In the quiet forests of the Blue Mountains in Eastern Oregon, lies an organism of gigantic proportions. In fact, it’s the largest living organism (by area) on Earth. But if you visit, don’t expect to be enthralled by its impressive size, because you can’t actually see it. This giant organism is Armillaria solidipes and it is one HUMUNGOUS fungus.

Spanning an area of nine square kilometres – that’s nearly 1300 rugby fields – this fungus lies hidden beneath the soil surface. The only signs that it’s there are copses of dead trees and little “honey mushrooms” that sprout in autumn. For an estimated 2,400 years it has been stretching its black filaments (rhizomorphs) through the ground and invading tree roots. Infected roots are covered by mats of white mycelium – structures which suck water and carbohydrates from the trees, feeding the parasitic fungus.

Because of this pathogenicity towards trees, scientists wanted to figure out how they might control Armillaria fungus. In 1998, scientists took samples from infected trees in the area and compared cultures grown from these samples. To the scientists’ surprise, this revealed that most of the samples came from a single organism – one enormous fungus attacking hundreds, or even thousands, of trees.

It is thought that the dry climate in Eastern Oregon has facilitated the growth of this ancient fungus giant. A dry climate makes it difficult for new spores to establish, leaving plenty of room (and trees) for the older organisms to spread.

This fantastically enormous specimen of Armillaria solidipes is an astounding feat of nature – and it reminds us that nature includes more than just plants and animals. Let’s not forget about the weird and wonderful fungi kingdom and all it has to offer: from delicious truffles to life-saving antibiotics, and of course the world’s largest organism.