Azos nitrogen fixing bacteria is a key part of successful indoor growing — here’s exactly what it is and how it works. Azos is a natural, biological root inoculant developed by Xtreme Gardening — one of the most trusted names in plant science-backed growing products. At its core, it’s a concentrated population of a beneficial nitrogen-fixing bacterium called Azospirillum brasilense, which forms a symbiotic relationship with plant roots to support faster establishment, more vigorous vegetative growth, and better overall plant health.
It works differently from conventional fertilisers. Rather than supplying nitrogen directly from a bottle, Azos introduces living bacteria that convert atmospheric nitrogen — which makes up approximately 78% of the air we breathe — into a plant-available form at the root zone. The result is a natural, continuous nitrogen supply that supports growth without the risk of chemical burn or salt accumulation.
What Does Azos Actually Do?
Nitrogen fixation
The Azospirillum brasilense bacteria in Azos fix atmospheric nitrogen and convert it to ammonium — a form plants can absorb and use directly. This process supplements your main feeding programme and can meaningfully reduce the amount of nitrogen fertiliser your plants need, particularly during the vegetative stage.
Root development
Azos produces natural plant growth hormones — particularly indole-3-acetic acid (IAA), a type of auxin — that stimulate lateral root development. This produces a denser, more extensive root system, which in turn improves nutrient and water uptake from the growing medium. For cuttings and seedlings, this effect is particularly valuable. A cutting that establishes roots quickly has a head start that compounds throughout the grow. Growers regularly report faster rooting times and more uniform root development when Azos is applied at the propagation stage.
Stress resistance
Azospirillum bacteria also produce compounds that help plants cope with environmental stress — including drought stress, transplant shock, and temperature fluctuations. Plants treated with Azos tend to recover more quickly when conditions are less than ideal.
How to Use Azos
Azos is a powder product, straightforward to apply at several stages of the growing cycle.
For cuttings and seedlings
Mix 4 tablespoons (approximately 60ml) of Azos per gallon (4.5 litres) of water to create a solution. Soak your grow plugs or Rockwool cubes in this solution for 10 minutes before use. Before inserting a fresh cutting, dip the cut tip into a paste of 1 part Azos powder to 2 parts water for 15 seconds. This direct inoculation at the cutting site gives the bacteria immediate access to the developing root zone.
For transplanting
When transplanting seedlings or rooted cuttings into their final growing medium, dust the root ball lightly with dry Azos powder, or water in with an Azos solution at the point of transplant. This minimises transplant shock and supports rapid root re-establishment in the new medium.
As an ongoing supplement
Azos can be incorporated into your regular feeding schedule throughout the vegetative stage. Add it to your watering solution at approximately 2 tablespoons per gallon of water. The bacteria continue to colonise the root zone and fix nitrogen as long as conditions remain favourable — adequate moisture and temperatures between 15–30°C.
How quickly does it work?
The bacteria in Azos begin working within 20–60 minutes of application. Visible effects — faster root development in cuttings, stronger early vegetative growth — are typically apparent within the first 1–2 weeks of use.
Is Azos Compatible With My Growing Setup?
Azos is compatible with most growing systems and media:
- Soil: works particularly well in organic growing media, where the bacterial populations integrate naturally with the existing soil ecosystem
- Coco coir: highly effective — the bacteria colonise readily in well-aerated coco/perlite mixes
- Rockwool and inert media: best applied at the propagation stage via a solution soak
- Hydroponic systems: Azos can be used in hydroponic setups, but bacteria populations in a recirculating system may be less stable than in substrate growing. Best used during propagation and early establishment phases.
Azos works well alongside other Xtreme Gardening products — particularly Mykos, their mycorrhizal inoculant. Azos supports nitrogen fixation and early root stimulation; Mykos extends root reach and improves phosphorus uptake. Together they address two of the most important root-zone biological processes simultaneously.
Is Azos Safe?
Yes. Azospirillum brasilense is a naturally occurring soil bacterium found in agricultural soils around the world. It is not harmful to humans, animals, or the broader soil ecosystem. Azos contains no synthetic chemicals, is registered for use in organic growing systems, and carries no hazard classifications under standard UK/EU labelling. It can be used safely alongside most nutrient lines and supplements, though it’s best to avoid applying Azos at the same time as products containing high concentrations of hydrogen peroxide, as these will kill the bacteria.
Azos vs Synthetic Nitrogen Fertilisers
Azos is not a replacement for your main feeding programme — it’s a biological complement to it. Conventional nitrogen fertilisers supply nitrogen immediately in a readily available form; Azos supports a sustained, natural nitrogen input through bacterial fixation. The two approaches work well together.
The practical advantage of Azos over relying entirely on synthetic nitrogen is in the root zone: you can maintain healthy nitrogen levels for your plants while reducing the overall mineral salt load in the growing medium. This lowers the risk of salt accumulation, reduces the frequency of flushing needed, and contributes to a more balanced root environment over the growing cycle.
Frequently Asked Questions
Azos has a shelf life of approximately two years from the date of manufacture when stored in a cool, dry place away from direct sunlight. Keep the lid firmly closed between uses to prevent moisture ingress, which can reduce bacterial viability over time.
Azos is compatible with most mineral and organic nutrient lines. Avoid applying it simultaneously with strong oxidising agents or products with very high copper or zinc concentrations, as these can be bactericidal. As a general rule, apply Azos in plain pH-adjusted water rather than mixing it directly into your full nutrient solution.
Azospirillum bacteria are most active between 15°C and 30°C. Below 10°C, bacterial activity slows considerably. In UK growing conditions, this is rarely an issue in an indoor growing environment with adequate heating, but worth being aware of if using Azos in a cold greenhouse or outbuilding in winter.
Yes — the two products are designed to be used together and address complementary aspects of root biology. Apply both at transplant and during the establishment phase for maximum effect. Mykos mycorrhizal fungi extend root reach and improve phosphorus uptake; Azos bacteria fix nitrogen and stimulate lateral root development. They do not compete with each other.
Azos is available in several sizes to suit different growing scales — from smaller 2oz trial sizes through to larger 12oz and 6lb containers for commercial growers. For most home growers, a 2oz or 6oz container will last one to two full growing cycles used as directed.
It works differently from conventional fertilisers. Rather than supplying nitrogen directly from a bottle, Azos introduces living bacteria that convert atmospheric nitrogen — which makes up approximately 78% of the air we breathe — into a plant-available form at the root zone. The result is a natural, continuous nitrogen supply that supports growth without the risk of chemical burn or salt accumulation.
What Does Azos Actually Do?
Nitrogen fixation
The Azospirillum brasilense bacteria in Azos fix atmospheric nitrogen and convert it to ammonium — a form plants can absorb and use directly. This process supplements your main feeding programme and can meaningfully reduce the amount of nitrogen fertiliser your plants need, particularly during the vegetative stage.
Root development
Azos produces natural plant growth hormones — particularly indole-3-acetic acid (IAA), a type of auxin — that stimulate lateral root development. This produces a denser, more extensive root system, which in turn improves nutrient and water uptake from the growing medium. For cuttings and seedlings, this effect is particularly valuable. A cutting that establishes roots quickly has a head start that compounds throughout the grow. Growers regularly report faster rooting times and more uniform root development when Azos is applied at the propagation stage.
Stress resistance
Azospirillum bacteria also produce compounds that help plants cope with environmental stress — including drought stress, transplant shock, and temperature fluctuations. Plants treated with Azos tend to recover more quickly when conditions are less than ideal.
How to Use Azos
Azos is a powder product, straightforward to apply at several stages of the growing cycle.
For cuttings and seedlings
Mix 4 tablespoons (approximately 60ml) of Azos per gallon (4.5 litres) of water to create a solution. Soak your grow plugs or Rockwool cubes in this solution for 10 minutes before use. Before inserting a fresh cutting, dip the cut tip into a paste of 1 part Azos powder to 2 parts water for 15 seconds. This direct inoculation at the cutting site gives the bacteria immediate access to the developing root zone.
For transplanting
When transplanting seedlings or rooted cuttings into their final growing medium, dust the root ball lightly with dry Azos powder, or water in with an Azos solution at the point of transplant. This minimises transplant shock and supports rapid root re-establishment in the new medium.
As an ongoing supplement
Azos can be incorporated into your regular feeding schedule throughout the vegetative stage. Add it to your watering solution at approximately 2 tablespoons per gallon of water. The bacteria continue to colonise the root zone and fix nitrogen as long as conditions remain favourable — adequate moisture and temperatures between 15–30°C.
How quickly does it work?
The bacteria in Azos begin working within 20–60 minutes of application. Visible effects — faster root development in cuttings, stronger early vegetative growth — are typically apparent within the first 1–2 weeks of use.
Is Azos Compatible With My Growing Setup?
Azos is compatible with most growing systems and media:
- Soil: works particularly well in organic growing media, where the bacterial populations integrate naturally with the existing soil ecosystem
- Coco coir: highly effective — the bacteria colonise readily in well-aerated coco/perlite mixes
- Rockwool and inert media: best applied at the propagation stage via a solution soak
- Hydroponic systems: Azos can be used in hydroponic setups, but bacteria populations in a recirculating system may be less stable than in substrate growing. Best used during propagation and early establishment phases.
Azos works well alongside other Xtreme Gardening products — particularly Mykos, their mycorrhizal inoculant. Azos supports nitrogen fixation and early root stimulation; Mykos extends root reach and improves phosphorus uptake. Together they address two of the most important root-zone biological processes simultaneously.
Is Azos Safe?
Yes. Azospirillum brasilense is a naturally occurring soil bacterium found in agricultural soils around the world. It is not harmful to humans, animals, or the broader soil ecosystem. Azos contains no synthetic chemicals, is registered for use in organic growing systems, and carries no hazard classifications under standard UK/EU labelling. It can be used safely alongside most nutrient lines and supplements, though it’s best to avoid applying Azos at the same time as products containing high concentrations of hydrogen peroxide, as these will kill the bacteria.
Azos vs Synthetic Nitrogen Fertilisers
Azos is not a replacement for your main feeding programme — it’s a biological complement to it. Conventional nitrogen fertilisers supply nitrogen immediately in a readily available form; Azos supports a sustained, natural nitrogen input through bacterial fixation. The two approaches work well together.
The practical advantage of Azos over relying entirely on synthetic nitrogen is in the root zone: you can maintain healthy nitrogen levels for your plants while reducing the overall mineral salt load in the growing medium. This lowers the risk of salt accumulation, reduces the frequency of flushing needed, and contributes to a more balanced root environment over the growing cycle.
Frequently Asked Questions
Azos has a shelf life of approximately two years from the date of manufacture when stored in a cool, dry place away from direct sunlight. Keep the lid firmly closed between uses to prevent moisture ingress, which can reduce bacterial viability over time.
Azos is compatible with most mineral and organic nutrient lines. Avoid applying it simultaneously with strong oxidising agents or products with very high copper or zinc concentrations, as these can be bactericidal. As a general rule, apply Azos in plain pH-adjusted water rather than mixing it directly into your full nutrient solution.
Azospirillum bacteria are most active between 15°C and 30°C. Below 10°C, bacterial activity slows considerably. In UK growing conditions, this is rarely an issue in an indoor growing environment with adequate heating, but worth being aware of if using Azos in a cold greenhouse or outbuilding in winter.
Yes — the two products are designed to be used together and address complementary aspects of root biology. Apply both at transplant and during the establishment phase for maximum effect. Mykos mycorrhizal fungi extend root reach and improve phosphorus uptake; Azos bacteria fix nitrogen and stimulate lateral root development. They don’t compete with each other.
Azos is available in several sizes to suit different growing scales — from smaller 2oz trial sizes through to larger 12oz and 6lb containers for commercial growers. For most home growers, a 2oz or 6oz container will last one to two full growing cycles used as directed.
Further Reading From The Horticulture Company
For more expert growing guides, our nutrients and additives guide explains how to build an effective feed programme, while our LED grow lights comparison and grow tents guide help you optimise your growing environment. The indoor growing environment guide covers temperature, humidity and CO₂, and the complete UK grow tent guide takes you through setup from scratch.
For authoritative guidance on plant nutrition and health, the Royal Horticultural Society publishes evidence-based growing advice used by professionals and hobbyists alike. Visit The Horticulture Company’s store in Kenilworth, Warwickshire, or browse our full range of products and guides online.
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