The Armillaria ostoyae, popularly known as the honey mushroom, started from a single spore too small to see without a microscope.
It has been spreading its black shoestring filaments, called rhizomorphs, through the forest for an estimated 2,400 years, killing trees as it grows.
It now covers 2,200 acres (880 hectares) of the Malheur National Forest, in eastern Oregon.
It is the largest living organism ever found............(Jeff Barnard - The Independent, UK)

CONSIDERED EDIBLE IF THOROUGHLY COOKED - CAN CAUSE GASTRIC UPSET!