arbuscular Mycorrhizal Fungi

Arbuscular Mycorrhizal Fungi & Plant Partnership

Hidden from the visible eye is a whole ecosystem of microorganism living in our soil, and arbuscular mycorrhizal fungi are one of the most important.

These mushrooms have a mutualistic relationship with the plants which we love to grow and eat. But don’t expect to eat most mycorrhizae like a fruiting mushroom, because they are in the roots of the plant. There is one exception, and it’s delicious. Scroll down to find out!

We cover what are mycorrhizal fungi, including arbuscular mycorrhizal fungi, and why are they important for your garden, and more importantly your plants!

The Mushroom that will supercharge your plants!

Endomycorrhizal Fungi

Like humans, plants need nutrients to survive and thrive, only plants get their nutrients from the soil. When soil conditions are not optimal, such as slightly acid conditions, cold temperatures and low nutrient levels (phosphorous and nitrogen), plants have a hard time growing and producing, resulting in stunted growth and low crop yields. Not good.

This is where arbuscular mycorrhizal fungi can save the day!

How Do Mycorrhizal Fungi Benefit Plants?

Endomycorrhizae, the most common type of mycorrhizal fungi, help feed plants. In the garden, the mycorrhiza intercepts the roots, and move in. Hence the word “endo”, which Greek for “within”. The plants benefit the mycorrhizae by feeding them sugars in the form of carbohydrates.

In turn, the endomycorrhizae go out and intercept and transform nutrients, making them available to the plants. The fungi basically invades (in a good way) the plant root, and grow from inside the plant cells to act as extensions of the plant root systems.

What’s the Difference between Endomycorrhizae and Arbuscular Mycorrhizae?

Mycorrhiza form a symbiotic relationship between the fungi and the plant roots. The fungi form small structures known as arbuscules, which are the site of transfer of nutrients from fungi to host plant, thus allowing more extraction of nutrients from the soil for both the fungi and the plants.

The most common type of endomycorrhizae is arbuscular mycorrhizal fungi, commonly referred to without the “arbuscular” terminology as “mycorrhizal fungi”. It’s also known as VAM.

Benefits of Mycorrhizal Fungi:

  • Better and more robust growth
  • Improved communication between plants (sharing resources)
  • Healthier, denser root systems with improved ability to get nutrients from soil
  • Richer and denser fruits and vegetables
  • Lower need of watering and fertilizing
  • Higher resistance to drought
  • Decreased stress during transplanting
  • Stabilization of surface
  • Protection against some soil pathogens and diseases

Endomycorrhizae vs Ectomycorrhizae Fungi

There are two types of mycorrhiza: (1) endomycorrhizae and (2) ectomycorrhizae, and both are commercially available to give your plants a boost. Arbuscular mycorrhizal fungi is a type of endomycorrhizae. One other synonym, marketed commercially, is Vesticular Arbuscular Mycorrhizae, otherwise known as VAM or AM Fungi.

Ectomycorrhizae

Ectomycorrhizal fungi do not penetrate their host’s cell walls, hence the “ecto”, which is Greek for “outside”.

The most famous ectomycorrhizae, which is large enough to eat, is the ever so delicious truffle.

On the dark side, deadly death caps and destroying angels (Amanita) ectomycorrhizae are reasons why mushrooms sometime get a bad rap.

Endomycorrhizae

The endomycorrhizae enter the root cell wall and don’t form fruiting structures such as the truffle.

Mycorrhizal Fungi
Arbuscules are inside (endo) the plant roots

Which Plants Benefit from Mycorrhizal Fungi?

Ectomycorrhizae are most associated with trees in temperate and semi-arid regions.

Ectomycorrhizae form on the roots of around 2% of the world’s plants (usually woody), including the birch, dipterocarp, myrtle, beech, willow, pine and rose families. So if you have a rose garden, this is for you!

Roses & ectomycorrhizae need each other

Endomycorrhizae are the most common and widespread fungi, and include most vegetables and fruits. A whopping 90% of all plants on this planet form relationships with the arbuscular mycorrhizal fungi!

So if you are growing tomatoes, that’s important. Purple potatoes in particular need lots of phosphorous, so be sure to introduce the arbuscular mycorrhizal fungi!

Heirloom tomato - brandywine
Tomatoes benefit from mycorrhizal relationships

Plants That Don’t Like Mycorrhizal Fungi

There are only families of plants that do not form mycorrhizae:

  1. Brassicaceae (cabbage, canola, rape, broccoli)
  2. Chenopodiaceae (sugar beet, beet and spinach)
  3. Amaranthaceae (Amaranth)
  4. Caryophyllaceae (Carnation)

In native plants, the Chenopods such as salt bush (Atriplex) found commonly in deserts of the Western US don’t form relationships with mycorrhiza.

arbuscular mycorrhizal fungi and beets do not get along
Mycorrhizal fungi & beets don't get along

Introducing Arbuscular Mycorrhizae Into Your Garden

Inoculation

The endomycorrhizae are hidden partners with garden vegetables, but must be introduced. Most commercially available starters (tomatoes, peppers, corn), as well as seed, do not come pre-inoculated. The mycorrhizal product must be introduced at the beginning of the season.

Dusting Roots | Potting Mix

The simplest way to form the mutualistic relationship is to dust the roots or the seeds with the mycorrhizal inoculum at the time of planting.

Also, consider adding it in your potting mix, or in finished compost.

10X The Nutrient Availability

When the fungi become embedded in the root, nutrient absorption can be 10 times better than an uninfected plant due to the larger nutrient absorbing surface provided by the fungi. Their arms (technically called hyphae) can extend 3 inches beyond the actual roots, allowing more surface area and absorption of nutrients. This will help your tomato varieties produce more fruit, and be healthier overall!

What Nutrients Can Arbuscular Mycorrhizal Fungi Bring to the Plant?

Mycorrhizal inoculant, when introduced is most useful to the plant, particularly when in comes to phosphorous uptake. It helps find the following nutrients:

Phosphorous (P)

Calcium (Ca)

Potassium (K)

Iron (Fe)

Magnesium (Mg)

Zinc (Zn)

Copper (Cu)

Manganese (Mn)

The presence of this arbuscular mycorrhizal fungi also is known to enhance nitrogen fixation in legumes. Believe it or not, they help plant communication too!

Mycorrhizal Fungi Products For Sale

Commercially produced endomycorrhizae and ectomycorrhizae are available for sale. Some commercially available products contain both fungi types in mix and are marked on the package. They are marketed in the following ways & forms:

VAM or AM Fungi

Ecto- and Endo- mycorrhizal inoculant

Ectomycorrhizae for plants

Mycorrhizal fungi

Granular or Powder

Micronized (water soluble)

Liquid

Mixed with other additives

What to Look for In Commercial Mychorrhizal Fungi

For garden vegetables, commercially available mycorrhizal inoculant for sale are generally in the Glomus genus. Glomus intraradices, Glomus mosseae, Glomus coronatum and Glomus etunicatum in many cases come together in a pre-formed mix. These are arbuscular mycorrhizal fungi.

Endomycorrhizae and Ectomycorrhizae
VAM - Arbuscular mychorrizal fungi
Look for the number and type of species as well as propagule count

For garden vegetables, commercially available mycorrhizal inoculant for sale are generally in the Glomus genus. Glomus intraradices, Glomus mosseae, Glomus coronatum and Glomus etunicatum in many cases come together in a pre-formed mix. These are arbuscular mycorrhizal fungi.

What you also might see is species other nitrogen-fixing fungi (not technically mychorrhizal) included in the mix such as species in these families: Azorhizobium, Allorhizobian, Bradyrhizobium, Mezohizobium, Rhizobium and Sinorhizobium. These are free living fungi that fix nitrogen in the soil, which is also beneficial to plants.

Check the Label

When purchasing, be sure to check the label. There are many commercially available products that have only one species. The greater the diversity the better!

Paul Stamet’s Fungi Perfecti offers several mixes. There are a lot available online and we’ve hand selected a few that we love and recommend. If you don’t need ectomycorrizae (using it only for the garden), then don’t bother buying products that have both. However, if you have a rose garden, then they love ectomycorrhizal fungi so get one that has both ecto- and endo-.  If you see a product labeled VAM – that’s the type for the garden.

For Sativa Growers

For Sativa, studies have shown that these species can colonize the roots, so check the packaging for: Diversispora sp., Funneliformis sp., Glomus sp., Funneliformis mosseae, Glomus caledonium, Funneliformis geosporum, Glomus occultum. The colonization by the fungi can differ depending on the hemp cultivar and doses of fertilizers.

Is Mycorrhizal Fungi A Fertilizer?

Technically mycorrhizae is not a fertilizer. It’s a hidden partner that assists plants in obtaining nutrients (fertilizers). One of the greatest benefits from mycorrhizal fungi is the increase in the uptake of phosphates.

Phosphate & Mycorrhizal Inoculant

Studies have found that when there is already a lot of plant-available phosphate, the mycorrhizal fungi isn’t so interested in helping the plant and don’t colonize the roots very readily. This is true for both ectomycorrhizal and endomycorrhizal plants. However this only applies to plant-available forms of phosphorous. Insoluble phosphates are unavailable, and do not affect mycorrhizal colonization.

What this means is if your soils are inherently low in phosphorous, apply rock-phosphorous rather than a synthetic phosphorous (such as Miracle Grow) to have higher inoculation rates.

Application & Mycorrhizal Inoculant

Application rate will depend upon the manufacturer, but it is best to incorporate the mycorrhizal inoculant prior to, or at the time of, planting or seeding so that is can be thoroughly contact the existing or emerging plant roots. You can also mix it with your potting mix, or in finished compost.

The inoculant may either come in liquid form, loose in the mix (granular) or in teabags, which can be inserted into the planting hole, if transplanting vegetables from pots.

How Long is the Mychorrizal Fungi Good For?

Dry formulations of mycorrhizae have a typical shelf life of 16-24 months so check the expiration date on the package. Products that require refrigeration or special handling are not recommended since refrigerated products may have been allowed to get warm and be reduced in effectiveness long before you receive them.

Compare products before you purchase, particularly the number of propagules per gram of the innoculant. The higher the number, the more fungal spores there will be to inoculate the plant roots.

Preferable is to purchase mycorrhizal products that are organically certified. This ensures that the product does not contain any harmful human pathogens, genetically modified organisms or synthetically produced ingredients.

What Else Does Mycorrhizal Fungi Do?

Salt and Toxic Metal Defense

The introduction of mycorrhizal products protect plants from excessive uptake of salts and heavy metals, particularly in western soils where salt content can be high. This is also true for high acid (low pH) soils, which are prevalent in the South.

Promotes Drought Resistance

Mycorriza also have been shown to improve water uptake in soils, making plants more resistant to drought. This is especially important in hot dry soils such as in Arizona, Nevada and Southern California.

Protection from Soilborne Diseases

There is evidence that mycorrhizae protects plants from certain soilborne diseases by producing antibiotics and competing with diseases for infection sites on the roots.

Please note: Many of the mycorrhizal fungi products that we recommend are real recommendations, but the links are affiliate links where we might earn a small commission if you purchase it through Amazon.  This helps cover the cost of running Positively Sustainable. It does not increase the price for you. Thank you for your support!

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Mychorrhizal Fungi is an essential garden mushroom. Why arbuscular mycorrhizal fungi including endomycorrhizal fungi and ectomycorrhize are important for your plant health

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