We recommend starting relatively warm in the vegetative stage with room temperatures of about 26°C or 80°F to maximise growth rate. Then reduce the temperature from late vegetative to early flowering stage to 20°C or 68°F. This reduces the bud temperatures to preserve terpenes and cannabinoids such as THC before harvest.
Temperature Control for Early Vegetative Growth
The vegetative stage is critical for establishing a strong, healthy plant structure that can support prolific flowering. During this stage, medicinal herbs benefit from a warmer temperature that supports fast growth. This pushes the plant to expand the canopy to fill the grow space and maximise the absorption of light.
Maintaining temperatures between 25-28°C (77-82°F) during the vegetative stage promotes vigorous growth. Warmer temperatures accelerate metabolic processes, including photosynthesis and nutrient uptake, leading to faster growth rates and stronger plants.
Temperature control for the early flowering stage
Reducing temperature as the plants progress into the flowering phase helps the plant generate and retain cannabinoids. Lowering night time temperatures to 15-20°C (59-68°F) while keeping daytime temperatures between 20-24°C (68-75°F) stimulates the plant to increase resin production and reduces losses through evaporation.
The flowering stage is where medicinal herbs focus energy on producing buds rich in cannabinoids like THC. It is best to reduce temperature to stimulate the plant to concentrate terpenes and cannabinoids in the flowers or buds as they are forming.
The bud temperature will be higher than the room temperature by up to 5°C or 10°F. High bud temperatures will stress the plant and cannabinoids and terpenes will evaporate.
If you are using HPS grow lights the grow room temperature should be lower
The bud temperature will be much higher than the room temperature under HPS lights because they emit a lot of radiated heat to the plant canopy. Bud temperatures will be lower relative to the room temperature with LED grow lights which barely emit any radiated heat.
How to control temperature in the grow room
Here are key strategies to achieve this:
- Run your lights at night time: The temperature is lower at night and even with lights and other equipment running the grow room should be cooler at night.
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Advanced Climate Control Systems: Utilize automated climate control systems that can regulate temperature, humidity, and CO2 levels with high precision. These systems should be capable of making real-time adjustments based on sensor feedback to maintain optimal conditions.
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Ventilation and Airflow Management: Proper ventilation is crucial for maintaining temperature and preventing mold and mildew. Use fans, exhaust systems, and air circulation equipment to manage airflow and distribute heat evenly throughout the growing area.
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Thermal Imaging Cameras: Regularly use thermal imaging cameras to monitor the canopy temperature of the plants. This technology helps in identifying areas that might be overheating or under-heating, allowing for timely adjustments.
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Data Logging and Analysis: Keep detailed records of temperature data and plant performance metrics. Analyzing this data helps in understanding how different temperature regimes affect growth and THC production, enabling fine-tuning of the crop steering strategy
Conclusion
Temperature-controlled crop steering presents a powerful method for enhancing the growth rate of medicinal herbs during the vegetative stage and increasing THC content during flowering.
