Most organic cannabis growers will understand the importance of having as strong a root system as possible in order to grow high yielding crops.
Growers add mycorrhizal fungi to their soil, for example, to significantly increase the efficiency of their plant’s root systems. These special fungi help the plant to absorb nutrients more efficiently and the results are a far healthier and more robust plant.
But affecting the roots of cannabis plant can do more. Much more. About 200% more, in fact.
Root Zone Temperature Optimization
An Israeli-based company State called ‘Roots Sustainable’ have discovered some very important effects of heating the roots of their cannabis plants. They are calling it Root Zone Temperature Optimization or
The idea is that the plant’s roots are heated up or cooled down in order to keep a steady temperature and protect the plant from any external temperature variations.
In recent tests using 81 heated plants and 82 unheated cannabis plants, figures indicated an increase in the final dry weight of bud of between 60% and 283%.
Not only was the final weight up significantly but the overall weight of leaves was also much larger. The plants are obviously thriving under the


These differences are very significant and have far reaching consequences for the commercial growing industry – and perhaps even smaller growers growing their own personal crops.
Obviously, larger yields mean more profit – encouraging news indeed for commercial cannabis cultivators throughout the world.
The notable increases in dry weight were not strain dependent either; it happened across a variety of different cannabis strains, so it would seem to be a universal effect that works on all cannabis plants.
How does RTZO work?
The system works by using water pumped through pipes to heat or cool roots by a variance of up to 10 degrees celsius.
Thanks to the design of the system, using heat from the earth and exchanging it to maintain steady temperatures, the whole system can run solely on just one pump. This means the system runs on very little energy and is very cheap to run.

On their website, Roots Sustainable explain their technology as follows:
“The RZTO system is based on the phenomenon that, at a depth of a few meters, soil maintains a relatively stable temperature that approximates the mean annual air temperature and is unaffected by daily or seasonal air temperature fluctuations. The underground temperature is always colder during the summer and hotter during the winter than the top soil temperature.
“Leveraging the principle of Ground Source Heat Exchange (GSHE), Roots installs a closed-loop system of pipes, where the lower part is installed at the stable temperature depth, and the upper part in the target crop’s root zone.
“Water flowing through the lower pipes is charged by the soil’s stable temperature. The heated (or cooled) water is pumped through the pipes installed in the root zone, where the heat (or cold) is discharged.
“The system is able to heat the root zone during the winter and cool it during the summer (by up to 10° Celsius), maintaining the RZT at a relatively stable and
What root temperature is best for cannabis?
Roots Sustainable say “the optimal day temperature range for cannabis is 15°to 30°C (59 to 86 °F). Temperatures above 31 °C (88 °F) and below 15.5 °C (60 °F) decrease THC potency and slow growth.At 13 °C (55 °F), the plant undergoes a mild shock.
“Young cannabis plants in the vegetative stage prefer temperatures slightly warmer than in the flowering stage, in the 70-85°F (20-30°C) range

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“Significant opportunities”
The CEO of Roots Sustainable Dr Sharon Devir claims that the results reflect the efficiency of their climate management systems. She said:
“The global cannabis market offers significant opportunities for our root zone heating and cooling technology, with promising results in both greenhouse and open field environments.
The highly competitive US cannabis market is increasingly adopting agtech solutions, which lower initial capital outlays while maximising crop production, quality and profit year-round.”
These figures would suggest that commercial growers using their root climate control system could generate an extra US$150,000 (£116,000) to US$300,000 (£232,000) per 30,000 square feet each growing season.
However, this revelation is sure to raise the eyebrows of anyone who grows cannabis for any reason.