British Wildlife Wiki
Hoof Fungus

Hoof Fungus -

Fomes fomentarius commonly known as the Hoof Fungus is a species of plant pathogen polypore found in Europe, Asia, Africa and North America. The very large fruit bodies are shaped like a horse's hoof and vary in colour from a silvery grey to almost black, though they are normally brown. It grows on the side of various species of tree, which it infects through broken bark, causing rot. The species typically continues to live on trees long after they have died, changing from a parasite to a detrivore.


Fomes fomentarius has a fruit body of between 5 and 45 centimetres (2.0 and 18 in) across, between 3 and 25 cm (1.2 and 9.8 in) wide and 2 and 25 cm (0.8 and 9.8 in) thick, which attaches broadly to the tree on which the fungus is growing. While typically shaped like a horse's hoof, it can also be more bracket-like with an umbonate attachment to the substrate. The species typically has broad, concentric ridges, with a blunt and rounded margin. The flesh is hard and fibrous, and a cinnamon brown colour. The upper surface is tough, bumpy, hard and woody, varying in colour, usually a light brown or grey. The margin is whitish during periods of growth. The hard crust is from 1 to 2 mm (0.04 to 0.08 in) thick, and covers the tough yellow-brown trama. The underside has round pores of a cream colour when new, maturing to brown, though they darken when handled. The pores are circular, and there are 2–3 per millimetre. The tubes are 2 to 7 mm (0.08 to 0.28 in) long and a rusty brown colour.

The colouration and size of the fruit body can vary based on where the specimen has grown. Silvery-white, greyish and nearly black specimens have been known. The darkest fruit bodies were sometimes classified as Fomes nigricans. The colour is typically lighter at lower latitudes, altitudes and on fruit-bodies growing on the south side of trees, but studies have concluded no reliable way to differentiate varieties; instead, the phenotypic differences can "be attributed either to different ecotypes or to interactions between the genotype and its environment".

Microscopic features[]

The spores are lemon-yellow in colour, and oblong-ellipsoid in shape. They measure 15–20 by 5–7 μm. The species has a trimitic hyphal structure (meaning that it has generative, skeletal and binding hyphae), with generative hyphae (hyphae that are relatively undifferentiated and can develop reproductive structures) with clamp connections.

Habitat and distribution[]

F. fomentarius has a circumboreal distribution, being found in both northern and southern Africa, throughout Asia and into eastern North America, and throughout Europe. The optimal temperature for the species's growth is between 27 and 30 °C (81 and 86 °F) and the maximum is between 34 and 38 °C (93 and 100 °F). F. fomentarius typically grows alone, but multiple fruit bodies can sometimes be found upon the same host trunk. The species most typically grows upon hardwoods. In northern areas, it is most common on birch, while, in the south, beech is more typical. In the Mediterranean, oak is the typical host. The species has also been known to grow upon maple, cherry, hickory, lime tree, poplar, willow, alder, hornbeam, sycamore, and even, exceptionally, softwoods, such as conifers.


Fomes fomentarius is a stem decay plant pathogen. The mycelium penetrates the wood of trees through damaged bark or broken branches, causing rot in the host. It can grow on the bark wound, or even directly onto the bark of older or dead trees. The decayed wood shows black lines in the lightly coloured decayed areas; these are known as pseudosclerotic layers or demarcation lines. The lines are caused by enzymes called phenoloxidases, converting either fungus or plant matter into melanin.