The Role of Mycorrhizae in Plant Health

By Nina Walsh · October 1, 2026

What Are Mycorrhizae

Mycorrhizae are symbiotic associations between fungi and plant roots. Over 90% of land plants form mycorrhizal relationships. These ancient partnerships date back over 400 million years and were essential for plants colonizing land from aquatic environments.

Types of Mycorrhizae

Arbuscular Mycorrhizae (AM)

The most common type, found in vegetables, grasses, and most herbaceous plants. The fungi penetrate root cells and form tree-like structures called arbuscules where nutrient exchange occurs. Glomus species are the most widely studied AM fungi.

Ectomycorrhizae (ECM)

Found primarily on trees like oak, pine, birch, and beech. The fungi form a sheath around root tips and extend into the soil between root cells. ECM networks are responsible for the wood wide web in forests.

Benefits to Plants

Phosphorus uptake increases 10-100 times with mycorrhizae
Drought tolerance improves through extended water access
Disease resistance increases via physical and chemical barriers
Heavy metal tolerance through fungal sequestration
Improved soil structure through glomalin production

Application Methods

Mycorrhizal inoculants are available as powders, granules, and liquids. Apply directly to roots during transplanting. Mix into potting soil at 1-2 tablespoons per gallon. Dip bare-root plants in inoculant slurry before planting.

Protecting Existing Networks

Avoid over-fertilizing with phosphorus, which suppresses mycorrhizal colonization. Minimize soil disturbance from tilling. Reduce fungicide use, as most fungicides harm beneficial mycorrhizal fungi along with pathogens. Maintain living roots in the soil year-round through cover crops.