Most of the fungi you will encounter in a forest are not what you see. The mushrooms above ground are the reproductive structures of organisms that exist primarily as networks of fine threads spreading through soil and through the roots of plants. These networks — collectively called mycorrhizae — form one of the most important ecological partnerships on Earth.
The popular narrative around mycorrhizal networks has expanded rapidly in recent years, sometimes outpacing what the underlying research actually supports. This article explains what these networks are, what they demonstrably do, and where the more dramatic claims need to be qualified.
What a Mycorrhiza Actually Is
A mycorrhiza is a symbiotic association between a fungus and a plant root. The word literally means “fungus root” — and the relationship is intimate enough that, in many species, you cannot easily tell where the plant ends and the fungus begins.
Two main types are most studied. Arbuscular mycorrhizae form inside plant root cells, growing branching structures called arbuscules where exchange happens. They occur in roughly 70% of plant species, including most agricultural crops and grasses. Ectomycorrhizae form sheaths around the outside of roots and grow between the root cells without entering them. They occur in many tree species, including pines, oaks, beeches, and birches.
In both cases, the underlying transaction is similar: the fungus receives sugars produced by the plant through photosynthesis, and the plant receives mineral nutrients — particularly phosphorus and nitrogen — that the fungus is much better at extracting from the soil than the plant’s own roots are.
Why Plants Need This Partnership
Plant roots are limited in their reach. They can grow only where the root tip is, and they extract nutrients from the soil immediately around them. The hyphae of a fungal network are far thinner than the finest plant roots and can extend hundreds or thousands of times the volume of soil that a root system alone could access.
This matters most for nutrients that are scarce, immobile, or chemically locked up in the soil. Phosphorus is the textbook example. In many soils, phosphorus is present but bound to minerals in a form that plant roots cannot use directly. Mycorrhizal fungi produce enzymes that liberate this phosphorus and transport it through their hyphae to the plant.
The relationship is ancient. Fossil evidence suggests mycorrhizal partnerships existed by the time plants first colonized land roughly 460 million years ago. The early colonization of land by plants may have been impossible without fungal partners providing access to soil nutrients.
The “Wood Wide Web” — and Its Caveats
In recent years, popular accounts of mycorrhizae have emphasized the idea that fungi connect different plants together into communicating networks — the so-called “wood wide web.” Trees share carbon. Mother trees feed their offspring. Forests behave as collaborative super-organisms.
The underlying science is more interesting and more complicated than the popular narrative suggests. Common mycorrhizal networks — where the same fungal individual connects multiple plants — do exist, and there is good evidence that nutrients can move through them between plants. Whether this movement is meaningful at ecological scale, whether it is directional in the way some accounts suggest, and whether plants exercise any control over the process remain active areas of investigation.
A 2023 review in Nature Ecology & Evolution examined the evidence for the most widely cited claims about common mycorrhizal networks and found that the support was thinner than the popular accounts implied. The basic phenomenon — that fungal networks can connect plants — is well-established. The interpretation of that phenomenon as deliberate cooperation between trees is much less so.
What the Research Actually Supports
Several findings about mycorrhizal networks are well-supported and important.
Mycorrhizal fungi substantially improve plant access to phosphorus, nitrogen, and water. This effect is large and consistent across studies and across species.
Mycorrhizae influence plant community composition. Plant species that associate with similar fungi tend to grow together; those that associate with very different fungi may experience competitive disadvantages near each other.
The fungal community itself is shaped by the plants present. Different host plants support different fungal communities, and management practices that disrupt fungal communities — heavy tillage, fungicide use, monoculture cropping — can have lasting effects on soil fertility.
What remains less certain is the degree to which mycorrhizal networks function as integrated communication systems. Carbon does move through them between plants under some conditions, but whether plants use them strategically to support kin or signal stress is an open question that current data cannot definitively answer.
Implications for Forestry and Agriculture
The practical implications of mycorrhizal research are substantial. In agriculture, maintaining healthy mycorrhizal communities is increasingly recognized as important for soil health and reduced fertilizer dependence. In forestry, restoration projects that ignore the fungal partners of native trees often fail; replanted forests on disturbed soils may need fungal inoculation to thrive.
For psilocybin mushrooms specifically, the relationship to mycorrhizae is mostly indirect. Most psychoactive Psilocybe species are saprotrophic — they feed on dead organic matter rather than partner with living plants. They participate in the broader fungal community of forests and grasslands without forming the kind of symbiotic partnerships that mycorrhizal species do.
Why the Detail Matters
The story of fungi as the “social network” of forests is genuinely compelling and partly true. But the version that gets repeated in popular media often glosses over what the science actually shows and overstates how well-understood the dynamics are.
Mycorrhizal networks are real. They are biologically and ecologically important. They probably do more than we currently understand. They almost certainly do less than the most enthusiastic accounts claim. The honest position — that this is an active and rapidly evolving area of research where careful claims need to be distinguished from speculative ones — is also the most useful one for understanding what fungi actually do in ecosystems.