Mycorrhizal Symbiosis


Hmmm… Mycorrhizal Symbiosis? We are sure you are asking yourself “What is that and how do you pronounce it?” Well, before we answer that question let us ask you a question. What part of the plant is responsible for the uptake of moisture and nutrients? “The roots!” you say?

Although that is a good guess and most likely what you were taught it is actually the mycorrhizae or fungi that live on the roots and in the soil.  The roots are essentially a great anchor system for plants and act as a backup system in case the fungi are lost, but these little fungi do a whole lot more than the roots at bringing nutrients and moisture to your plants.

What are Mycorrhizal Fungi?

3337737Mycorrhizal (pronounced mahy-kuh-rahy-zuhl) meaning fungus-root, are a group of organisms which have been benefiting plants for around 500 million years.  Mycorrhizal fungi live in a symbiotic relationship with plants enabling them to extract nutrients and hold onto water.  The fungus essentially provides a secondary root system that is more efficient and extensive than the plants own root system.

The specialized fungi colonize plant roots and extend into the soil providing the plant with a continued nutrient supply for its entire lifetime.  Basically, the plant performs photosynthesis and other above-ground functions and the fungi, handle the underground nutrition gathering and protect the roots. The Mycorrhizal fungi does expect something in return though. In exchange the plant provides carbon and sugars to the fungi making it a perfect symbiotic relationship.  No wonder 90% of all land plants use this relationship to enhance their own root systems capacity to deliver nutrients!

How do Mycorrhizal Fungi Work?

Mycorrhizal fungi work in a wide variety of ways that benefit the establishment and growth of healthy plants:

  • They increase the surface absorbing area of the roots 10 to 100 times greatly improving the ability and efficiently of the plant to utilize soil borne nutrients.
  • Increase root development.
  • Protect the roots which decrease the risk of disease and insect
  • They release powerful chemicals into the soil that dissolve hard to capture nutrients such as phosphorous, iron and other tightly bound soil nutrients.
  • Increase soil microbial biodiversity.
  • Suppress weedy non-mycorrhizal plants.
  • They form an intricate web that captures and assimilates nutrients, increases water uptake and water storage which causes less stress on plants during droughts.
  • 8312347They reduce plant transplant shock, enhance rooting of cuttings.
  • Give plants increased salt tolerance.

Mycorrhizal fungi improve soil structure by producing humic compounds and organic ‘glues’ that bind soils into aggregates and improve soil porosity, which influence the growth of plants by promoting aeration, water movement into soil, root growth, and distribution.  This is especially important in sandy or compacted soils (hello Cape Town!)

Does my soil have mycorrhizal fungi already?

Whether your soil has mycorrhizal fungi already will depend on a number of factors.  Soils which have not been disturbed are usually full of mycorrhizal fungi (think forests) as well as other beneficial soil organisms. However, there are a number of common practices which can degrade the mycorrhizal fungi forming potential of soil. Ongoing tillage, fertilization, removal of topsoil, erosion, construction of homes and roads, planting of non-native plants as well as a few other practices can reduce or eliminate mycorrhizal fungi.  The reduction of mycorrhizal fungi will affect plant establishment and growth. By reintroducing mycorrhizal fungi into areas where it has been depleted, you will see dramatic improvements in the establishment and growth of plants, trees and shrubs.

In a lot of the areas in Cape Town and surrounds, soils are infertile and sandy and are typically acidic and nutrient deficient – low in organic matter and have poor water and nutrient holding capacities. Adding mycorrhizal fungi to the root of plants in these areas will go a long way to improving plant productivity.

When would you add mycorrhizal fungi?

Mycorrhizal fungi can be added to your gardens at a number of different stages depending on your garden’s needs.  These include:

  • when transplanting trees or shrubs
  • on already established trees and shrubs
  • on garden beds for flowering plants grown from seedlings
  • on plants grown from cuttings or seeds
  • on new or established lawns

Will you still require other fertilizers?

Yes, you will still require other fertilizers, but you can manage your nutrient requirements in a more sustainable manner by reducing your inputs and using these more effectively. Some fertilizers can harm microbial activity in the soil and create fertilizer-dependent plants, so it is important to check whether the plant foods you are using have an effect on the microbial life in your soil.  If you are not sure, you can always check with us and we will be happy to help you out! The best would be if you could get your garden to a point where your plants are more self-sufficient, where they need only crop residues such as mulch and the occasional application of compost and trace minerals.

907847The goal would be to create physical contact between the mycorrhizal fungi inoculants and the plant root. They can be sprinkled onto roots, worked into beds, blended into potting soil or watered in through an existing irrigation system. Generally, you will only need to apply a mycorrhizal to a plant once during its lifetime providing the soil is not depleted due to the practices noted above.

There are a few plants which don’t benefit from mycorrhizal fungi, these are:  Cabbage, Kale, kohlrabi, Radish, Turnip, Rocket, Sedges, Reeds, Wandering Jew, Spiderwort, Rhubarb, Sorrel, Protea, Leucadendrons and Silky Oaks.

The OwnGrown recommendation

Don’t forget this is only one of many ways to give back to your soil. It’s important to look after your soil holistically by being cognizant of what’s happening below the ground. Plants, sun and wind do a great job of stripping our soils of their nutrients, it’s our job as good gardeners to always add to our soil – whether its compost, mulch or beneficial bacteria and fungi, remember to focus on the soil and keep the microbial life happy and everything else will fall into place – take care of your soil and your garden will look after itself!

We are a bit limited with mycorrhizal fungi products in South Africa, but luckily although there are a limited variety of brands out there, there is a product developed specifically for South African soils –MYCOROOT TM.

MYCOROOT TM (New Root Dimensions) has Arbuscular Mycorrhizal (AM) fungi which contain selected combinations of indigenous AM fungi suited to all your needs. Their products have been developed using southern African isolates of Arbuscular Mycorrhizal fungi. These are naturally occurring soil microorganisms, which have not been genetically altered in any way. The product is indigenous, environmentally friendly and produced in an inert clay carrier. If you need some you can order through our online shop here!