It is known to be one of the largest living organisms, where scientists have estimated a single specimen found in Malheur National Forest in Oregon to have been growing for some 2,400 years, covering 3.4 square miles (8.4 km²) and colloquially named the “Humongous Fungus.”
Armillaria solidipes grows and spreads primarily underground and the bulk of the organism lies in the ground, out of sight. Therefore, the organism is not visible to anyone viewing from the surface.
It is only in the autumn when this organism will bloom “honey mushrooms”, visible evidence of the organism lying beneath.
If the last posting depicted possibly the most horrific appearing fungus, this one takes the cake for both largest and oldest, even though most of its biomass is hidden beneath the forest floor.