Temperature and humidity are critical environmental factors that significantly influence plant growth and development in controlled indoor cultivation systems. Along with factors such as airflow, light, and water, they play a pivotal role in determining the overall health and productivity of the plants.
To effectively control temperature in an indoor growing environment, several methods can be employed:
- Heating Systems: If the ambient temperature is too low, growers can utilize various heating systems such as forced-air furnaces, hydronic radiant heating, or electric resistance heaters to raise the temperature to the desired range.
- Cooling Systems: When the temperature exceeds the optimal range, cooling systems like air conditioners, evaporative coolers, or chillers can be used to lower the temperature and maintain it within the desired parameters.
- Ventilation and Air Exchange: Proper ventilation and air exchange systems can help regulate temperature by introducing fresh air from the outside or expelling hot air from the growing area, depending on the temperature differential.
- Insulation: Proper insulation of the growing area can help maintain consistent temperatures by minimizing heat loss or gain through the walls, floors, and ceilings.
- Dehumidification and Humidification: Temperature and humidity are closely related, and controlling one often affects the other. Dehumidifiers can be used to reduce excess humidity, which can also lower the perceived temperature, while humidifiers can increase humidity levels if needed.
Regarding the specific temperature range mentioned, cannabis plants generally thrive in a temperature range of 68°F to 77°F (20°C to 25°C) during the vegetative growth stage and slightly lower temperatures around 68°F (20°C) during the flowering stage. However, it’s essential to note that these temperature ranges can vary slightly depending on factors such as strain genetics, growth stage, and other environmental conditions.
To maintain optimal plant health and maximize yields, it is crucial to carefully monitor and control temperature and humidity levels within the recommended ranges for the specific cannabis cultivars being grown. This often requires the integration of multiple temperature and humidity control systems, along with precise monitoring and adjustment based on real-time environmental data and plant responses.
Now let’s explore how to control the temperature in a grow tent together!
The ideal temperature for cannabis
- Seedling stage: 68-77°F
- Vegetation stage: 71-82°F
- Flowering stage: 68-79°F
- 1-2 weeks before harvest: 68-79°F
Note: Cannabis-like fluctuations of 10°F between day and night (when your lights are on versus off).
How to increase the temperature?
If you are growing your plants during winter you’ll need to keep your tent warmer, especially at night since the natural temperature will drop dramatically.
Low temperatures can cause a number of problems. Seed germination requires temperatures between 65—75°F—obviously, it will be easier to germinate during spring or summer, but this sometimes isn’t possible. Low temperatures stunt germination, but it also stunts growth throughout the life of cannabis: at temperatures below 65°F the plant will slow its growth, and at temperatures below 59°F. your plant will stop growing altogether.
Once a cannabis plant has been affected, it will take about 2-3 weeks for it to return to a normal growth cycle. Naturally, you don’t want this to happen. It will not only waste your time but also reduce your yields overall.
Here are some ideas for controlling the temperature in your tent:
An electric heater
An electric heater is a common option among growers. They can heat up your tent even in the coldest winter. However, there is one point you need to keep in mind, heated air is dry, so don’t let hot air directly blow into your plants. Choose an electric heater specifically designed for tents, one equipped with a thermostat so they can turn the heating on/off according to the changes in temperature.
Heat mats
Heat mats are mainly used for germination since seeds sprout when the soil temperature reaches about 70°F. This doesn’t mean you have to remove the heat mats after germination. Actually, many growers continue to use heat mats beyond the germination and seedling stages—with some, you can wrap the heat mat around a pot to keep a plant’s roots warm.
This helps plants because in cold weather water and minerals can condense in the soil and when this happens it becomes more difficult for your plants to absorb water and nutrients from the soil. Heat mats can be used to warm the soil even after germination.
Lighting period
Usually, we turn on the light in the morning and turn it off in the evening, matching our own schedule. However, you can interchange the lighting period—try running the lights at night to counteract the cold of the night in winter. Grow lights are a great heat source (of course, this depends on the type of lamp—HID lamps produce more heat while LEDs produce less).
The insulation
Another solution you could look into is using some insulating fabric or material that can help isolate your grow tent from the external environment. There are a lot of cheap options online that can help retain heat in your tent—this can help reduce your electric bill when you combine it with a space heater.
How to decrease the temperature?
In contrast, temperatures that are too high can also be harmful to your plants and will cause them to wilt or die over time. Here are some tips on how to control high temperatures:
Air conditioners control temperature in a grow tent
While an electric heater can be used to warm grow tents, we can also use an air conditioner to reduce heat. Like when you use a heater, an air conditioner dries out the air so make sure you balance humidity with a humidifier or by adding wet towels or other sources of moisture into the tent.
Ventilation system
To cool the tent, you need to ensure there is a proper air exchange from your tent, removing the hot air and bringing in the cool air. If you want to decrease the temperature, you can increase your fan speed or invest in a second fan. Air change can not only cool your tent but also help plants to develop stronger stems and leaves.
CO2
The increase in Carbon dioxide levels can’t decrease the temperature, but it can help cannabis to endure higher temperatures.
Grow lights
HPS and high-power grow lights produce more heat than LED grow lights. If you are constantly dealing with high temperatures while using HID bulbs, try changing your grow lights to LED grow lights which can keep the LED grow lights away from your plants.
Also, try keeping your lights on at night and turn them off during the day since during summer months the temperature is already high during the day, and running the lights produces excess heat, which is not good for your plants. When the temperature drops at night you’ll have a lower temperature range for your lights to play with.
As long as you grow indoors you’ll have to keep track of the temperature so we highly recommend investing in a thermometer (a hygrometer is also needed to measure humidity). Thermometers are not expensive and will save you money over time and keeping track of environmental changes can help you offset problems before they arise. Prevention is always better than cure!
There are a ton of ways to control the temperature in your tent, and the subject is probably one of the most fun and interesting parts of growing. We’ve even seen some people turn our tents into Swedish saunas, which is wild. (Although this isn’t something we can recommend!)
We’re happy to help you on your growing journey, and while our advice is just a starting point, we hope it gives you some ideas going forward. Do you have any tips to control the temperature in your tent? Let us know in the comments! We’d love to add some ideas to the article.
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