Bitter Bolete - Tylopilus felleus

Bitter Bolete – Tylopilus felleus

Fungi of the Week

1st February 2021 | Info

Common name: Bitter Bolete

Scientific name: Tylopilus felleus

Introduction: The Bitter Bolete (Tylopilus felleus) is a UK-native fungus which often forms as a singular fruiting-body. The name felleus comes from “fel,” which means “bile” and refers to the bitter taste of this fungus.


Cap:  Young caps of a Bitter Bolete are convex with a slight velvety feel. Typically, they are a warm orange colour with the occasional one having a green-brown undertone. As the fruiting-body proceeds to mature, the cap will flatten to be applanate and darken to a deep brown, losing its velvet-like touch. These changes may cause the cap to split and/or cause wavy margins to develop. The width of caps typically varies from around 6-12cm but have been known to be larger.

Pores/Tubes: When young, the tubes of a Bitter Bolete are a cream colour but, as they mature, they become pinker. They are very small and are densely packed, ending in tiny pores that become coral-like in colour as the fruiting-body matures. They are delicate and will turn brown once touched or bruised.

Stem: Slightly bulbous-like in appearance, the stems of a Bitter Bolete thicken towards their base and are often curved and chunky. The entirety of each stem is covered in a brown reticulate pattern and can be up to 8cm tall.

Spores: Sub-fusiform with a clay-pink spore print.

Flesh: Bitter Boletes tend to have a white-coloured flesh which does not change colour if cut open.

Habitat/Impact on Trees

Bitter Boletes have an ectomycorrhizal (symbiotic without penetrating the plant’s cell walls) relationship with Oak, Beech, and other broadleaf trees. However, they do also have a mycorrhizal (fully symbiotic) relationship with some conifers. Typically, you will find that the Bitter Bolete forms singularly; however, they can also form in small groups. Quite often, this will happen between late summer to late autumn.

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