Fungi are neither plants nor animals but belong to their own kingdom. They are unable to produce their own food through the process of photosynthesis, as plants do; instead, they acquire nutrients from living or dead plants, animals, or other fungi, as animals do. In many larger fungi (lichens excepted) the only visible parts are the fruit bodies, which arise from a largely unseen network of threads called 'hyphae'. These hyphae permeate the fungus's food source, which may be soil, leaf litter, rotten wood, dung, and so on, depending on the species. With the exception of the earpick fungus Auriscalpium vulgare, all stipitate hydnoid fungi are ectomycorrhizal species; they form close symbiotic relationships with trees, and derive some of their nutrients from the tree's roots. This aids them in obtaining nutrients on poor quality soil, and means that are always found in association with trees (1).
Hydnellum spongiosipes is associated with oak, sweet chestnut, and less frequently beech, alder, birch and hawthorn; this provides an easy, but not necessarily accurate way of distinguishing between this species and H. ferrugineum, which occurs mainly under pine (1).
The best time of year to look for the fruit bodies of Hydnellum species is September. Interestingly, all Hydnellum species show very low levels of invertebrate damage; it is possible that they may contain protective chemicals that may also protect them from grazing mammals (1).