Trees and Soil Fungi

When caring for trees, it’s easy to see fungi as the enemy since it often causes disease and decay. However, there are mycorrhizal fungi that help trees. Symbiotic associations between trees and soil fungi are absolutely critical for optimum tree health and growth.

heart shape soil

Benefits of Soil Fungi

Mycorrhiza is a symbiotic relationship, a biological interaction that is mutually beneficial, between a fungus and a plant. In this case, the fungi exist in the tree’s root system. The mutual relationship provides a home and carbohydrates for the fungi.  For the tree, presence of the fungi make it easier for it to get moisture and more nutrients from the soil.  The result is better growth and root development.

Creating a Healthy Soil Environment

There is no question scientifically that mycorrhizal fungi benefit trees. Even so, debate still exists about how to best encourage these associations. Most research shows that plants perform better with mycorrhizas. However, only a few experiments show any benefit to trees when adding mycorrhizal fungi are to soil.

Many times this is because spores in store-bought mycorrhiza packs are dead on arrival. Product selection is also important because trees have very specific fungal associates, which vary based on species, environmental conditions, soil type and more.

Perhaps the most important reason several studies show little benefit from adding mycorrhizal fungi to trees is that no attention was paid to improving the soil conditions in these studies. Soils that lack mycorrhizas are usually already in poor shape. For example, they may be too hot, too dry or wet, or lack organic matter or oxygen. Without first addressing the soil problems, any added fungi will soon perish.

A better option is to start by creating a soil environment in which natural and applied mycorrhizas can flourish. Properly mulching trees, de-compacting soils, managing moisture, and adding organic matter are all methods for improving soil biology. By creating a soil environment as similar as possible to the forest floor, trees and their beneficial microbes will thrive.

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