Cryptomyces maximus (commonly known as willow blister) is a species of fungus within the genus Cryptomyces.

Cryptomyces maximus is the only species listed on The world's 100 most threatened species as being native to the British Isles.

It prefers to live in damp and humid environments such as swamps.

They can be found in a variety of different climates also so it is not just bound to one.

They prefer both alpine and mountainous areas, along with the lowlands of Germany and the UK.