 1-2 in IL (<1944//1999-2000-2015; no precise locality specified for <1944 report, could be same as a recent report), 2 in WI (1992//1999), 1 in OR (1942), 1 in AR (between 1929 and 1933). Total 7-9 sites. See Nelsen (2005), Schwartz 1933 and mycoportal.org. Also Leacock, personal communication.
Canada: 6 sites in Quebec province (??//??//??//??//2000//2006; all later than 1990) and 1-2 sites in Ontario province (1937//1940; possibly same location). Total 7-8 sites. See mycoquebec.org and GBIF 2013. Also Renée Lebeuf, personal communication.
Given that C. hygrophoroides grows in spring (less forays and fungal surveys) and is part of a relatively unpopular group (collybioid), the species is thought to often be overlooked. Yet, C. hygrophoroides has very distinctive features (deep brick-red cap and its longitudinally striate, twisted, solid and tough stem that is strongly rooting) making it easy to identify when collected properly (i.e., when the rooting stem is not cut).
We estimate the total number of C. hygrophoroides sites to be 50 times higher than the number of sites where it has been found in the last 25 years (i.e., approximately 500 sites). Each site is thought to represent 2 functional individuals. Each of them is expected to represent 10 mature individuals. Thus, we estimate the total number of mature individuals of Caulorhiza hygrophoroides to be under 10 000. The largest subpopulation is located in Quebec province (Canada) and is estimated to include 6 000 mature individuals.
Population Trend: Deteriorating
Caulorhiza hygrophoroides is a wood-decaying fungus growing on buried wood in deciduous forests or along trails (mycoquebec.org). It is a spring fungus growing scattered to gregariously, mostly in May (mycoquebec.org, Nelsen 2005) but also as late as July (Kauffman 1918). Nelsen (2005) mentions that he found the species during five out of the seven years he visited the area near the top of Mount Pisgah (Wisconsin, USA), often in what he believes to be the exact same location. He also mentions that the species can produce fruits on dry years, probably because it grows on buried wood. He never found more than 6 caps at once. He also found Caulorhiza hygrophoroides in Haskell-Noyes Woods (Wisconsin, USA), a forest that is claimed to have never been logged. Therefore, he suggests that Caulorhiza hygrophoroides might be restricted to mature forests. However, other observations are in contradiction with this hypothesis (Y. Lamoureux, personal communication). In Quebec, the species has been found deeply rooted in clay in an opened urban forest, at the bottom of a slope in a muddy pond with shrubs (Rhamnus cathartica, Crataegus sp.), Juglans cinerea and Carya cordiformis and abundant dead elms. In Michigan, Caulorhiza hygrophoroides has been found in a cementery (University of Michigan Herbarium #167023). In Illinois, C. hygrophoroides has only been found in a suburban protected park invaded by exotic species (barberry). Considering that Caulorhiza hygrophoroides has been found in two ecosystemic extremes (i.e., mature stable forests in parks and young disturbed forests in urban areas), its ecology remains to be clarified.
The species has mostly been reported from disturbed urban forests, but also from mature forests. Six out of 9 Caulorhiza hygrophoroides observations in the last 25 years are located in Quebec province in fragmented forest patches within urban areas (Greater Montreal Area). These fragmented forest patches are negatively impacted by urban development. Caulorhiza hygrophoroides was also recently found (latest observation 2015) in Illinois in a suburban protected park where the habitat quality is threatened by uncontrolled spread of invasive species.
Some of the known sites are located in state or municipal parks with a certain level of biodiversity protection. However, most are located in unprotected urban areas, where the risk of habitat loss is high and where possible conservation actions are limited. The ecology of C. hygrophoroides should be further studied before actions are taken, but as a precaution urban parks and forests should be protected. Since Caulorhiza hygrophoroides is easily identified, amateur mycologists could be of great help in describing this species distribution and habitat.
More surveys should be organized in spring (May) to better define the distribution of this species population. As this species has been said to fruit almost every year, it would also be interesting to inventory the currently known sites to evaluate C. hygrophoroides population trends.
The ecology of C. hygrophoroides also needs further study: it has been found both in urban areas and mature forests. It is unclear if its ecological preferences are broad or if its prefered habitat is threatened.
Caulorhiza hygrophoroides is an easily identified species due to its deep brick-red cap and its longitudinally striate, twisted, solid and tough stem that is strongly rooting (Nelsen 2005). In northeastern North America, where C. hygrophoroides is found, there are numerous groups of amateur mycologists. Members of these groups can be recruited and instructed where to find and how to identify C. hygrophoroides so they can target this species during forays. Data from amateur mycologists can be critical to define Caulorhiza hygrophoroides population size, distribution and trends, as well as its ecological preferences.
Caulorhiza hygrophoroides (2015). Retrieved 15 April 2015 from mycoquebec.org
GBIF Secretariat: GBIF Backbone Taxonomy, 2013-07-01. Accessed via gbif.org/species/2531985 on 2016-04-15
Graham,V.O. (1944). Mushrooms of the Great Lakes region. Dover Publications.
Kauffman, C.H. (1918).The Agaricaceae of Michigan Vol. 1. Wynkroy Hallenbach Crawford Co.
Nelson, S. (2005). The false witch’s cap, an unusual fungus from North America. Field Mycology 6 (4): 121-123.
Smith, A. H. & Weber, N. (1979). How to know the Gilled Mushrooms.Wm. C. Brown Co.
Swartz, D. (1933). Studies of Arkansas Fungi. I. Basidiomycetes. The American Midland Naturalist 14 (6): 714-719.
University of Michigan Herbarium #167241 and #167023 - Caulorhiza hygrophoroides. Retrived 15 April 2015 from mycoportal.org