Temperature for cultivating cannabis

To develop well, your cannabis bushes need appropriate temperature in the room. The plant likes warmth, and the air in the room where you plan to cultivate the plant should not be too dry or wet. In the daytime, the temperature range should be from 20°C to 30°C. At night, the air in the room should be cooler.

Why does temperature matter for growing marijuana?

Now I’d like to share with you what problems you may face in case of improper temperature regime in the room where you plan to grow marijuana. What will happen to the plant if the room temperature is too low? In cold temperatures, hemp bushes slow their growth. For example, in a room with a temperature of 15°C, hemp bushes will stop growing and developing. Lower temperatures can kill the plant. Some hemp varieties can grow and develop in the cold, but you won’t get a big harvest of fragrant and saturated cones.

Bushes are very susceptible to certain types of mold that appear after hypothermia and frost. In the daytime after the night coolness, the icy water appeared on the plant begins to melt, spreads throughout the bush, leading to the appearance of harmful mold. Moreover, a very low temperature leads to excessive leaf bending and reduced photosynthesis.

Plants growing in a very hot room also slow their growth. For example, a temperature exceeding 26°C adversely affects the growth of buds at the flowering stage, they can become airy and loose. Furthermore, the heat leads to decreased scent and richness of the bud taste. In a very warm room, the bushes may suffer from red spiders, white powdery mildew, root rot and other problems.

In the premises where you plan to grow cannabis, I strongly recommend installing:

  • dehumidifier and heater when needed, these devices can raise the temperature while lowering the humidity;
  • instead, you can use an air conditioner, it can easily lower the temperature and humidity;
  • cooling evaporator – this device lowers the temperature and increases humidity;
  • the humidifier can increase the temperature and humidity.

With these devices, you can easily create the optimal climatic conditions for growing marijuana bushes.

What does the temperature in the room affect?

Well, let’s go on and see what else the temperature affects in the room where you intend to grow marijuana.

First, the temperature affects the color of the buds and leaves. Temperature is capable of suppressing or revealing blue, magenta and pink colors, provided that the cultivated strain is genetically predisposed to this.

Secondly, the temperature affects the growth of your bushes. If high temperatures prevail in the room at night, this will slow the growth of your bushes. Therefore, at night reduce the temperature to 18°C-20°C, this will help stimulate the growth of your plants.

Third, temperature affects the humidity in the room. If the air in the room is very humid, then dew or a water film will appear on the leaves of your bushes, which will lead to mold and rotting of the buds. In a room with high humidity, bushes will slow their growth. You can solve this problem by setting an optimal temperature regime. Moreover, the temperature and humidity indicators are interconnected – you can solve the problem with one indicator by adjusting the other.

Throughout the entire cultivation process, regularly monitor the temperature and relative humidity – only in this case you can get the best harvest. Remember:

  •     too hot and dry air will slow the plant growth;
  •     too cold and humid air will slow the growth of bushes, and mold or fungus may appear on their leaves.

Fourth, the proper temperature is the key to a successful drying and curing process. It defines how long you can store the harvest.

By setting the desired temperature regime, you can independently adjust and control the growth of bushes. By increasing the temperature in the room at night, you will slow the growth of bushes which have become too high or are growing too fast. This technique is suitable, if the room where the cannabis bushes are growing has too low ceilings.

The optimal temperature at different stages of life

At different stages of development, marijuana bushes need different temperature indicators. Now, I will say more about each stage of plant development and the temperature they need.

Temperature needed for hemp at the seedling stage

At the first stage or the stage of seedlings, the room temperature should be 20°C to 30°C, humidity within 70%-80%. During this period, the plant should receive water through leaf transpiration until the root system is finally formed.

Therefore, at this stage, many growers use special domes that can increase humidity. However, make sure that the humidity does not exceed 80%, otherwise harmful mold or fungus can appear on the plant.

      Temperature needed for the vegetative stage

At this stage, the most comfortable temperature for the plant is considered to be 20°C to 30°C. Young bushes are growing and developing more quickly at an average or high humidity in the room, which should be about 40%-60%. At night, the temperature should be lower, this will promote faster and healthier vegetative growth of marijuana bushes.

Temperature needed for the flowering stage

At this stage, the most comfortable temperature for bushes is considered to be from 18°C to 26°C. Keep this temperature regime throughout the entire flowering stage. In this case, the humidity in the room should be medium or low – 40%-50%. At night, the temperature should be slightly lower than in the daytime. By keeping a lower temperature, you will help the plant produce more powerful, dense, fragrant cones rich in trichome. If the temperature in the room is kept above 26°C, then the growth of the buds slows, and the terpenes will simply evaporate.

Speak plainly, high temperature will make the buds too dry at the flowering stage, which will affect their taste, scent and psychotropic qualities. It is very important at the end of the flowering stage to keep a cold temperature at night. However, do not overdo it, because your bushes should not freeze, the cold can make the cones hollow and loose. If the cannabis variety you planted has a gene for producing colored buds, keep low temperatures at night 2 weeks before the end of the flowering stage. Thus, the plant cones will show color: purple, pink, blue, etc.

Temperature of drying cannabis

Why is it so important to properly dry the harvested cones? Because this will affect their quality, taste, and scent. Therefore, it is very important to keep an optimal temperature and humidity during drying and treating the cones. If you do everything properly, you may rest easily about harvest safety, it will not be exposed to mold or over-drying. After harvesting, the buds should be dried indoors at 21°C and a relative humidity of 50%. Then place the cones in a glass jar and continue drying at the same temperature, with a humidity of 58%-65%.

How should I control the temperature in the room?

There are various ways to control the room temperature, but I recommend the following:

Use a temperature control monitor. This device will show not only the temperature, but also the relative humidity. I prefer using multiple temperature control monitors from different manufacturers. Thus, I can determine the temperature indicators more exactly in the room where marijuana bushes are growing.

Adjust too high or too low temperatures. Today, there are different devices to control and, if necessary, adjust the temperature in the room for growing cannabis. The most suitable device is a universal heater and air conditioner.

Depending on the room size, use either a portable or wall-mounted air conditioner.

If the room is too hot, make sure that the ventilation system is working properly. Ensure constant air circulation in the room, because it affects the growth of your bushes. Therefore, the room should be equipped with fans for proper air circulation. Also, a variable or evaporative cooler can lower the temperature in the room.

If the room is too cold, you can insulate it with a special insulation film that will help to retain heat, or simply buy an additional heater. Naturally, it is easier and cheaper to isolate not the entire room, but only the boxes where the bushes are growing. Also, you can purchase a tent to mark the outer boundaries of the cultivation zone.

Alternative power source. Every beginner grower should be prepared for a situation when the power may go out. You need to have at least one (or several) of the proposed devices:

  1.   Inverter. These devices are powered by a car cigarette lighter. The inverter is an excellent backup power source, but to use it, you need a car, which is not always possible. These devices can be used if you cultivate marijuana bushes in a garage or the garage basement.
  2.   Uninterruptible power supply. UPS is not capable of working for a long time or holding a large charge. Most often, such devices are used to protect electrical equipment and computers. If you are not going to spend much money to purchase a large charger, then UPS is what you need.
  3.   Gas generator. This is another one backup power source, which is often used in case of power outages. Each grower living and growing marijuana in areas with often power outages must have such a device.

What is needed to keep the optimal temperature?

Lighting devices used in the room for growing cannabis warm up and dry the air. To avoid this effect, follow the basic rules and monitor the balanced operation of all systems. But first things first.

Lamps. The temperature in the middle of the grow box largely depends on the lamps. Most hemp growers use HPS lamps. However, these lamps overheat the air. Special ventilated lamps will help get rid of this. Also, you can use energy-saving and LED lamps, which are not strongly heated.

Throughout the entire growth cycle, I advise you to carefully monitor the bushes; after have noticed any signs of illness, immediately take measures to eliminate them:

  1.   The leaves darkened, curled up and began to fall off little by little. It can be caused by too low temperature. You can solve the problem by using an additional heater.
  2. The leave tips dry out, and the lower leaves completely fall off. Inflorescences began to die without blooming. These changes in the plant may report signals on too high temperature. Ventilation and air supply will help solve the problem.
  3. Leaves on the bushes began to grow yellow, lose their tonus and colour. These symptoms indicate sudden changes in temperature. To solve this problem, arrange a special temperature control in the dark and daytime. In this case, you can benefit from temperature sensors.

Ventilation. The ventilation system will help to keep the ideal temperature inside the box. The air conditioner will discharge heated air and provide fresh air from the outside. Using the ventilation system, you can lower the temperature inside your grow box by 5 degrees or more. If a usual ventilation system fails to meet the requirements to cooling, you can use a ventilation system with an additional cooling effect.

In an emergency, you can quickly lower the temperature inside the box by supplying fresh air.  However, in this case, note that when you open the doors frequently, you significantly reduce the illumination. If your grow box is on the porch or in the garage, you cannot do without additional heaters. Also, additional fans will help to lower the temperature in the box.

Humidifiers. You can also lower the temperature inside the box by 2-3 degrees using an air humidifier. The humidified air has a beneficial effect on the bushes, since the lamps not only warm the air, but also dry it out. However, do not become so engrossed with humidifying the air, but adhere to the following recommendations:

  •     the allowed humidity for seedlings should be 80%-95%;
  •     to stimulate the growth of high-quality greenery, the air humidity should be in the range of 65%-70%;
  • at the flowering stage, 60%-65%.

If the air humidity at high temperatures is high, it will lead to bacterial and fungal diseases, which adversely affect the bushes. Use a hygrometer to determine the humidity level in the grow box. Therefore, I advise you to buy this device.

Devices for automatic temperature control. To facilitate the microclimate control process, you can use some innovative devices for automatic temperature adjustment. This kind of devices has built-in user-programmable sensors, and if necessary they can enable or disable the ventilation system.

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