Understanding the role of fungi in soil Tamara Dinter, Dinter Nursery General Manager and Soil Enthusiast
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he term mycorrhiza is often referred to in discussions of ecological gardening practices. But what is it and why is it important? Mycorrhiza refers to the fungus (myco) that grows in and around plant roots (rhiza). Most plant species form associations with root fungi that are mutually beneficial as the fungi receives amino acids and sugars from the plant roots and the plant receives nutrients from the fungi. There are two general types of root fungi. Most are endomycorrhizal associations, with hyphae that penetrate the cell wall (but not the cell membrane), branching out for maximum nutrient exchange. Less common are ectomycorrhizal associations, in which the fungus facilitates nutrient exchange by covering the surfaces of the root tip like a sheath, occasionally passing through a root tip without penetrating the cell walls. Ectomycorrhiza are mainly found with certain
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temperate climate trees (e.g. beech, birch, conifers, oaks, willows). Root fungi are often present in fertile soils and are able to form associations with plants without human assistance. Plants growing in poor soil noticeably benefit from the addition of a commercially available mycorrhizal inoculation. Keep in mind that mycorrhiza added to soil in this way will only thrive if conditions favorable to their growth are met. This means building a good soil texture and nutrient holding capacity (add organic matter!) when adding the fungi. There are many different species of root fungi. Some form associations with certain plants only, while others will form associations with many different plants. To help fungi flourish in your own garden, build soil health by adding organic matter. Once you have established a healthy and thriving soil ecosystem, keep soil disturbance to a minimum. In your vegetable garden, this means avoiding turning the soil when preparing for planting. Loosening soil with a broadfork or pitchfork is sufficient to reduce winter compaction while minimally disrupting the existing fungal networks.
