Several Phellodon species were placed on a preliminary Red List of threatened British fungi because of a general decline of the genus in Europe.

Species grow in a symbiotic mycorrhizal association with trees from the families Fagaceae (beeches and oaks) and Pinaceae (pines).

Accurate DNA-based methods have been developed to determine the presence of Phellodon species in the soil, even in the extended absence of visible fruitbodies.

Although Phellodon fruitbodies are considered inedible due to their fibrous flesh, the type species, P. niger, is used in mushroom dyeing.

Donk's original family concept included the genera Bankera and Phellodon, whose species produce hyaline (translucent) and echinulate spores (covered with small spines).

[6] This taxonomic rearrangement was rejected by Rudolph Arnold Maas Geesteranus in 1974, who showed that the tuberculate spores of P. niger were the result of an immature specimen.

[8] Modern molecular phylogenetic analysis places Phellodon in the thelephoroid clade (roughly equivalent to the order Thelephorales) along with the related genera Bankera, Hydnellum, and Sarcodon.

Although the status of the Bankeraceae has not been fully clarified with molecular genetic techniques,[9] Phellodon is classified in this family by authorities on fungal taxonomy.

[14] The fruit bodies of Phellodon species have caps and stipe, and thus fall into the general category of stipitate hydnoid fungi.

[18] In conditions of high humidity, P. niger can form striking drops of black liquid on the actively growing caps.

[18] Cystidia are either absent, or present infrequently as incompletely differentiated cystidioles (sterile cells about the size of an immature basidium).

[15] In a preliminary assessment for a red list of threatened British Fungi, P. confluens, P. tomentosus, and P. melaleucus are considered vulnerable, and P. niger is rare.

In the case of Phellodon tomentosus, for example, there is little correlation between fruitbody appearance and below-ground mycelium, making it hard to determine the distribution and rarity of the fungus with standard surveying techniques.

[27] Phellodon melaleucus and P. niger were included in a Scottish study to develop species-specific PCR primers that can be used to detect the mycelia of stipitate hydnoids in soil.

Phellodonic acid, which exhibits antibiotic activity towards bacteria and other fungi, was the first bioactive compound reported from any member of the order Thelephorales.

[33] P. niger has been a source for several bioactive compounds: the cyathane-type diterpenoids, nigernin A and B; a nitrogenous terphenyl derivative, phellodonin; 2',3'-diacetoxy-3,4,5',6',4''-pentahydroxy-p-terphenyl; grifolin; and 4-O-methylgrifolic acid.