Formidable Fungus is World's Largest Organism

Updated August 5, 2020 | Infoplease Staff

Mega mushroom expands in Oregon forest

by David Johnson

This article was posted on December 7, 2000.

(AP Photo/Oregon State University)

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What is probably the largest living organism on earth has been discovered in the Malheur National Forest in eastern Oregon. A fungus living three feet underground is estimated to cover 2,200 acres. After testing samples from various locations, scientists say it is all one organism.

One Thousand Football Fields

Officially known as Armillaria ostoyae, or the honey mushroom, the fungus is 3.5 miles across and takes up 1,665 football fields. The small mushrooms visible above ground are only the tip of the iceberg.

Experts estimate that the giant mushroom is at least 2,400 years old, but could be 7,200 years old.

Previously, the world's largest organism was another Armillaria ostoyae, which covers a mere 1,500 acres near Mt. Adams in Washington state.

A Web of Tentacles

Scientists became interested in that section of forest when trees began to die. The honey mushroom uses tentacles, called rhizomorphs, to take water and nutrients from roots, killing trees.

The process benefits the ecosystem by creating clearings where new plants grow. Animals, such as woodpeckers, live in the dead tree trunks. Mushrooms also recycle nutrients

Dry Climate Helps

The dry climate of eastern Oregon discourages competition from new growth, leaving space for mushrooms already established.

Genetically Closer to People

In other research, scientists have determined that fungi are more closely related to human beings and animals than to other plants.

Moreover, while humans and most species are divided into only two sexes, mushrooms contain over 36,000 sexes.

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