There’s something you can easily add to your marijuana root zone that stimulates growth, budding, floral development, resin production, and increase harvest weight while also protecting and enhancing your marijuana roots.

This powerful root zone additive consists of beneficial bacteria and fungi that create healthier roots and stoke changes in plant metabolism and structure that lead to stronger plants and heavier harvests of more-potent flowers.

If you’re not adding beneficial microbes, especially if you’re growing in inert root zones such as Grodan rockwool or in water culture, you’re missing out.

Before we explain how to use beneficial microbes, let’s analyze what the root zone really is.

Scientists call part of it the “rhizosphere.” This includes roots, soil directly around the roots, substances exuded by roots, and beneficial microbes that form a symbiotic relationship with roots.

The rest of the root zone is “bulk soil.”

Of course, these definitions assume you’re growing in a solid root zone media such as soil, soilless mix, or coco coir, not in a “water culture” system.

In fact, although water culture systems create faster clone rooting and faster growth, they don’t provide a “natural” rhizosphere.

One problem for growers using water culture hydroponic systems is that root exudates and fragments are washed away, so beneficial microbes have no place to anchor and nothing to feed on.

In contrast, soil, coco, and other solid root zone media can provide a dynamic rhizosphere ecosystem. Nutritional content, porosity, and pH of root zone media greatly determines root health, root mass size, and whether beneficial microbes can work with roots to strengthen plants.

Why Use Beneficial Microbes?

Your plants’ roots produce substances that attract and modify beneficial microbes.

The microbes enhance root size, diameter, and functional complexity, protect roots from drought, cold, pathogenic microbes, heat and other stress, and induce systemic resistance that helps your plants resist all kinds of attacks and stress.

Roots exude sugars, amino acids, organic acids, fatty acids, phenolics, enzymes and flavonoids. Beneficial microbial bacteria and fungi thrive in the rhizosphere when they have access to root exudates, carbohydrates, and aged/dead roots to use as energy sources.

To summarize, beneficial bacteria and fungi can enhance the health of the rhizosphere, creating the following benefits:

  • Beneficial microbes convert otherwise unavailable nutrients into bioavailable forms for easy uptake by plant roots. For example, phosphorus processed by beneficial microbes is more bioavailable to cannabis plants.
  • Beneficial root zone microbes interact with cannabis roots, generating chemicals and hormones that stimulate bud growth and increase potency.
  • Beneficial microbes fight root pathogens by coating root surfaces and triggering systemic disease resistance.
  • Beneficial microbes filter out heavy metals and other contaminants from the soil.
  • When they die, beneficial microbes become nutrition for your cannabis plants.
  • Beneficial microbes interact with roots to alter phytohormonal signaling pathways in cannabis plants, resulting in larger flowers with more cannabinoids and terpenoids, as well as earlier onset of floral buds and earlier maturation of buds.

How to Procure & Use Beneficial Microbes

The common tactic for growers who want the benefits of beneficial microbes is to buy a beneficial microbes product and apply it to the root zone. Some growers concurrently add organic, unsulphured molasses or other carbohydrates to the root zone, as food for microbes.

Unfortunately, there are caveats and problems with this approach. These include:

  • If you’re growing in a hydroponic water culture system such as aeroponics or buckets, added beneficial bacteria and fungi lack rhizosphere physical structure to properly bind with roots. They often bloom in bottom of buckets or hydroponic reservoir, creating an ugly mass that clogs pumps, irrigation tubes and emitters.
  • Because added microbes in water culture have no solid rhizosphere to anchor in, they might not help roots much if at all. Or the microbial bloom may turn foul, creating an anaerobic, pathogenic mess that harms roots.
  • Inert root zone material such as rockwool and coco coir provide a solid rhizosphere that anchors roots and microbes, but these sterile media lack organic carbons and may have pH issues or other characteristics that work against microbial colonization.
  • Growers add carbos to the root zone to feed beneficial microbes, but this must be done carefully, or it can foul the rhizosphere. Most carbohydrate products sold at gardening shops are overpriced; some are useless. Organic, unsulphured blackstrap molasses is much better and more affordable, and has the added benefit of containing iron, a plant nutrient.
  • Using inert media hydroponic systems that rely on timed irrigation, water flows into the root zone and then drains to waste or to a reservoir. Root exudates and debris that feed and/or signal beneficial microbes are often washed away.
  • In soil and soilless mix, rhizosphere structure is usually conducive to microbial flourishing, as long as pH and other factors are favorable. However, synthetic hydroponic nutrients and other chemical fertilizers can harm or even kill beneficial microbes. The types of hydroponic nutrients chelation and formats of nutrients elements, along with incongruous pH traits, can make the root zone toxic for beneficial microbes. This is one reason growers use organic nutrients.

Perhaps the biggest problem for cannabis growers it that most beneficial microbes products sold in gardening stores aren’t very good, most are way overpriced, and some are useless or even harmful.

As you might expect, each plant species has its own ideal set of beneficial microbes that it co-evolved with.

Microbial species that form a perfect bond with the roots of other species might not be useful for cannabis, and vice versa.

Problem is, most manufacturers of microbial gardening products aren’t doing original research with cannabis to find the best microbial species for marijuana roots.

Their products contain a generic menu of rhizobacteria and mycorrhizal fungi that haven’t been sufficiently tested to determine how well they work with cannabis roots.

Another problem with store-bought root zone microbials is that they might not be alive anymore—they die on the shelf.

I’ve seen tests of all the major brands of beneficial microbes sold in gardening stores showing that most didn’t contain the concentration or diversity of species claimed, and several were biologically inert (useless).

Before purchasing any beneficial microbes product, ask the manufacturer the following questions:

  • Can you provide third-party lab test data showing the ingredients and efficacy of your product in cannabis gardens?
  • What original research did you do to determine which microbial species to include?
  • What is the shelf life after opening, and in use?
  • Are there any special instructions regarding water quality, chlorine/chloramines, types of root zones and other cultivation advice?
  • Are there any types of nutrients or supplements that you recommend, and any you recommend against, when using your product?

We asked these questions of every major company that markets a beneficial microbes product to marijuana growers.

The only useful, transparent, science-verified answers we got came from TPS Nutrients, which is based in Seattle.

We’ve written about TPS before, because they make great one-part, all-season base nutrients.

They also make a potent silicon additive and resin enhancing products.

Their beneficial microbes product is called “Billions.” Here’s what they told us about Billions:

“TPS Billions is the most bioactive microbial supplement on the market.  We guarantee more than one billion active colony forming units (CFU) per gram, and all lab analysis samples show more than 1.1 billion CFU per gram.

Billions outperforms every competitor we tested it against.  There are two primary reasons for this.  First, the strains we bred are exceptionally vigorous. For example, for each bacterium we included multiple sub-strains. 

The second reason is that Billions is created with organic turbinado diluent, but all the other products use highly-processed maltodextrin. Billions gives you faster microbial replication because turbinado is a more complete sugar which includes amino acids and molasses.

As an added benefit, turbinado increases solubility to near 100%. This means that using Billions, you don’t have clogged irrigation equipment, or settling of the microbes.

We know Billions is the only purpose-built, third-party verified product designed specifically for marijuana roots. We’ve been testing strains internally and with several third-party microbe testing greenhouses for many years, giving us the data and time to select stellar strains that are highly effective together. 

At one point we had more than 20 strains in testing. We narrowed that down to our existing playlist, because research showed that using a few high-value strains is better than using many mediocre strains.

One major find was that rhizosphere bacteria are 8-10 times more effective than fungi in providing plant growth and yield benefits, which is why Billions is so bacteria heavy versus fungi.

You’re correct to point out that installing beneficial microbes in water culture root zones may cause problems.

Some growers using well-oxygenated hydro systems and tiny amounts of H2O2 or hypochlorous acid have had great results, but novice hobbyist growers often come up against too much of a microbe bloom. 

In our testing facilities we follow strict root zone and reservoir hygiene guidelines and Billions works very well. Of course it works incredibly in soil, soilless mix, coco coir, rockwool and other solid media. Home growers using pure hydroponic water culture systems should talk to us about the best way to use Billions.

Here are our guaranteed ingredients…


Bacillus subtilis……………..145,000,000 cfu/g

Bacillus pumilus…………….145,000,000 cfu/g

Bacillus amyloliquefacien..145,000,000 cfu/g

Bacillus licheniformis……..285,000,000 cfu/g

Bacillus laterosporus………280,000,000 cfu/g


Glomus intraradices……………………4-6 cfu/g

Glomus mosseae……………………….4-6 cfu/g

Glomus aggregatum……………………4-6 cfu/g

Glomus etunicatum…………………….4-6 cfu/g

Harzianum Trichoderma……….200,000 cfu/g”

The TPS science team provided the following Billions info in response to reader questions:

  • Billions can be used starting when clones or seedlings have established root systems, but is not helpful for unrooted cuttings, or seeds that are germinating.
  • If you use too much Billions or too often, the microbes may overprocess nutrients elements, changing reservoir pH or root zone media in ways that aren’t beneficial.
  • Billions used in pure hydroponic systems such as deep water culture might be supercharged by the intense oxygenation those systems provide, creating pH shifts and other problems.
  • Using the TPS Root Boost product with Billions creates a symbiotic boost to root growth and function.
  • Root Boost contains carbon, phosphorus, beneficial bacteria and fungi, humic, fulvic, amino, and other organic acids complexed with extracts from 9 species of sea plants

We’ve tested Billions, and we agree with TPS that they’ve created the most effective rhizosphere booster. It’s powdered, easy to use, affordable, and visibly works–we see increase in root mass and health when we use Billions.

Two other important things for you to know:

  • Making compost is a great way to get microbially-rich material for your root zone.
  • Using hydrogen peroxide (H2O2) as a disinfectant, oxygenator or cleaner in your root zone kills beneficial microbes. Chlorine and chloramine found in most tap water also kills beneficial microbes.

The bottom line is: if you have two marijuana gardens with everything identical except that one set of plants has a healthy rhizosphere with Billions beneficial microbes added and the other one doesn’t, the plants growing with TPS Billions have faster growth rate, earlier flowering, faster finishing, heavier buds, and more cannabinoids and terpenoids.