The Humongous Fungus
Deep within Oregon's Malheur National Forest, an enormous life form thrives mostly unseen. This organism, a single genetic individual of the fungus Armillaria ostoyae, covers an area of 2,385 acres, or nearly 3.7 square miles. Its discovery in 1998 redefined the scale of life on Earth. Scientists estimate its age to be at least 2,400 years, and possibly as old as 8,650 years. While other organisms are taller or heavier in a single mass, this fungus is the largest known living thing by total area.
The vast majority of the organism exists underground as a network of thread-like filaments called mycelium. This subterranean body spreads through the soil and tree roots. It also forms black, root-like structures called rhizomorphs, which have earned it the nickname "shoestring fungus." These rhizomorphs are its primary tools for spreading over long distances and infecting new trees. The total weight of the fungus is estimated to be as much as 35,000 tons. The only visible evidence of this massive network appears in the fall, when it produces clusters of honey-colored mushrooms at the base of infected trees. These fruiting bodies, the source of the common name "honey mushroom," are a small, reproductive part of the whole.