In this article we will talk about the optimal conditions for your growing set up, to get the best growth and maximum yield. Plants of course need adequate water and nutrients to grow healthy, but photosynthesis which is the driver of the plant growth, will be largely determined by the amount of light the plant receives, the amount of CO2, and the temperature of the environment which will determine the rate that the photosynthesis occurs. The data and the references that we're using in this guide are taken from a university study published in 2008 by scientists Suman Chandra, which are laboratory studies carried out on a high potency strain of cannabis sativa. They looked at the influence of different temperatures, light intensity, levels in PAR and CO2 levels and the effect on plant growth.

 So let's look at each of these in turn.

So first we look at the level of light intensity that the plant is receiving. When we're talking about photosynthesis, we discuss light in terms of the horticultural reference which is PAR (Photosynthetically Active Radiation). At PAR levels up to 1500 µmol/m²s you get increased growth rates however it's also shown that once you pass 800 µmol/m²s, the rate of growth that you get is not really worth the amount of extra light energy that you input into the plant. Therefore it is generally accepted that around 800 µmol/m²s is the best tradeoff between getting maximum growth and not having to use too much energy. In the vegetation stage you would aim to get about 50% of those levels, approximately 400 µmol/m²s. You can achieve this by getting your light fixture reducing the output by using a dimmer or by just raising it about 1.5 to 2 times higher than its optimal hanging height.

the optimal temperature for plant growth was tested at two different light levels. Medium PAR intensity level of 500 µmol/m²s and a very high level of 1000 µmol/m²s. In both instances the maximum plant growth rate occurred at 30 degrees Celsius. Of course different strains have different requirements, but in terms of temperature our suggestion would be that a safe band of temperature to operate in would be between 25 and 32 degrees Celsius.

Finally we look at the impact of different levels of CO2 on plant growth. Normal atmospheric level of CO2 is about 370 parts per million. If you are introducing air circulation with fan (and carbon filter), it is highly likely that you're maintaining that atmospheric level of CO2 in your grow room. It is very hard to increase the CO2 level because if you introduce more CO2 into the grow area, it will only get drawn out just as quickly by the fan. It is therefore almost impossible to artificially raise CO2 levels.

But there are a couple of ways of doing it! You can enclose the environment, so that the air recirculates back into the grow room or is recirculated around the grow room. Combining the use of a CO2 sensor and some form of adding CO2 by CO2 bags or CO2 burners, can artificially elevate the CO2 level in your grow room.

Another method you could use is to use effectively natural and free sources. We all expel CO2 when we're breathing and therefore in occupied buildings the CO2 level is often raised as much as twice the level in comparison with the external atmosphere. If you can take air into your grow room from an occupied building or workplace you will most likely increase levels of CO2 into your grow room and increase the growth rate.