0923 GMT February 18, 2020
Scientists first studied the enormous fungus, which lives deep underground in a Michigan forest, in 1992, independent.co.uk reported.
Then they estimated it was 1,500 years old, and the extensive mass of underground fibers and mushrooms that formed it weighed 100,000 kilograms and stretched 15 hectares.
Returning to the site, the same team used more rigorous testing to estimate the fungus was in fact closer to 2,500 years old.
They also discovered that it weighed 400,000 kilograms and stretched over 70 hectares.
This makes the enormous honey mushroom, which mostly consists of an underground network of tendrils wrapped around tree roots, heavier than three blue whales.
“I view these estimates as the lower bound… The fungus could actually be much older,” said Professor James Anderson, a biologist at the University of Toronto who undertook both studies.
Their findings were published in the journal Proceedings of the Royal Society B.
While the Michigan fungus is large, it is outclassed by another honey mushroom from Oregon that is even larger.
There is also the Pando aspen in Utah, a forest originating from a single underground parent clone that is thought to weigh up to six million kilograms.