Despite being one of the factors least considered by less experienced growers, maintaining and in this case, lowering the indoor temperature is one of the most important tasks. Especially in summer, heat becomes an implacable enemy of our plants, being able to significantly reduce the production of buds, or even lead our loved ones to death. And we are not exaggerating.
There are different methods to keep heat at acceptable, even optimal, levels. Some are more sophisticated than others, varying in cost and effectiveness.
But before approaching the different techniques, we first go to the theoretical aspects.
What is the correct temperature?
While it may change slightly between different strains, the optimal temperature for a crop tends to be the same for almost any marijuana crop. But beware, it changes depending on the growth stage in which our plant is.
table indicating the optimum temperature according to the cycle of the marijuana plant
When heat is a problem, you should focus on avoiding spikes in temperature, rather than achieving the ideal temperature. Even for a short time, a sharp rise in Celsius can be very damaging and even fatal.
It should be noted that there is a close relationship between temperature and humidity. The higher the humidity, our plants can tolerate temperatures better. Both aspects must be cared for and controlled.
It depends on the stage in which our plant is
Seedling: When our little ones are starting to grow, the temperature during the cycle of light on should be between 20 and 25 C. With the light off, the ideal is that our habitat does not drop below 15 C.
Humidity should be high, around 65-75% relative humidity. Our little ones do not have functional roots yet, and must absorb moisture from the air.
Growth: Our plants are now ready to have more activity. The temperature rises slightly, where the ideal is to keep it between 22-28 C. in light cycle, and 18-22 C in darkness.
Relative humidity can start from 70% and gradually decrease between 5 and 10% weekly, but not less than 35%.
Flowering: Here we need our plants to breathe a lot, in an environment similar to autumn. The temperature should be 20-26 C. in light cycle and 16-22 C. in darkness.
Humidity should be around 45% without exceeding 60%, as high humidity increases the chances of suffering fungal attacks on the buds.
Techniques to lower the indoor temperature
We have a wide range of techniques to use in order to lower the temperature of our indoor. Some require buying grow items, but others are completely free and / or homemade.
Reverse cycle: The simplest and completely free. It consists of fitting the hours when the lighting of our indoor is on with the low temperatures outside time -night, obviously- and the hours with the highest external heat keeping the lighting off. That is, by day, the lighting off, at night, on.
LEC or LED lighting: These types of indoor lighting emit less heat than HM / HPS. They are more expensive equipment, but with less electricity consumption and less heat generation. For more information check our post: Led vs Sodium Lighting.
Remove the ballast from the growing place: On the other hand, if we have HM / HPS lighting, we can remove the ballast and keep it outside the cabinet. This avoids a heat source inside the crop.
Intractors and extractors: The extractor is a fundamental part of our indoor kit, which draws out the hot air already used by the plant. It also generates passive intraction, which is the air that enters the closet through its windows due to the internal vacuum produced by the extraction. However, many times it is not enough, and we must complement with an intractor, in charge of entering fresh air with greater forceinto the interior of the crop.
Intractors and extractors outside: If we have ducts available, the ideal is to keep both intractors and extractors working outside the cabinet, as these also generate a heat share.
Remove the hot air from the room: On the other hand, if possible, ensure that the air extracted from the indoor is directed directly outside through a duct.
Ventilated room: Regardless of whether or not you can take the air from the indoor to the outside, it is always desirable that the room in which the crop is located is well ventilated. Not only because of the temperature, but also because of the accumulation of oxygen and the lack of CO2. Creating or promoting a constant air flow, even a slight one, is a great contribution.
Ventilated reflectors: There are certain types of closed reflectors designed to be connected to the extractor through a duct. In this way it is possible to directly extract the heat generated by the bulb to the outside, without going through the habitat of the plants. An example of this type of reflectors is the Garden Highpro Maxlight Coolbox or the Cooltube. This solution reduces various degrees of heat in our farm.
Ice: In case of an emergency, some growers put ice in the interaction mouth of the indoor kit, such as bottles with frozen water. With this you can achieve a basic and somewhat tedious reduction, but achievable in any house, and it can be effective in smaller grow rooms.
Air humidifier: This component is recommended to always have in an indoor crop as it is especially effective in combating heat. Although the temperature does not drop much, the humidity in the air allows plants to better withstand heat. It also allows us to control humidity at any time, improving the quality and productivity of our plants. Here is recommended humidifier from home.
Air conditioning: If you have tried everything in the fight against heat, and you have a good budget, a final solution is the use of air conditioning. This allows us to directly lower the temperature, either indoors or in the entire room where the crop is located. It has a high electrical consumption, and its cost is high, but it represents a definitive solution to the problem
Watering with cold water: Finally something that seems simple and obvious, but has caused more than one problem for several growers. If the tap water comes out warm or hot, or if you water with bottles that were in the sun, you better wait for them to cool down. Warm or hot water can strongly affect the roots, which we know are very sensitive. Always water with ice cold water (not close to being frozen either), fresh, and hopefully it has rested a day or two to discard part of the chlorine.