Hydnum repandum (Wood Hedgehog)
At this time of year you can commonly encounter creamy-coloured fungal fruit bodies in our woods. Closer inspection will show that instead of gills beneath the caps, these fruit bodies have long teeth or spines which hang down perpendicular to the ground. It is these features that give these fungi their common name of the Hedgehog mushrooms. The spines actually have the same function as the gills, producing the reproductive spores for dispersal.
There are, in fact, a number of different fungal genera which produce fruit bodies bearing teeth-like structures and many were thought to be closely related and therefore grouped together as the stipitate or stemmed hydnoid fungi. However, DNA studies showed that this tooth feature was evolved on a number of occasions. Surprisingly, the genus Hydnum is more closely related to the orange Chanterelle than any of the other toothed fungi.
The most commonly encountered Hedgehog fungus in the UK is Hydnum repandum (Wood Hedgehog) (see photos). It is usually pale yellow, cream to ochre coloured with soft flesh which stains orange when bruised. The cap can be 5-15 cm in diameter, and often irregular in shape, having an incurved margin and is sometimes slightly cracked. The stem 3-7 x 1-3 cm is typically acentric and the spines, 2-7 mm long. The latter cover the whole under surface of the cap and also may grow someway down the stem.
The spore print of hedgehog fungi is white, although under the microscope the spores appear translucent and smooth. Like other Basidiomycete fungi, Hydnum species produce the spores on microscopic elongated spore producing structures called basidia. But in Hydnum these have a lengthwise division and are referred to referred to as stichobasidia. This lengthwise division is a shared feature with chanterelles which supports the DNA placement of Hydnum in this group.
Hydnum repandum is a popular edible wild mushroom, which is fairly easy recognizable due to its distinctive appearance. The flesh can be bitter in older specimens, therefore thorough cooking is recommended, although it has been suggested that the bitterness can be removed by brushing off the spines. When served together with Chantarelles, they have a delicious, slightly oyster-flavoured taste.
Occurrence:
The fungus is commonly found from July to November.
Habitat:
Commonly found in beech, birch and coniferous forests often growing on the ground in clusters or together with chanterelle.
Distribution:
Hydnum repandum is widely distributed throughout Europe, North America, Japan, Tasmania and Australia.
Other species:
Other Hydnum species which occur in Scotland are H. rufescens and the newly described and probably much overlooked H. ellipsosporum. Both species are distinctly smaller than H. repandum reaching up to 8 and 5 cm in cap diameter, respectively. The colour of both species is also darker with a distinctive orange hue. The cap-stem ratio is much smaller in both compared to H. repandum. Furthermore, there is an abrupt transition between the cap and stem in these two species compared to a rather smooth transition in H. repandum. Hydnum rufescens and H. ellipsosporum are very similar to each other on macroscopic scale and are distinguishable microscopically as H. ellipsosporum has larger, clearly ellipsoid spores compared to the smaller, round to oval spores of H. rufescens. Ecological data on the distribution of the three species is confused due to the misidentification of H. ellipsosporum with H. rufescens. It remains to be seen if they prefer different habitats. So go out and find some and add to our knowledge of the very interesting hedgehog fungi.
Please remember to submit your records to your local recording group or via the Scottish Fungi online recording form.
By Peggy Ehrlich and Andy Taylor, November 2014
Hydnum repandum photos by Peggy Ehrlich
Hydnum ellipsosporum by Liz Holden
Hydnum rufescens by Robert Goodison
Hydnum repandum distribution map
The National Biodiversity Network Gateway records from FRDBI andHBRG datasets are shown on the above map but note that more recent records may be available via the Gateway (see terms and conditions at http://data.nbn.org.uk). Data providers and the NBN Trust bear no responsibility for any further analysis or interpretation of the information in the map.
Note also that additional records may be available on the Association of British Fungus Groups CATE2 database, but these are not available via the NBN Gateway.