I’ve been hearing a lot about a fungus called mycorrhizae that everyone seems to think I need to add to my garden soil. What is it and do I need to add it to my soil? CG

Mycorrhizae can play a very important role in plant health but because they are unseen, their importance is often overlooked.

Mycorrhiza means “fungal root” and these fungal roots have mutually beneficial relationships with the roots of many plants. Because to this mutually beneficial relationship, mycorrhizae are unable to survive for long outside of the presence of a host plant. There is no downside to this relationship, only benefits.

There are two basic classes of mycorrhizae: ectomycorrhizae and endomychorrhizae. Ectomycorrhizae grow on the ends of young roots and only penetrate the outer cell walls of the root. On the other hand, endomycorrhiza penetrate the plant’s roots and exist entirely within the plant.

Mycorrhizal fungi are considered beneficial for 80 to 90 percent of all plant species. Plants not included in this group include azalea, beet, blueberry, broccoli, Brussels sprouts, cabbage/kale, carnation, cauliflower, collards, cranberry, heath, huckleberry, mustard, protea, rhododendron, sedge, and spinach.

Since the fungus is not able to produce its own carbohydrates, it draws carbohydrates from the host plant. In exchange the mycorrhiza absorbs nutrients from the soil to pass along to the plant.

The branching elements of the fungus are known as hyphae and these hyphae are thinner than the plants roots. They are on average 1/60^th the diameter of the smaller plant roots. Because of their small size they can reach into the soil in ways that the plant’s roots cannot thereby increasing the plant’s ability to uptake nutrients. The main benefit mycorrhizal fungi provide is access to greater amount of water and nutrients such as nitrogen, phosphorus, zinc, manganese, and copper.

Other reported benefits to the presence of healthy mycorrhizae in your garden soil include increased drought and salinity stress tolerance, greater transplanting success, increased crop yield with enhanced flowering, increased water and nutrient uptake, and improved soil structure

Mycorrhizae are available for use as a soil additive for a variety of situations, including vineyards/orchards, nurseries, commercial growers, landscapes, or home gardens. One thing to note is that mycorrhizal fungi can be found in most soils naturally so it’s not always necessary to purchase as a soil additive. However, if you have completed a soil test with results that suggest your nutrient levels are sufficient, but you are still having symptoms of poor nutrient levels, it might be a good idea to add some mycorrhizae to see if the problem corrects itself.

Mycorrhizal fungi are available as granular, powder, or in a liquid solution. Typically, you will find them listed as ingredients in organic fertilizers. 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 mg@tulsamastergardeners.org.

Photo: Robert L. Anderson, USDA Forest Service, Bugwood.org