The oaks at Knepp host several extremely rare species of fungi, including the nationally rare robust bracket (Phellinus robustus), and the zoned rosette (Podoscypha multizonata), lacquered bracket (Ganoderma resinaceum) and oak polypore (Piptoporus quercinus) which are rare not just in Britain but in the whole of Europe.
Because these fungi live only on veteran oaks they are important indicators of biological continuity. They tell us that oaks have been in this landscape for hundreds, if not thousands, of years. The spores will have passed down generations of ancient oaks, dating back to the days when Knepp was a Norman deer park and King John used to hunt here.
The reason they are so rare is the scarcity of veteran oaks in our landscape. No one really knows how far the spores can travel but it is unlikely to be a great distance. If the spores from fungi on one old tree do not find the next generation of veteran oaks to colonise, the fungi will simply die with the tree.
The West Weald Fungus Recording Group (WWFRG) runs regular field trips at Knepp, and has compiled a list of over 400 species of fungi since 2015. So far, the focus has been on the larger basidiomycetes so there is scope for more exciting finds in other groups.
As well as fungi associated with old trees, the tightly grazed sward around the castle in the Repton Park supports an array of species associated with unimproved grasslands, including some of our most colourful fungi, the waxcaps.
Ted Green has also recently discovered the newly-described species Suillellus mendax, a mycorrhizal bolete, here.