The oaks at Knepp are host to several extremely rare species of fungi - Phellinus robustus; Podoscypha multizonata; Ganoderma resinaceum; and Polyporus quercinus. All of them are rare, not just in Britain, but in the whole of Europe.
Because they live only on veteran oaks, these fungi 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.