How Trees Talk to Each Other Underground: The Secret Forest Internet

The Fungal Internet Beneath Our Feet

Let's start with the real stars of this underground story: fungi

When you think of fungi, mushrooms might come to mind. But those are just the fruit—the real action happens underground in thread-like structures called hyphae. These tiny filaments weave through soil, connecting plant roots in what scientists call mycorrhizal networks.

Think of it like this: tree roots are the computers, and fungal threads are the cables connecting them.

These relationships aren't new. In fact, they're ancient. According to the University of Western Australia, "fungi have a deeply ancient evolutionary origin, and colonised land with the first plants around 500 million years ago to form these partnerships" [The Ancient Intimita Relationship Between Trees and Fungi]. Research shows that plants and fungi have been partnering for over 400 million years, long before forests covered the Earth. The University of Western Australia describes this as "an ancient, intimate relationship" that helped plants colonize land in the first place.

What Mycorrhizal Networks Actually Do

Here's what we know for certain:

The Royal Horticultural Society notes that "mycorrhizas are beneficial fungi growing in association with plant roots, and exist by taking sugars from plants 'in exchange' for moisture and nutrients" [Mycorrhizal Fungi]. These partnerships benefit plants in multiple ways, from improved nutrient uptake to better drought tolerance.

But here's where things get interesting—and where we need to be careful about what we claim.

The Mother Tree Hypothesis: Fascinating but Unproven

You may have heard about the "Mother Tree" concept—the idea that older, larger trees act as central hubs, sending extra nutrients to younger saplings and even recognizing their own offspring.

It's a beautiful story. It makes us think of forests as caring communities where elders look after the young.

But here's the truth: there's very little solid evidence for this specific hypothesis.

While mycorrhizal networks definitely exist and do transfer materials between plants, the idea that trees intentionally direct resources to specific relatives or seedlings remains largely theoretical. Some studies show carbon movement through fungal networks, but the purpose and direction of that flow are still debated in the scientific community.

As with many exciting discoveries, the initial findings have sometimes been overstated in popular media. The reality is likely more nuanced—trees may share resources, but whether they do so strategically to help kin specifically is still an open question.

This doesn't make the forest less amazing. It just means we should celebrate what we know while staying curious about what we don't yet understand.

When One Tree Becomes Many: The Clonal Mystery

Now let's shift our focus from fungal connections to something even stranger: trees that aren't really separate trees at all.

Most of us think of a tree as a single organism—one trunk, one root system, one identity. But some species break this rule entirely.

Clonal trees grow from a single ancestor through vegetative reproduction. Instead of seeds, new stems sprout from the same root system. Over centuries or millennia, what looks like a forest of individual trees is actually one genetic individual.

According to ScienceDirect, "Populus tremuloides reproduces asexually by sending up root suckers that develop into new stems, creating extensive clonal colonies in which all ramets share an identical genotype" [Poplar Genome Sequence: Functional Genomics in an Ecological Dominant Plant Species].

Why This Matters

This changes how we think about:

• Age: A clonal colony can live thousands of years, far beyond any single stem's lifespan
• Size: Some colonies cover hundreds of acres
• Identity: Are these forests or single organisms?

Pando: The Trembling Giant

And now we arrive at the crown jewel of clonal trees: Pando.

Located in Utah's Fishlake National Forest, Pando is a grove of quaking aspen (Populus tremuloides) that spans approximately 106 acres and weighs an estimated 6,000 metric tons. Every visible tree trunk shares the same root system and genetic makeup.

According to Live Science, "Pando is a giant aspen clone in central Utah that has been regrowing parts of itself for up to 80,000 years" [Pando the Worlds Largest Tree and Heaviest Living Organism].

Pando at a Glance

That's older than agriculture. Older than written language. Older than most human civilizations.

Each spring, new stems emerge from the shared root system. Each fall, they turn brilliant gold before dropping their leaves. Through fire, drought, and human development, Pando has persisted—though it now faces threats from grazing animals and changing land use.

Fungi vs. Aspen: Who Holds the Title?

Here's where things get truly mind-bending.

If Pando is one of the largest organisms, there's another contender that might beat it: Armillaria ostoyae, a honey fungus in Oregon's Malheur National Forest.

This single fungal organism covers approximately 2,385 acres (over 1,600 football fields) and is estimated to be 2,400 years old.

According to the USDA, "the Malheur National Forest in eastern Oregon's Blue Mountains is... 'one of my favorite gross places in America.' A Malheur National Forest cluster of Armillaria ostoyae, or honey mushroom, is part of the world's largest fungus, which engulfs 3.4 square miles -- that's 2,200 acres -- of Oregon" [Fungus Among Us].

Both are remarkable. Both challenge our understanding of what counts as "one organism." And both remind us that nature operates on scales that dwarf human experience.

The Bigger Picture: Life on Earth

When we zoom out even further, humans become surprisingly small players in Earth's biological story.

According to Our World in Data, humans make up just 0.01% of Earth's total biomass. The vast majority belongs to plants, bacteria, and yes—fungi.

National Geographic's food web resources remind us that every organism plays a role in interconnected systems. Trees, fungi, animals, microbes—all linked in networks we're only beginning to map.

A Whimsical Reflection

There's something humbling about standing beneath Pando's golden canopy, knowing you're looking at thousands of stems that share one heartbeat.

We like to think of ourselves as individuals, separate and distinct. But maybe the forest teaches us otherwise. Maybe connection is more natural than isolation. Maybe the boundary between "self" and "other" is softer than we imagine.

Whether through fungal threads or shared roots, life finds ways to link together. To share. To persist.

Listen to the Forest

So, what can you do with this information? You don’t need to be a scientist to appreciate the Wood Wide Web.

1. Change Your Walk: Next time you visit a park or a forest, try to imagine the invisible threads beneath your feet. Visualize the sugar and water flowing between the trees. It changes the way you see the silence.
2. Protect the Mycelium: If you garden, avoid using harsh chemical fungicides or deep tilling that destroys the fungal networks in your soil. Let the fungi do their work.
3. Plant Native: Native trees and plants have co-evolved with local fungi. Planting native species helps restore these ancient communication lines in your local ecosystem.
4. Respect the Old Ones: If you see a massive, ancient tree, treat it with reverence. Perhaps it's a Mother Tree, a hub of knowledge and life for the whole grove.

Join The Hidden Thread

Did you enjoy this peek into the hidden world? There is so much more to discover about the patterns of nature. From the migration of monarch butterflies to the rhythm of the tides, the world is full of secrets waiting to be found. 👉 [Subscribe to The Hidden Thread newsletter] to get a new story of wonder delivered to your inbox every week. No spam, just curiosity.

Book tip:

"The Hidden Life of Trees" by Peter Wohlleben – Available on Amazon, this accessible book explores how trees communicate and support each other. While it touches on similar themes, it presents a balanced view of what we know versus what remains speculative. You can find it on Amazon here.

Sources Used and Further reading

According to the University of Western Australia, "fungi have a deeply ancient evolutionary origin, and colonised land with the first plants around 500 million years ago to form these partnerships" [https://www.uwa.edu.au/news/article/2022/february/the-ancient-intimate-relationship-between-trees-and-fungi]

According to the Royal Horticultural Society, "mycorrhizas are beneficial fungi growing in association with plant roots, and exist by taking sugars from plants 'in exchange' for moisture and nutrients" [https://www.rhs.org.uk/biodiversity/mycorrhizal-fungi]

According to ScienceDirect, "Populus tremuloides reproduces asexually by sending up root suckers that develop into new stems, creating extensive clonal colonies in which all ramets share an identical genotype" [https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/populus-tremuloides]

According to Live Science, "Pando is a giant aspen clone in central Utah that has been regrowing parts of itself for up to 80,000 years" [https://www.livescience.com/planet-earth/plants/pando-the-worlds-largest-tree-and-heaviest-living-organism]

According to the USDA, "the Malheur National Forest in eastern Oregon's Blue Mountains is... 'one of my favorite gross places in America.' A Malheur National Forest cluster of Armillaria ostoyae, or honey mushroom, is part of the world's largest fungus, which engulfs 3.4 square miles -- that's 2,200 acres -- of Oregon" [https://www.usda.gov/about-usda/news/blog/fungus-among-us-author-names-oregons-humongous-fungus-one-grossest-places-earth]

According to Peter Wohlleben (William Collins), "The Hidden Life of Trees" explores how trees communicate and support each other [https://www.amazon.com/Hidden-Life-Trees-International-Communicate/dp/0008218439]

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