The Size of This Mushroom Is Impressive. But What Is the Largest Fungus in the World?

Fungi are not only one of the most mysterious living organisms but also the largest on Earth. The size of this mushroom will fascinate you.

A mushroom enthusiast in the Czech Republic, Europe, Martina Ostrýžová, recently shared her excitement after discovering a massive boletus mushroom during a foraging trip. "It weighed 2.9 pounds (1.3 kg), had a diameter of almost 17 inches (42.5 cm), and a cap circumference of over 40 inches (102.5 cm)! I found it just 50 feet (15 m) from the road in the forest," she said, proudly posting pictures of her impressive find.

For mushroom hunters, finding a boletus of this size is a huge accomplishment, but even larger mushrooms have been discovered. In 2022, for example, a 9 pound (4 kg) boletus was found by Luis Merino in Puerto del Pico, Spain.

But if you're wondering what the largest fungus in the world is, it's not just about the above ground part. Fungi's underground networks, called mycelia, are often much larger than the mushrooms we see. In fact, one species not only holds the title for the largest fungus but also the largest living organism on Earth!

Meet Armillaria ostoyae, a fungus that's common in the forests of the western U.S. While the above ground portion is a modest brownish mushroom growing on tree bark, its underground network stretches for miles through the forest floor in the form of black, thread-like structures known as "shoestrings." These networks are so vast that scientists estimate a single Armillaria ostoyae in northern Michigan covers 90 acres (37 hectares) and weighs up to 880,000 pounds (400,000 kg)!

Even more impressive, a specimen in Oregon's Malheur National Forest is the largest living organism on the planet by mass, area, and volume. It spans nearly 4 square miles (10 km²) and could weigh a staggering 77 million pounds (35,000 metric tons).

Adding to the wonder, Armillaria ostoyae is bioluminescent, meaning it glows in the dark, a phenomenon called "foxfire." This eerie glow has even sparked the idea of creating glowing trees to light up city streets in the future!

If you're feeling adventurous, why not grab a basket and explore your local woods? Just be sure to learn how to identify safe mushrooms before you go! Who knows, you might just discover your own hidden treasure.