A common question I get asked is when you are growing in a grow tent, where should you put the thermometer to get an accurate reading?
It is a valid question to ask, because depending on the size of the tent and the type of lighting you are using readings could vary drastically from the top to the bottom of the tent. Things get even more complicated if you are using a thermo hygrometer and want accurate readings of humidity levels as well. You are right to do your research and make sure you are getting accurate readings, as temperature and humidity levels can often be the cause of a list of problems for your plants. This article will address the question of where to place your thermometer, and educate you on typical symptoms your plants exhibit when there is trouble brewing with temperature or humidity levels.
There are a few solutions to the question of where to put your thermometer in your grow tent. The quick and simple answer? Everywhere. But how can temperature vary so much in such a small space? It really does depend on what you are growing, how much of it you’re growing per square meter, the type of lighting you’re using and the quality of ventilation and airflow you have. All of these factors play a part in your grow environment, and all of them can change temperature levels significantly. Let me explain.
For instance, if you are using an HID light in your grow tent, this type of lighting emits a large amount of heat. Left unattended this heat would sit at the top of the tent, and slowly creep down to your plants the longer it says on. Installing a proper inline fan and ventilation system helps to dispel this stale hot air, but it does not mean heat is not being generated and emitted regularly by the light. Placing a thermometer too close to this light will throw off temperature readings as it would likely be much hotter an inch from the light than it would be at the bottom of the tent. Alternatively, placing your thermometer at the bottom of the tent will not necessarily give an accurate reading of temperature near the plant canopy.
So how to solve this conundrum? Solution 1 is to simply purchase 2-3 cheap thermometers or thermo hygrometers and place them at height specific intervals throughout the tent to get an idea of temperature and humidity at the plants roots, base, and canopy. Another more temporary solution is to rotate where you place the thermometer in the tent on a daily or bi-daily basis. This should give you a fairly accurate reading so long as external factors around the tent are not affecting readings too much. This means that outside or household humidity and temperature levels are not fluctuating by too much when moving the thermometer to the next location.
If you choose to rotate your thermometers location, or even if you took the safe route and purchased several thermometers, be sure to keep a look out for temperature and humidity related symptoms with your plants. When growing cannabis a typical sign of under temperate conditions is when plant leaves begin to darken significantly and even turn purple in colour. Conditions that are too cold and you will be lucky if the plant survives the night. If it is too hot on the other hand, and your plants leaves will begin to fold in half.
While an environment that is too hot will not directly lead to plant death, it does weaken the plant and delay growth, which opens the door to other problems such as pests, mold or the leaves being burnt. Other symptoms that are a bit more general, but could be related to temperature include leaf edges looking burnt or turning brown, curling leaf edges, wilting or drooping leaves, or the entire plant looks to be wilting or drooping.
So it’s therefore important to regularly check the temperature and humidity of your grow space. Having a few strategically placed thermo hygrometers will help to identify any issues with your grow environment and help you address them before they become an issue for your plant. Now you’re ready to take on your grow environment with this added knowledge. Get what equipment you need, and start growing! Check out my equipment recommendations page, or click here to see what the best value equipment on the market is and where to find it.
'Prof' is a professionally trained Canadian teacher with a love of horticulture and advocate of the democratization of cannabis cultivation, especially for medicinal purposes.