BIRMENSDORF, Switzerland - Swiss scientists have discovered what they believe is Europe's biggest fungus, stretching wide under an Alpine forest.

The Honey Mushroom ? also known by its Latin species name Armillaria ostoyae ? was found lurking in the Engadine national park in the eastern Swiss Alps, said the Federal Institute for Forest, Snow and Landscape Research. Spanning 35 hectares (86 acres), the fungus it believed to be 1,000 years old, the institute added.

The underground fungus is only visible in the fall, when its mushrooms break through the earth and grow around the roots of trees, the institute said.

Although harmless to humans ? its mushrooms are edible ? the parasitic fungus can colonize trees, killing off swaths of pine forest.

In terms of size, the Swiss fungus is beaten hands down by another Honey Mushroom growing in the United States.

Found in the Malheur National Forest, in eastern Oregon , that fungus covers 890 hectares (2,200 acres) ? making it the largest living organism ever discovered.