The roots of a tree grow deep into the soil to anchor it in place, but they do far more than hold the tree steady.
Roots are vital to a tree’s survival. They absorb water from the soil, which then travels up through the trunk to the leaves. There, the water is used during photosynthesis, the process by which the tree makes its food.
But there's much more happening beneath the surface. Hidden in the soil is something else that’s crucial to the tree’s health: fungi. We usually recognise fungi as mushrooms that pop up in forests, especially in autumn. But those mushrooms are just the fruiting bodies - the part used for reproduction. The real magic happens underground!​
Below the surface, fungi grow as long, thin, white threads called mycelium. These thread-like structures look like strands of a spider’s web, spreading out through the soil. Mycelium feeds on dead leaves and wood, helping to break them down. Without fungi, organic matter wouldn't decompose properly, making fungi essential to the ecosystem.
But mycelium doesn’t just clean up the forest floor. It also forms an extraordinary partnership with trees.
Scientists have discovered that some mycelium strands grow right up to the tree’s tiniest roots, known as root hairs. The tree provides the fungi with sugars produced during photosynthesis.
In return, the fungi deliver vital nutrients like nitrogen and phosphorus back to the tree.
This helpful exchange is known as symbiosis.
But the relationship goes even further.
Recent research shows that this mycelial network acts like a natural underground internet. Trees can use the mycelium to share resources. A dying tree, for example, might transfer its remaining nutrients to support nearby trees. Stronger trees can help weaker or younger ones by sending them extra nutrients, especially in dark, shaded areas of the forest.
Even more astonishingly, trees can use this network to communicate. If pests like aphids attack one tree, the mycelium can send warning signals to neighbouring trees, boosting their defences before the pests reach them.
In other words, trees have a secret social network beneath our feet. They communicate, share, support, and protect one another using the mycelium of fungi.
It’s a real-life Wood Wide Web!