Mycorrhizal fungi, or mycorrhiza, are beneficial fungi that live in symbiosis with plants. In order for this symbiosis to take place, there must be direct contact between plant roots and the fungus. Applying early on you can see the difference in plant vigor and growth.

The benefits of mycorrhiza continue to prove themselves throughout plant evolution. Nearly 400 million years ago when plants moved from the ocean to land, they did not have a root system. Plants relied on fungi in order to absorb crucial nutrients and water for survival. These fungi were the plant’s root systems before plants actually developed root systems themselves.

This symbiotic relationship continued well after plants had established root systems. Some plants even require mycorrhizal fungi to grow optimally; this is known as an obligate mycotrophy. While cannabis can grow without mycorrhizal fungi, it is widely considered an obligate mycotroph, which means partnering with these fungi will certainly contribute to maximizing the plant’s genetic potential.

 I wanted to bring you more insights into this fascinating world of mycorrhizal fungi and sat down with the team at DYNOMYCO™ Inoculants in order to better understand this plant-fungal symbiosis and why fungi are so important for cannabis growers. Before we get into that let’s get a better understanding of what mycorrhizae actually are.

Understanding Mycorrhizae

The earliest evidence of this plant-fungal symbiosis dates back 407 million years and is known as mycorrhiza, which in Latin literally translates to fungus root (myco = fungus and rhiza = root ).

 There are five types of mycorrhizal fungi on the planet that are currently known to scientists. Each plays a key role in nature, associating with only specific plants at times and at others with a wide array of plants. Only one is beneficial to cannabis and that is the arbuscular mycorrhizal fungi (AMF) and within this category even fewer actually associate with cannabis.

AMF is the most common of all fungi and is associated with approximately 90% of all plants on earth. These fungi literally penetrate cell roots and create a network within the root and outside of it. The fungus creates a branching structure, an arbuscule, within the plant cell where carbohydrates from photosynthesis are exchanged for nutrients, water, and minerals brought by the fungi. These fungi do not produce any fruiting bodies and reproduce asexually below ground. 

This symbiotic relationship is fairly simple. The plant supplies the fungi with carbohydrates and in return, the fungus provides the plant with the necessary nutrients it needs. The more the plant needs nutrients the more carbohydrates it will send down to the fungi. With cannabis plants, this exchange is done inside the cell root in the arbuscules.

Cannabis Co-Evolved With Fungi

Before the legal changes that began in 1996, most cannabis cultivation was done indoors and away from the eyes of neighbors (unless you were in Humboldt county). Growers relied heavily on technological advances in lighting, ventilation, and various hydroponics systems.

Growing was done indoors and not out in the open; growers relied on bagged growing media for their substrate. The majority of packaged growing media arrives at our doorstep after being sterilized. “Kill off all the bad guys along with the good guys and feed the plants the essential NPK and a few other microelements and you’ll be good” was the approach that many growers used. There’s been a shift in thought over recent years and many growers are now leaning towards a living soil method by using the soil food web and taking advantage of the various microbes in the soil. As Jeff Lowenfels’ books suggest, we need to be “Teaming with Fungi” and “Teaming with Microbes” and the reason is simple. Nature knows what to do best. Mimic it and you’ll get promising returns.

When cannabis was illegal, no real scientific studies and trials were done on the efficacy of the growing techniques and methods in terms of what affects the plants and the phytochemicals, terpenes, cannabinoids, and flavonoids. With the advances of science and the fact that cannabis is now legal in many states, more and more growers have the opportunity to dive into real scientific research. One of these fields of research is the soil science aspect and the delicate interaction between plants and the soil microbes in which the plants grow.

The Benefits of Mycorrhizal Associations

There are many benefits of utilizing fungi in your cannabis garden. Firstly, a larger root surface allows the plant to absorb nutrients, minerals, and water from a greater area. In nature, the mycelial network can extend for miles and connect between multiple plant species! A larger root surface area will help in many things, amongst them is transplant shock and death rates which are much lower when mycorrhizae are present compared to when there is no symbiosis.

Secondly, there is increased nutrient uptake. With an increased surface area, plants can now absorb more nutrients and water than without the mycorrhizal association. This means reduced fertilizer inputs and higher yields. In addition, the AMF not only helps with the basic NPK but also with the absorption of microelements such as iron, zinc, and manganese.  

Other benefits include Increased phosphorous absorption. Mycorrhizal fungi secrete unique enzymes that free up phosphorous molecules and transport them to the plants in an available form. This is especially beneficial since roughly 85% of phosphorous in the soil is unavailable for plants. Once it’s flower time and fertilizing program changes, nitrogen levels go down and phosphorous levels go up in order to increase the size of the buds. With the help of mycorrhizae, the plants will already be enjoying increased phosphorus levels compared to non-inoculated plants.

Using fungi also creates a living rhizosphere. Life brings life, it’s as simple as that. When adding a biological element to a growing operation it tends to create more life. The addition of mycorrhizae will help other microbes thrive, for instance, bacteria. The hyphae literally create a superhighway for the bacteria to move around on. These bacteria also play pivotal roles, from nitrogen fixation all the way to plant protection. This living rhizosphere creates a new ecosystem where all the organisms benefit from the presence of one another and help each other compared to a lifeless inert media with only synthetic inputs added.

Fungi can also serve as a defense mechanism. With the help of this hyphal network surrounding the roots, plant pathogens have a much harder time attacking the plant. Research has shown that mycorrhizal fungi can help combat certain soil-borne pathogens, amongst them are Fusarium, Pythium, parasitic nematodes, and others.

Plants with a mycorrhizal association have a higher stress tolerance because the presence of the fungi lowers the salinity (EC) of the soil and therefore affects the pH and EC levels making the soil more suitable for plants to live in. In addition, the plants are more drought-tolerant because mycorrhizal plants are able to “reach” larger distances in search of water. The hyphae extend well beyond the rhizosphere and spread out into areas that plant roots can’t access. 

Finally, mycorrhiza also produces glomalin, which is a glue-like component secreted by the fungi that help bind soil particles together to prevent soil erosion as well as improve soil stability. Scientists are seeing a correlation between the presence of glomalin and the primary productivity of an ecosystem. It is the foundation of all ecosystems so to speak and the absence of fungi will create an imbalance in the entire ecological system. If you are attempting to grow in a no-till, regenerative approach, mycorrhizal fungi should be the first thing to add to your garden. 

Application of Mycorrhizal Fungi

 There are several ways to introduce mycorrhizal fungi to your grow operation. The earlier in the plant’s life the better, the simpler the application and the higher chance for successful inoculation. The younger the plant is, the greater the impact of mycorrhiza. As the plant matures, the tougher it is to guarantee inoculation. The older the roots are, the more they thicken and harden, making it difficult for the fungi to penetrate. Since the fungi must reach young, penetrable roots that are found at the bottom of the pot or at a greater distance from the stem, the application is more complex and the impact much lower than with young plants. Below are several of the application methods we recommend using.

1.     Mixing your inoculant into the growing media: This method of inoculation is simple and very convenient. Apply the product at the rate on the label, mix it uniformly into your media and you’re good to go. This method assures you that the fungi is spread out in

the soil and will be in close proximity once the roots grow out in search of food. If working in a large-scale facility, a soil mixer saves time and is ideal for mixing, especially if you’ve got thousands of plants.

2.     Planting hole application: If you transplant your plants, apply mycorrhizal inoculants at every transplant. Simply place your inoculant at the bottom of the planting hole at the recommended rates and you’re done. This will help reduce transplant shock.

3.     Rootball dusting/coating: This is done when your plant is ready to be transferred. Place some of your inoculants in a large enough container to fit the rootball of your plant. Wet your soil a bit, then roll the rootball in the inoculant so that it covers the sides and bottom uniformly. Another option is to sprinkle it onto the wet rootball if you want to conserve the product.

There are many ways to grow cannabis, and many inputs you can add to the mix. The addition of mycorrhizal fungi to your growing media should be a staple regardless of the fertilizer or input you use. This, in turn, will result in benefits that can be easily identified and clearly seen.

Mycorrhizal Fungi and Sustainable Agriculture

 With the addition of mycorrhizal fungi and the increased ability to absorb nutrients and water, many times a reduction in fertilizer usage and watering can be attained. The team at  DYNOMYCO™ researched trials on various plants including cannabis, where, through the use of fungi, fertilizer rates were reduced by 30%, and at the same time yields have increased of 25-30% compared to the standard 100% fertilization program. This is especially important since current agricultural and growing practices rely mostly on synthetic and mineral fertilizers. These minerals have to be mined from various rock formations around the world and are declining rapidly, most notably, phosphorous. Phosphorous is mined from phosphate rock, which scientists believe will reach peak levels in 2030, and afterward, the production will decline until we run out of it completely. The top five phosphorous producing countries produce approximately 90% of the world’s entire supply. Approximately 90% of the phosphorous given to plants remains locked in the soil, bound to either calcium (Ca) ions in calcareous high pH soil or to iron (Fe) and aluminum (Al) oxides at low pH. Therefore, the implementation of mycorrhizal fungi in soils is important not just for increasing yields and for healthier plants, but for better use and efficiency of our entire agricultural system.

 This video shows the dramatic difference early inoculation with Mycorrhizal Fungi makes.

5 Known Types of Mycorrhizal Fungi 

 Arbuscular mycorrhizal fungi (AMF): The most common of all fungi. AMF associate with approximately 90% of all plants on earth. These fungi literally penetrate cell roots and create a network within the root and outside of it. The fungus creates an arbuscule within the plant cell where carbohydrates from photosynthesis are exchanged for nutrients, water, and minerals brought by the fungi. These fungi do not produce any fruiting bodies and reproduce asexually below ground. 

Ectomycorrhizal Fungi (ECM): This group of mycorrhizal fungi associate with around 5% of plant species on the planet, mainly with hardwood trees such as Birch, Oak, Pine, Douglas Fir, and others. ECM surround the roots of plants but do not penetrate them like AMF and the exchange between fungi and host is different. ECM reproduce sexually via fruiting bodies, better known as mushrooms. Examples of these are the culinary delicacy truffles and porcini and the infamous Amanita mushrooms. It’s important to note that ECM does not associate with cannabis plants as they are not hardwoods.

Orchid mycorrhizae: The name gives it away. These fungi associate only with the Orchidaceae family and play a very important role at the germination stage when the young plant requires carbon provided to it by the fungus.

Ericoid mycorrhizae: These fungi are found in acidic and nutrient-poor soils such as heathlands, bogs, and forests. This group of fungi has the ability to breakdown organic forms of nitrogen which can be limited where large quantities of ericaceous plants are found. These fungi are found on almost all continents except for Antarctica.

Monotropoid mycorrhizae: These fungi associate with plants that rely solely on the mycorrhizal association as their carbon source. This type of fungus, as well as these types of plants, are found in coniferous/mixed coniferous forests with very little low light levels.

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