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Which Fungus Is the Largest Organism?

BiologyEcology

Quick Answer

A honey fungus (Armillaria ostoyae) in the Blue Mountains of eastern Oregon, USA, is the largest known organism on Earth — its underground mycelial network spans approximately 9.6 square kilometres and may be 2,400-8,650 years old.

The Full Story

Discovered in 2000 through DNA analysis of Armillaria samples across the Malheur National Forest, this single organism (nicknamed the "Humongous Fungus") extends its network of thread-like mycelia through the soil across about 9.6 square kilometres (3.7 square miles) — roughly equivalent to 1,350 soccer fields. The individual is estimated to weigh at least 6,000 tonnes, though most of its mass is underground and impossible to measure precisely. Its age is estimated at 2,400-8,650 years based on growth rate calculations. Armillaria is a parasitic fungus that kills trees by invading their root systems, causing a root disease called Armillaria root rot. The visible signs are clusters of honey-coloured mushrooms that appear at the base of dying trees in autumn, and black "rhizomorphs" (root-like structures) that spread through the soil at about 1 metre per year, connecting infected trees. Armillaria root rot is a significant problem for forest management worldwide.

Key Facts

1.The Oregon Armillaria individual covers approximately 9.6 square kilometres — making it the largest known organism by area.
2.Its estimated weight is at least 6,000 tonnes, though the true mass is impossible to determine since most of the organism is underground.
3.Armillaria spreads through the soil at about 1 metre per year via black, bootlace-like rhizomorphs that can invade and kill tree roots.

YouTube Angle

Suggested video title for this topic:

"The Largest Living Thing on Earth — A Fungus the Size of a City"