Mycorrhizae are fungi naturally found in the soil that form beneficial relationships with the roots of plants. In exchange for sugars provided by the plant, the slender branches of mycorrhizae can offer an extended reach for nutrients and other resources and impart greater plant resilience in periods of stress.

They are of enormous importance to plants in nature, but studies have shown that the addition of commercial mycorrhizal inoculants to garden and planter soil are generally ineffective. Cultivated plants are also less reliant on these structures as their growing environment and medium is more carefully tended and improved. 

Soil that is high in organic matter will naturally invite fungi into the soil. Gardeners will do more for their plants by building healthy soil than by adding mycorrhizal products which may not be a match for their plants or remain in the soil. Organic compost refreshments to gardened areas, limiting soil disturbance and compaction, avoiding the use of fungicides and high phosphate products will all assist with the natural colonization of the soil by beneficial mycorrhizae. 

Courtesy of NYBG Plant Information Service