The monstrous mushroom lives in the subsoil of a Michigan forest (United States) and belongs to the species Armillaria gallica, an edible honey mushroom. It was discovered in the late 1980s, but thanks to new analyzes its fascinating features have been updated. It is estimated to be 2,500-years-old and covers 370,000 square meters, details that make it one of the oldest and largest organisms on our planet.

In the subsoil of a Michigan forest, in the United States, there is a colossal mushroom much larger and older than previously suspected. When it was discovered in the late 1980s, scientists estimated an age of 1,500 years, a weight of 100,000 kilograms and an extension of 120,000 square meters, about 30 acres (12 hectares). Truly "monstrous" features, which made this mushroom belonging to the Armillaria gallic species – a normal honey mushroom – one of the largest and oldest living organisms on Earth.

An international research team led by scholars from the universities of Toronto and Missouri has returned to analyze the giant buried in the Crystal Falls forest, and from the new analyzes conducted both on site and in the laboratory has determined that the mushroom is even more incredible. According to scholars led by Professor James B. Anderson, the mushroom weighs four hundred thousand kilograms and covers 370 thousand square meters, almost 40 hectares. Scientists have also determined that the specimen of Armillaria gallica is 2,500 years old. From the sequencing of its genome it has been shown that it has not "evolved"; in its DNA only 163 of the 100 million base pairs that make up the genetic makeup have changed. According to Anderson and colleagues this is due to the fact that the mushroom lives mainly below ground and it is minimally affected by surface changes. The exposed parts, the yellow-brown "honey mushroom", are nothing more than its sexual organs: it is precisely from the genetic analyses conducted on them that scientists discovered that they were clones, all coming from the same gigantic organism.

If a living being of this type frightens and outclasses in terms of size a blue whale (Balaenoptera musculus), the largest animal on the planet, anyway it is not the most colossal mushroom on the planet. The record belongs to another mushroom, the basidiomycete Armillaria ostoyae found in a forest of the Blue Mountains of Oregon in 1998. This mushroom covers about nine million square meters (900 hectares) and could be older than 8 thousand years. This means that it could have arisen and grown before civilization itself. However, the most probable age is 2,400 years. The new details on the Michigan mushroom have been published on the website for scientific research bioarxiv.org, pending publication in an ad hoc journal after data review.