The marijuana root zone is the physical foundation of cannabis plant health, metabolism, and productivity.

In Nature, marijuana roots are part of a co-evolved ecosystem that protects them and enhances their function, fueled by plant growth-promoting microbes (PGPM) and plant growth-promoting rhizobacteria (PGPR). These living organisms can be used by marijuana growers as “bioinoculants.”

PGPM produce substances that promote plant growth by increasing availability and uptake of nutrients in soil via phosphate solubilization, siderophore and indole-3-acetic acid production, nitrogen fixation, and suppression of plant pathogens.

PGPR increase plant growth rate and nutrients absorption—especially when plants are under stress from drought, heat, overfeeding or underfeeding, and pathogenic attack. They bind with roots using arbuscular mycorrhizal fungi (AMF) to increase root surface area, leading to increased, more-rapid nutrient acquisition.

Specific types of bioinoculants are useful from germination to harvest, and especially for getting seedling, clones, and transplants off to a great start.

Unless you’re growing outdoors in native soil with a soil ecosystem that evolved to include specific PGPM and PGPR species beneficial to marijuana roots, you only get root benefits when you add quality, science-based bioinoculants.

Growers see a confusing array of different brands of these products, with each brand claiming to have PGPMs and/or PGPR that work for marijuana roots.

Unfortunately, as with so many other product niches in the marijuana cultivation supplies industry, there are big problems with most of these brands and their products, including:

  • They’re not manufactured properly.
  • They don’t contain the right species or any species at all
  • They aren’t “live in the bottle.”
  • They’re very expensive, and don’t give you sufficient return on investment.
  • They can cause huge messy problems in pure hydroponics systems such as water culture and in hydroponic reservoirs.
  • Organisms have a hard time “colonizing” your cannabis roots when you’re using inert root zone media such as rockwool, and in water culture systems.

A successful microbial inoculant has to colonize external and internal parts of root tissues to establish a symbiotic interaction with roots. It must also successfully, persistently compete against other microorganisms, especially root pathogens.

Moreover, even if bioinoculants plant initially colonize the cannabis root zone, their continued effectiveness and longevity aren’t always guaranteed. In many cases, bioinoculants when first applied are vigorous and effective, but soon die off due to environmental factors and/or pathogens.

What’s more, some beneficial microbes should only be used early in your plant’s life, while others are best used only during bloom phase, but most companies that sell these products don’t know that.

Scientific testing to measure cannabis root zone health and bioinoculant efficacy is an emerging research field, not yet as precise and reliable as it should be, but science does show specific breeds of Pseudomonas, Bacillus, Azospirillum brasilense, Gluconacetobacter diazotrophicus, Burkholderia ambifaria, and Herbaspirillum seropedicae species have root zone effectiveness leading to increased rooting, transplant success, growth rate, nutrients absorption, harvest weight, potency, and desirable cannabinoid profiles.

Bioinoculants can also be used as a cannabis foliar spray to attack Botrytis cinerea (gray mold/bud rot) and Trichothecium roseum pathogens commonly found on cannabis plants, especially outdoors. These pathogens damage leaves, flowers, stems and branches.

Indoor cannabis plants are also harmed by Golovinomyces, which causes powdery mildew (PM). PM is a severe fungal disease that ravages leaves and buds, and is often seen in indoor cannabis production.

Some marijuana growers use foliar fungicides, sulfur, bicarbonates, horticultural oils and other substances to fight powdery mildew and botrytis, but these sprays always cause at least minor harm to plants and are not safe (or pleasant to taste) on mature buds. Spraying anything on plants after buds are developed INCREASES the risk of bud rot.

Adding pure humic acid to root zone feeding with Bacillus subtilis and Pseudomonas aeruginosa has been shown to potentiate bioinoculant effects leading to increased nutrients absorption and production of beneficial root zone compounds.

Some growers believe adding molasses or other sugars to the root zone feeds bioinoculant organisms. This could be true, but also can quickly lead to a toxic root zone that provides ideal habitat for pathogenic microbes and/or pests.

I personally tested 17 different powdered or liquid bioinoculants brands marketed to cannabis growers, but never saw positive difference in root mass, root health, or plant health between plants without the bioinoculant versus those given bioinoculants.

About half of the liquid products were foul-smelling and spoiled, even though the official shelf life was “not expired.” When I asked manufacturers of those products for third-party scientific proof their products contain the right microbial species for cannabis, are bioactive on the shelf and after opening, and produce the claimed benefits, most refused to provide any or sufficient information. And some were openly hostile to being asked to provide proof.

The only manufacturer who provides scientific proof of their products’ ingredients and effectiveness is Xtreme Gardening.  Xtreme Gardening is legit because it’s a subdivision of Reforestation Technologies International (RTI), North America’s oldest manufacturer of Mycorrhizal Inoculum.

RTI soil treatment products are used in forestry plantations in nearly a dozen countries.

Although skeptical when I first used Xtreme Gardening root zone products, due to previous failure of competing brands, I saw faster growth, better nutrients absorption, healthier plants, and fatter yields associated with successful root inoculant treatment.

Indeed, Mykos WP is so effective that root growth is way faster than usual, and way more dense, so I had to transplant sooner, and use larger finishing containers.

Before I found out from Xtreme’s very helpful product support team that Mykos WP is best used only in grow phase, to be followed with other Xtreme products best used only in bloom phase, I used Mykos WP several weeks into bloom phase. I stopped only after seeing such explosive root growth that healthy white roots were extending 4-7 inches from the bottom of my plant pots, in 7-10 gallon containers with Pro Mix HP.

I knew for sure that Mykos WP was responsible for these super-roots, because this only happened when I used Mykos WP well into bloom phase, and had never happened before under any conditions or using competing brands.

Mykos WP really is rocket fuel for marijuana roots! And the great news is, the better the roots, the better your cannabinoid/terpenoid potency, finishing times, and yield!

So far, Xtreme Gardening is the only brand of marijuana root zone beneficial microbes products that has worked so obviously and effectively.

I recommend three Xtreme products, and am waiting for more information from Xtreme, and more testing, so I can expand my recommentations. Use these products:

  • MYKOS WP. This wettable powder contains the arbuscular mycorrhizal fungi Rhizophagus intraradices, formally known as Glomus intraradices. MYKOS does not contain any other microbes such as trichoderma or ectomycorrhizae.
  • AZOS® is an all-natural, growth-promoting, Nitrogen-fixing bacteria ideal for cloning and transplanting.
  • VERSITY Bacillus Blend is a dry blend of multiple Bacillus bacteria species, enhanced with kelp and humic acid that promotes beneficial microbes, root growth, breakdown of organic materials, nutrients cycling, and solubization of phosphorus and potassium.

You may have heard that “compost tea” benefits your cannabis root zone due to bioinoculants on-board. I used several different starter kits and organic tea-making methods, but saw no benefits, and later found studies showing compost tea has no positive influence on cannabis root zone bacterial diversity, root health, or plant performance.

Be aware that some bioinoculant products create harmful blooms in hydroponic reservoirs and systems, and water containing chloramine and/or chlorine (found in almost all municipal tap water) kills beneficial root zone microbes.

Further, in most pure hydroponics systems and sterile root media such as rockwool, beneficial microbes aren’t able to anchor properly.

Ask about Xtreme root zone inoculants at your local cultivation store or contact Xtreme direct. The root zone and plant benefits of PGPMs and PGPRs are well worth the cost of Xtreme Gardening products. If the store doesn’t carry Xtreme, tell them they should:)