Ask a Master Gardener

Photo of mycorrhizae fungus on a root



I saw a post on social media about the importance of mycorrhizae in the soil. Why is it important? RG

As we learn more and more about soil, we become increasingly aware that soil is a living entity, not just dirt. Mycorrhizae is a fungus that exists in the soil that has an interesting relationship between itself and plant roots.

The word mycorrhiza means “fungal root” and this fungus exist in a mutually beneficial relationship on and in the roots of many plants. Due to their dependence on plant roots, mycorrhiza are unable to survive very long without a host plant and the plant’s growth is enhanced by the presence of the fungi.

In the classification of mycorrhizae, there are two basic types: ectomycorrhizae and endomychorrhizae. Ectomycorrhizae attach themselves to the ends of young, tender roots and penetrate the outer root cell walls. In contrast, endomycorrhizae penetrate the plant’s roots to live and grow within the plant.

These fungi are considered to be beneficial for up to 90 percent of all plant species. Some of the plants not thought to benefit from these fungi would include azalea, beet, blueberry, broccoli, Brussels sprouts, cabbage/kale, carnation, cauliflower, collards, cranberry, heath, huckleberry, mustard, protea, rhododendron, sedge, and spinach.

This mutually beneficial relationship between fungi and plants exists in the fact that mycorrhizae are not able to produce their own carbohydrates. So, the fungi draw its carbohydrates from the host plant and in exchange the mycorrhizae absorb nutrients from the soil to pass on to the plant.

The parts of the fungus that branch out are called hyphae and these hyphae are much thinner that plant roots. On average, they are 1/60th the diameter of the smaller plant roots. Due to this small size, they can reach into the soil in ways that the larger plant roots cannot. As you can imagine, this increased ability to uptake nutrients is a big plus for the plants. Primarily, the mycorrhiza increases the plant’s ability to uptake water more easily as well as nitrogen, phosphorus, zinc, manganese, and copper.

But that’s not all the benefits. These fungi also help increase drought and salinity stress tolerance, allow for quicker adaptation in transplanted plants, increase crop production, enhanced flowering, and improved soil structure.

While mycorrhizae additives are available for your garden, these fungi can be found in most soils naturally so it’s not necessary to purchase them as an additive. The exception to this would be if you have had a soil test which determined your nutrient levels are correct, but you are still having issues growing plants successfully, it wouldn’t hurt to give you soil a little boost. Mycorrhizal fungi are available as a power, granular, or in a liquid solution. Good luck!

You can get answers to all your gardening questions by calling the Tulsa Master Gardeners Help Line at 918-746-3701, dropping by our Diagnostic Center at 4116 E. 15th Street, or by emailing us at Photo: Robert L. Anderson, USDA Forest Service,