Using Mycorrhizal Fungi to Boost Plant Health and Yield

Healthy soil is alive with microscopic partners that help plants thrive. Among the most important of these are mycorrhizal fungi—beneficial soil organisms that form a partnership with plant roots. This living network helps plants take up nutrients and water more efficiently, improving both growth and yield. In regenerative gardening, fostering mycorrhizal fungi is key to building long-term soil health.

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What Are Mycorrhizal Fungi?

“Mycorrhiza” means “fungus-root.” These fungi live in close association with plant roots. The fungus threads, called hyphae, grow through the soil, extending far beyond the root zone. In exchange for sugars from the plant, the fungus gathers water and nutrients—especially phosphorus, zinc, and copper—and delivers them back to the plant.

There are two main types:

Ectomycorrhizae, which form a sheath around roots (common in trees and shrubs).
Endomycorrhizae (also called arbuscular mycorrhizae), which grow inside root cells (common in vegetables and most garden plants).

Benefits in the Regenerative Garden

Improved nutrient uptake: The fungi act as a living extension of plant roots, reaching nutrients roots can’t access.
Better water efficiency: Mycorrhizal networks help plants tolerate drought by drawing moisture from deep in the soil.
Healthier soil structure: Fungal threads bind soil particles, improving aeration and preventing erosion.
Natural disease protection: Mycorrhizae crowd out harmful microbes and trigger plant immune responses.
Higher yields: Plants with strong root-fungal partnerships grow faster and produce more abundant harvests.

How to Encourage Mycorrhizal Fungi

Avoid synthetic fertilizers and pesticides. These chemicals can kill or weaken beneficial fungi.
Disturb the soil as little as possible. Tilling breaks up fungal networks that take months to rebuild.
Feed the soil, not the plant. Add compost, leaf mold, or mulch to provide steady organic matter.
Keep living roots in the soil. Cover crops and perennials help sustain fungal populations year-round.
Plant diverse crops. Fungal species thrive when they can partner with a wide range of host plants.

Using Mycorrhizal Inoculants

You can introduce beneficial fungi directly by using mycorrhizal inoculants—powders, granules, or liquids containing spores.

How to apply:

Dust seeds or dip transplant roots in the inoculant before planting.
Mix granules into planting holes for trees or shrubs.
Water liquid inoculants into established beds early in the season.

One application is often enough; once established, the fungi multiply naturally in healthy soil.

Signs of a Thriving Mycorrhizal Network

Plants have strong, evenly developed roots.
Soil stays moist longer after watering.
Crops grow more evenly with fewer nutrient deficiencies.
Earthworms and other soil life are abundant.

In My Garden

In my Sonoma Valley garden, I’ve seen the power of mycorrhizal fungi firsthand. When I plant tomatoes, peppers, and onions with a dusting of inoculant, they root faster and need less water through the dry summer. In raised beds that I don’t till and keep covered with mulch year-round, fungal growth is visible as fine white threads weaving through the soil. Those are living signs of fertility—nature’s own underground network keeping the soil and plants in balance.

Regenerative gardening is about working with life, not against it. Mycorrhizal fungi are among your best allies—quiet workers that strengthen every plant and make the soil truly alive.