Right now, beneath your feet, something extraordinary is happening. Thread-like fungal filaments—some thinner than a human hair—are creating an underground internet that connects nearly every plant in your yard. Through this network, your established trees are literally feeding your struggling seedlings. Plants are warning each other about pest attacks. Nutrients are flowing through highways you cannot see.

And if you’re gardening the way most Americans garden, you’re probably destroying it.

This isn’t speculation. Over the past two decades, researchers like Dr. Suzanne Simard at the University of British Columbia have documented what Indigenous peoples have known for millennia: forests—and by extension, gardens—are not collections of individual plants competing for resources. They’re communities, connected and communicating through fungal networks that scientists call the “Wood Wide Web.”

while the science has been widely publicized, almost no one is explaining what this means for the person with a ¼ - 3 acre lot, a container garden on a balcony, or a community plot in an urban neighborhood.

My goal for today is to change that.

To understand why this matters, you need a basic picture of how mycorrhizal fungi work. (Mycorrhiza comes from Greek: mykes meaning fungus, rhiza meaning root.)

Here’s the arrangement: Fungal threads called hyphae wrap around or penetrate plant roots. The plant provides sugars—up to 30% of everything it produces through photosynthesis—to the fungus. In exchange, the fungus extends the plant’s effective root system by orders of magnitude, accessing water and nutrients (especially phosphorus) the roots could never reach alone.

But it gets more interesting. Those same fungal threads connect to other plants. And through those connections, resources flow.

Dr. Simard’s research in Pacific Northwest forests documented carbon moving from paper birch trees to Douglas firs growing in shade—the birch essentially subsidizing the fir’s survival. When she killed the birch trees, the connected firs suffered. The network wasn’t just beneficial; it was load-bearing.

Similar patterns appear in agricultural research. Tomato plants connected through mycorrhizal networks show increased resistance to blight when neighboring plants are infected—the healthy plants receive chemical signals through the fungal network and upregulate their defenses before the pathogen arrives.

This isn’t magic. It’s biology. And it’s happening—or trying to happen—in your garden right now.

Here’s where the science becomes immediately practical.

Mycorrhizal fungi evolved to help plants access phosphorus in soils where phosphorus is limited. When phosphorus is abundant, plants don’t need the fungi—and the relationship breaks down. The fungi can’t colonize roots that don’t need them.

The threshold: approximately 50 parts per million of available phosphorus in soil.

Above this level, mycorrhizal colonization drops dramatically. The fungi are still present in the soil, but they can’t form the partnerships that create the network.

Why does this matter? Because most synthetic fertilizers—and many organic ones—contain significant phosphorus. The familiar N-P-K numbers on fertilizer bags (10-10-10, for example) tell you the ratio of nitrogen, phosphorus, and potassium. That middle number is phosphorus.

If you’ve been fertilizing regularly for years, your soil phosphorus levels may be well above 50 ppm. Many suburban yards test at 100-200 ppm or higher. At those levels, the mycorrhizal network can’t establish no matter what else you do.

Beyond excessive phosphorus, three common gardening practices devastate mycorrhizal networks:

Fungal hyphae are incredibly fine—much thinner than plant roots. When you till soil, you’re not just “loosening” it. You’re shredding the hyphal network into fragments. It’s like taking scissors to a spider web.

The network can regrow, but it takes time. Annual tilling means the network never fully establishes. This is one reason no-till farming and no-dig gardening produce increasingly good results over time—they allow fungal networks to develop and persist.

This should be obvious but often isn’t: fungicides kill fungi. Mycorrhizal fungi are fungi.

Even targeted fungicides applied to plant foliage can impact soil fungi. And “organic” fungicides like copper sulfate are particularly persistent in soil, accumulating over seasons of use.

The irony is sharp: we often apply fungicides because plants are struggling with disease. But those disease struggles may partly result from weakened mycorrhizal networks that would otherwise boost plant immunity. We’re treating symptoms while worsening the underlying cause.

Mycorrhizal fungi need living plant roots to survive. Without host plants, the network dies.

This matters for fallow periods. If you leave garden beds bare over winter, or clear an area completely for renovation, the mycorrhizal network in that zone loses its host plants and degrades. When you replant, you’re starting the network-building process over.

It also matters for plant selection. About 80% of plant species form mycorrhizal partnerships, but the brassica family (cabbage, broccoli, kale, mustard) and the amaranth family (spinach, beets, chard) do not. A bed planted exclusively with these crops won’t maintain a mycorrhizal network for neighboring plants.

If you’ve been gardening conventionally for years, your mycorrhizal network is probably compromised. Here’s how to rebuild it—with honest acknowledgment of what we do and don’t know.

Before adding anything, stop subtracting. Cease tilling. Reduce or eliminate synthetic fertilizers (especially phosphorus). Minimize fungicide use. Keep living roots in the ground year-round through cover crops, perennials, or overwinter crops.

This alone—simply stopping the destruction—will allow natural recovery. Mycorrhizal spores are present in most soils, and networks can reestablish once conditions allow.

Mycorrhizal inoculants—products containing fungal spores—are increasingly available to home gardeners. They come as powders, granules, or liquids that you apply to seeds, transplant roots, or soil.

The science on inoculation is genuinely mixed, and I want to be honest about that.

Where inoculation helps most: Severely degraded soils. New construction sites where topsoil was removed. Container gardens using sterile potting mix. Land previously used for intensive conventional agriculture. In these situations, native mycorrhizal communities may be absent or severely depleted, and inoculation can jump-start the network.

Where inoculation may be unnecessary: Gardens with established perennials and minimal disturbance already likely have functional mycorrhizal networks. Adding inoculant may not improve on what’s already there. Some research shows native, locally-adapted fungi outcompete commercial strains.

What we don’t know: Whether commercial strains persist long-term. Whether they integrate with or displace native fungi. Whether the species in commercial products are optimal for your specific conditions and plants. The research is ongoing.

Mycorrhizal fungi are fueled by carbon from plants. But they also benefit from carbon in soil—particularly fungal-friendly forms like woody mulch and ramial wood chips (chips from branches under 3 inches diameter).

The contrast with fertilizer is important: Fertilizer feeds plants directly, bypassing the mycorrhizal partnership. Carbon feeds soil biology, including the fungi themselves. One approach weakens the network; the other strengthens it.

Arborist wood chips, applied as mulch 3-4 inches deep, are one of the best things you can do for mycorrhizal networks. They provide carbon, maintain soil moisture, moderate temperature, and create fungal-friendly conditions at the soil surface. Fungal hyphae visibly colonize the mulch layer over time—you can see it as white threads when you pull back the chips.

Everything above assumes you have ground to work with. But 36% of American households rent, and many more garden primarily in containers. Does any of this apply?

Yes—with modifications.

Container gardens: Sterile potting mixes contain no mycorrhizal fungi. If you want the network, you must inoculate. Commercial inoculants work well here—this is actually their ideal use case. Apply when potting and maintain living roots year-round (don’t dump and refill containers annually; instead, top-dress and maintain perennials or overwintered crops). Avoid excessive fertilization, especially synthetic slow-release types with phosphorus.

Community gardens: You can’t control neighboring plots, but you can build networks within your own. The benefits are real even at small scale. Consider adding perennial elements (a fruit bush, permanent herb patch) that maintain year-round mycorrhizal hosts while you rotate annuals around them.

Rental yards: You may not be able to stop a landlord from chemical lawn treatments, but you can build network refugia in beds you control. Even a small untreated area maintains mycorrhizal communities that can recolonize larger areas later. Document what you’re doing—you might negotiate with future landlords based on demonstrated results.

I want to end with some perspective.

Mycorrhizal networks don’t stop at property lines. Your yard connects to your neighbor’s yard connects to the park down the street connects to the remnant woodlot at the edge of the suburb. In undeveloped landscapes, these networks extend for miles.

Urbanization and conventional land management fragment these networks. Every tilled lawn, every over-fertilized bed, every hardscaped yard is a break in the system. Over time, the connected whole becomes disconnected islands.

When you stop destroying your mycorrhizal network, you’re not just helping your tomatoes. You’re maintaining a node in a larger system. Your garden becomes a refuge—a piece of functional ecosystem that other fragments can eventually reconnect to.

This isn’t a solution to climate change or biodiversity collapse. Those require systemic change beyond individual action. But it’s not nothing. It’s one way we can, on the land we actually control, create conditions for recovery rather than continued degradation.

The fungi are still there, in most soils. They’re waiting for conditions that allow them to rebuild. You can create those conditions. The network wants to exist.

Let it.

Finding the Mother Tree by Suzanne Simard — The accessible book-length treatment of Dr. Simard’s research on forest networks.

Mycelium Running by Paul Stamets — Broader look at fungi in ecosystems, including practical applications.

Society for the Protection of Underground Networks (SPUN) at spun.earth — Research organization mapping global fungal networks; excellent resources section.

— Mike Ruggiero
Ruggiero Sustainable Solutions
Lehigh Valley, Pennsylvania