What is Mycorrhizae?
Most of us think of mycorrhizae as a fungus, but really, it is the beneficial symbiotic relationship between a fungus and a plant. This relationship benefits both the plant and the fungus.
With the plants above ground, it is easier to see the benefits the plants receive from this, but the fungus also takes advantage of this partnership. The mycorrhizae aid the plant with growth, improved strength, increased root absorption area, while the fungus receives carbon from the plant.
Below I hope to be able to explain how these benefits and functions of mycorrhizae help our bonsai.
Benefits for Plants
One function of this beneficial relationship provided by the fungi in the soil is in its ability to exchange nutrients with their surroundings and their host plant. The increased surface area that the fungi provide for the roots, allows the fungus to absorb more nutrients for its host. This network of fibrous fungi growth is able to absorb water, inorganic phosphorus, mineral or organic nitrogen, and amino acids through transport cells located on their membrane. Once the water and nutrients are absorbed, they can then be transferred to the plant, who in return supplies carbon.
Benefits for the Fungi
Because Mycorrhizae is the symbiotic relationship between a plant and fungi, its not just the plant that benefits. The fungus benefits from the relationship as well. While helping plants with the uptake of nutrients and water, the plants will give somewhere between 10% and 20% of the carbon they obtain from photosynthesis to the fungus. Everyone is happy.
How does this Relate to Bonsai?
The Bonsai Pot and Roots
Our goal for the roots of a bonsai is to have a mat of fine feeder roots that are able to absorb water and nutrients throughout the whole pot. But some species have thicker roots than others and this makes it more difficult to form the fine mat that we are looking for. If we are unable to fill the pot with fine feeder roots, it’s more difficult to absorb enough water and nutrients and the plants will suffer. This is where mycorrhizae play a role with our bonsai. One way to look at this relationship between the plant and the fungi is that the fungi almost acts as fine feeder roots. By colonizing the areas between the roots, it increases the absorption area. With this relationship, we increase the health of the plant and roots. This increased health will increase the number of fine feeder roots.
Bare Rooting Conifers
One reason we do not bare root conifer bonsai is because of this symbiotic relationship. If you remove all of the soil, you are also removing the fungi and the relationship it had with the tree. Conifers, in particular, rely heavily on fungi to transform nutrients into a form that they can use. By removing the fungus, you are removing a vital part of the root zone. In some cases, it is enough to kill a tree. I like the half bare root method to repotting conifers. Repotting black pine in nursery soil
Healthy Roots, Healthy Bonsai
I have always said that if you can’t grow roots, then you can’t grow bonsai. Of course, it is more than that, but it’s true. If the root zone is healthy then you will have a healthy bonsai. If the root zone is unhealthy and dies then the bonsai dies.
Especially in conifers, you want to see the fuzz in your soil. This is the fungi growing and this indicates a healthy root zone. This is going to do a couple of things. 1) It will increase the absorption area of the roots. This allows the roots to absorb more water and nutrients to transport to the bonsai. 2) With the increase in nutrients to the bonsai, the plant will respond with healthier growth. This growth will be in the form of more back buds, shorter internodes, and increased ramification. This increased ramification will also increase the ramification of the roots, meaning finer roots. This circles us back to the “The Bonsai Pot and Roots” section. Sometimes you will notice mushrooms growing in your pots. This is a great indicator that your soil is loaded with fungi and is “active” if you will.
Fertilizing to Promote Mycorrhizae
You will hear some people say that some plants don’t need mycorrhizae to survive. This is true to some degree. If you are providing enough nitrogen and phosphorus in forms that are easily used by the bonsai, fungi will not grow and you will not have that beneficial relationship. This usually happens in bonsai when we use inorganic fertilizers. These fertilizers are fast acting, can burn the root hairs, and harm the fungus.
What happens is that you make that plant “dependent” on a steady stream of readily available nutrients.
Organic fertilizers provide enough nutrients for the plant to grow, however, they are slower acting. Also, fungi are needed to break down those nutrients into a form that the bonsai can absorb. The organic fertilizer promotes or “feeds” the fungus and the fungus feeds the bonsai. The organic fertilizer should break down slowly over time (usually 4-6 weeks). This network of fuzz in our soil slowly breaks down the nutrients in the organic fertilizer so the bonsai has a steady food source that promotes healthy roots.
To wrap up this article, I want to reiterate that mycorrhizae are important for plant health. Especially in conifers. This symbiotic relationship is one of the most important things we can cultivate for a healthy root zone along with a healthy bonsai. If you are using inorganic fertilizer and then paying money for a mycorrhizae product, you are wasting your money. Switch over to an organic fertilizer that promotes the root zone, as Sumo Cakes does. In the end, your bonsai will be happier.