Many home growers are already familiar with the term mycorrhiza, but just in case you aren’t, here is a refresher: Mycorrhiza refers to the symbiotic relationship that forms between beneficial fungus and a plant’s root system. Utilizing a cultivation system that fosters mycorrhizal associations, which allow for greater nutrient uptake by the plant, will undoubtedly result in a more bountiful harvest.

At the heart of the mycorrhizal association lies a symbiotic relationship between fungal spores and the plant’s root system. This relationship is a form of mutualism. Mutualism occurs when two or more species interact in such a manner that their relationship benefits the health and well-being of both organisms. In certain situations, the relationship becomes one of dependence, with each part needing the other in order to survive. This is just one of many symbiotic relationships found in nature that contribute to our ecosystem. Each link in the chain is equally as important as the next.

There are two types of mycorrhizal fungi—endo and ecto. The vast majority of beneficial fungi fall into the endomycorrhizal category, which has several subclasses of its own. Of those subclasses, the Arbuscular type constitutes around 80 per cent of all mycorrhizal associations. These Arbuscular, or AM endomycorrhizae, grow into the root system, penetrating its outer layers. They then branch outward into the soil extracting and converting nutrients.

The nutrients are then fed into the roots by means of these beneficial fungi. In nature, this process is largely responsible for facilitating the process of photosynthesis. Ectomycorrhizae are the least common form of mycorrhizae, attributing for around two per cent of mycorrhizal associations in nature. They differ in as far as instead of penetrating the root, they wrap around it to form a protective sheath. These types of associations are more often found in harsh climates.

Many growers who cultivate indoors use nutrient or mineral salts to fertilize their plants. There is nothing wrong with that. You will get good, standard results growing this way. However, nutrient salts and natural fungi in soil don’t mix. Now, if you are growing great plants and don’t see a need to change, you should know a few things.

Nutrient salts will always result in a lower nutrient bio-availability than other cultivation methods. Nutrient salts typically result in a nutrient bio-availability of around 25 per cent. Bio-availability refers to the amounts of nutrients that are in a state readily available for absorption. The use of nutrient salts and mycorrhizae are unfortunately mutually exclusive. Many of the salt-based nutrients today will kill or disrupt the function of mycorrhizae.

In order to foster a mycorrhizal association in your soil, you will want to use organic, or better yet, veganic cultivation techniques to get best results while simultaneously shifting to a more natural style of growing. We should all be familiar with the basic concepts of organic cultivation. In this day and age when we are discovering the damage that pesticides can do to the environment and delicate ecosystems, we should all be looking to make the switch.

When you are cultivating organically, you are using nutrients based on naturally sourced things like seaweed and animal manure. Organic nutrients tend to come from renewable resources and are environmentally friendly. The one thing they fail to do is naturally provide sufficient quantities of the mycorrhizae you need. This is not really a big deal as you can purchase mycorrhizae for supplementation.

Here’s the kicker with organic cultivation: While it is leaps and bounds ahead of fertilizing with nutrient salts, it has its limitations. When you garden organically, the animal manure leaves behind trace elements, which can be subtly detected in taste if you know what you are looking for. Organic gardening results in a nutrient bio-availability of around 50 per cent. That’s good, but not great. Also, there is the need to continually supplement your root systems with mycorrhizae—the extent of which you are required to do so is debatable (see sidebar).

So, if you want to benefit from a mycorrhizal association between your root system and soil, what’s the best way to go about it? The short answer is veganic cultivation, which is a method of growing that simply looks to make the most of your garden by nurturing a mycorrhiza-friendly environment. The biggest goal veganic growers have is to produce a micro-ecosystem that will not only allow for healthy growth of beneficial fungi, but for bacteria and other microbes as well.

The main source of nutrients in a veganic garden is a good, old-fashioned compost typically comprised of greens mixed with animal manures and sometimes even eggs. In a veganic compost, you’re just going to skip the animal products and stick with as much decaying plant matter that you can get your hands on.

A tea made from compost is the best natural fertilizer for fostering microbial and particularly mycorrhizal associations in your soil. A good compost tea takes a while to prepare. It starts with a huge pile of dead, rotting plants. Over time, as your compost begins to decompose, it will attract a slew of insects, worms, flies and beneficial fungi that will go on to form the mycorrhizal relationship with your roots.

As the pile decomposes, the larva and other creatures that have found a home in your compost will digest the plant matter and in turn excrete raw elemental nutrient. These nutrients will in turn be converted by the mycorrhizal fungi into a form that is more readily available for the root system.

It should be no surprise that by using a veganic method of cultivation geared toward fostering a healthy mycorrhizal network, you will achieve nearly 100 per cent nutrient bio-availability. This is the highest degree of nutrient absorption of any method of cultivation that uses a soil-type medium.

Understanding the importance of mycorrhizae and how to foster mycorrhizal relationships in your soil is the first step in moving toward a more natural garden. Making the switch to a cultivation method that embraces natural ecosystems as opposed to artificial supplementation will result in increased nutrient bio-availability and overall greater yields.


Mycorrhizae Q&A

Q: If I use mycorrhizae when I start seeds, do I have to use it with every transplant?

Matt says: The short answer is, once a plant is inoculated with mycorrhizal fungi you do not need to keep applying the mycorrhizal products. The catch that you may run into is that inoculating from seed is tricky. The key is the placement of the mycorrhizal product. I would suggest applying a layer of the product well below where the seed is planted such that as the roots emerge from the seed, they must travel through the mycorrhizal product layer. Only by doing this can you ensure a higher chance of inoculation. An option you may want to try is germinating the seed, and then prior to the first transplant into a larger container, use the mycorrhizal product to dust the roots. This is a highly effective way to inoculate the plant. As I stated above, once you’ve done this, you do not need to re-apply the mycorrhizal product.

– Matt Linderman, Santiam Organics President & CEO

Andrew says: I’d say once upon transplanting, and good to apply once every two weeks after that. This ensures that the proper species dominate the microflora of the root zone. If your microbial product contains nitrogen-fixing bacteria, discontinue the applications in the second half of flowering.

– Andrew Schell, House & Garden Nutrients International Sales Manager