Which Is the Largest Living Organism?

The "Humongous Fungus" is a single individual of Armillaria ostoyae (honey fungus) growing in the Blue Mountains of eastern Oregon. Genetic sampling has confirmed that its underground network of root-like mycelium spans approximately 9.6 km² (about 3.7 square miles) and is estimated to be 2,400 to 8,650 years old. Most of the organism lives underground, feeding on tree roots, and is visible on the surface only when it produces mushroom fruiting bodies. By mass, the organism may weigh over 6,000 tonnes. Other contenders include a vast quaking aspen colony named Pando in Utah, which covers 0.43 km² but consists of genetically identical clones.