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Mycorrhizae: Down and Dirty with Symbiotic Fungi

Whether you’re brand new to the world of plant care, have had your hands in the soil for years, or you’re somewhere in between, one of the most important things you can do to understand and support the health of your plants is to learn about their relationships with the organisms around them. Especially when it comes to houseplants or food gardens, it can be intimidating and even a little scary to realize that the soil your plants are growing in is chock-full of life. Bacteria, fungi, and all manner of microorganisms make their homes in and around the roots of every type of plant, houseplant or otherwise. But never fear! Biodiversity in your soil is inevitable and is actually one of the most important factors in keeping your plant happy and healthy.

One of the most important types of relationships for your plants is that between their roots and the fungi that inhabit the soil around them. The kingdom of Fungi is one of the largest, most diverse, and most mysterious collections of organisms in the world. It includes everything from the mushrooms on your pizza to the yeast that makes your bread rise to the lichen that grows on tree trunks. Some of the most important fungi, however, are much smaller and harder to see. They live their lives below the surface of the soil and quietly toil away among the roots, ensuring the success of the plants around them.

These are called mycorrhizal fungi, which breaks down into “myco” meaning fungus, and “rhizae” meaning root. There are countless species of mycorrhizal fungi, but the most important thing to know about them is that they form a symbiotic relationship with the plants with whom they cohabitate. This means that the plants and the fungus both benefit from living with each other. 

There are two main groups of mycorrhizal fungi: endomycorrhizal and ectomycorrhizal. Both of these types of fungi have bodies made of very fine filaments in the soil around the roots of plants. The difference between these two groups is that ectomycorrhizae exist very closely around the roots of plants, while endomycorrhizae actually penetrate the roots with their cells. Neither of these relationships are harmful to the plants in any way, and in fact both are beneficial and necessary. For a brief explanation of why this is true, we have to travel way, way back in history-- to a time when the world looked a little different. 

White mycorrhizae filaments on tree roots.

Millions and millions of years ago, the world was warm and wet. Plants, much like animals, lived only in the ocean. The aquatic lifestyle was preferable to these primitive organisms because it was a lot easier to obtain all of the necessary nutrients from the water around them rather than braving the dry land. Here’s where the fungi enter the picture. Once these very early plants began forming their close relationships with soil fungi, it became a whole lot easier for them to take in everything that they needed through their roots. This is one of the major factors that allowed plants to spread and take over the land that was previously inhospitable to them.

Here’s how it works: the long filaments of fungi that associate with the roots of plants take up nutrition from the soil. The fungi don’t actually use many of these nutrients, but when they absorb them, they become available for the plant to use. The filamentous body of the fungi essentially become extensions of the roots of the plant, hugely boosting their ability to absorb everything they need from the soil around them. In exchange, the fungi get a sweet place to live and thrive. 

The vast majority of land plants form some type of mycorrhizal relationship in their soil. Odds are that when you bought your plant, it already had fungi in and around its roots. However, boosting and promoting these mycorrhizal relationships is one of the best things you can do to support the health of your plant. Mycorrhizal boosters can be added to your soil when repotting or transplanting. Organic fertilizers are great for promoting a diverse and vibrant soil environment, and many of them contain dormant mycorrhizae that will become active when added to the soil.

Some great examples of fertilizers that prioritize the overall health of the plant in this way are BioLive, from Down To Earth, and Bio-Tone, from Espoma. These products and many others are available in our store. 

Magdalen is this week's blog guest writer. Any questions? Submit them through our ‘Contact Us’ tab or email her directly at

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