When growing plants indoors, the goal is to replicate the natural environment as closely as possible. To simulate the different seasons, from long daylight hours to shorter ones, it’s crucial to maintain temperature and humidity levels that match the plants’ needs.
In this article, we explore the importance of keeping the right temperature and humidity levels throughout the various stages of a plant’s life cycle, how to control the indoor environment, and potential risks to be aware of when growing indoors.
What is the Optimal Temperature for Indoor Plants?
This varies greatly from one plant to another, so it is best to consult the ideal conditions for your plant and your variety and adjust as much as possible to them.
In general, and especially generative plants, tend to prefer warmer environments. It is best to aim for a temperature between 20 and 24 degrees. It is important that the temperature remains stable whether the lights are on or off. You can even play around with lowering the temperature a couple of degrees when the lights are off to mimic the natural day/night cycle that plants experience outdoors.
What is the Optimal Humidity Level for Indoor Plants?
The ideal humidity level varies depending on the plant’s type and its stage of growth. Usually, during the early stages, such as seedling and vegetative phases, plants prefer warmer and more humid conditions, with a relative humidity of around 50–80%. As plants mature, particularly during the flowering and ripening stages, it’s best to lower the humidity to about 50%, aiming for 35–50% during peak production. This is the best way to avoid problems with fungi, and to prevent them from ruining your crop just before harvesting.
How to Control the Temperature When Growing Indoors
Not every indoor growing space will naturally meet the ideal conditions. Here are some methods to help control the temperature and humidity levels in your growing environment:
Extraction:
An extractor helps remove large volumes of air from the grow room, exhausting it away. The efficiency of your extraction system plays a significant role in maintaining the ideal temperature ranges.
Electric Heater:
During the colder months, adding a heater to your grow room can help balance the ambient temperatures, keeping the room within the correct range. Heaters are particularly useful at night when the lights are off and there’s no external heat source.
Temperature Fan Controllers:
These devices can be connected to fans, heaters, and extractors, using sensors to automatically maintain the desired temperature in the grow room without needing constant supervision. Though they can be an investment, they save time and ensure a stable environment.
How to Control Humidity Levels When Growing Indoors
After covering temperature control, let’s discuss how to manage humidity. Below are different methods to regulate humidity levels indoors:
Humidifiers:
Humidifiers can transform a dry room into a more suitable environment, creating a wet, foggy atmosphere ideal for plants during their vegetative stage. They come in various sizes, making them suitable for both small and large grow spaces.
Dehumidifiers:
If humidity levels get too high, especially during wet seasons, a dehumidifier can remove excess moisture from the grow room. This is particularly important during the flowering stage, as high humidity can negatively impact the plants.
Always Use a Hygrometer:
To accurately monitor temperature and humidity levels, use a digital hygrometer. These affordable devices provide real-time readings and often track the lowest and highest readings over a 24-hour period.
The Potential Risks of High Temperatures and Humidity Indoors
• Risk of Mold: High humidity levels during the late stages of growth can lead to mold development.
• Heat Stress: Elevated temperatures can cause heat stress, leading to various issues, including stunted growth and poor plant health.
• Increased Pest Activity: Pests, including insects and mites, thrive in warm, humid environments.
• Reduced Quality: High temperatures can negatively affect the quality of the yield, resulting in less vibrant and lighter flowers or fruits.
What is Heat Stress, and How Do I Identify It?
Heat stress is caused by rising temperatures in your grow room, which can quickly become problematic. Identifying symptoms early can prevent further issues. Below are some common causes and signs of heat stress:
• Hot Grow Lights and Ballasts:
Grow lights, especially during extended periods, can generate a lot of heat. This is particularly challenging during the vegetative stage when lights are on for long hours.
• Hot Weather Outside:
During summer, unexpected heatwaves can cause indoor temperatures to soar. Running your grow lights at night can help mitigate this issue.
• Poor Ventilation and Extraction:
Old or inadequate ventilation systems can lead to a buildup of heat and humidity. Upgrading your extraction system every few harvests is a good practice.
• No Oscillating Fan:
Oscillating fans help circulate air around the plants, preventing hot spots. Without these fans, your grow room can quickly become too warm.
What to Look Out for When Identifying Heat-Stressed Plants
1. Leaves Curling Inwards:
Plants respond to hot, dry conditions by curling their leaves inward to reduce the amount of surface area exposed to light and minimize water loss.
2. Small and Stunted Plants:
Exposure to high temperatures can stunt growth, leading to poor health and smaller plants. This means less productive and inferior quality harvests.
3. Low Yields:
Some plants are very sensitive to high temperatures, and flowering is affected by them. Flowering may stop and the flowers may not set, or the plant may not flower at all.
If the plant, despite the adverse conditions, manages to flower, high temperatures drastically reduce the yield and quality of the crop.
Conclusion
Maintaining the right temperature and humidity levels throughout your plants’ life cycle is key to successful indoor cultivation. Investing in the right tools—such as a digital hygrometer, humidifier, dehumidifier, oscillating fans, and an electric heater—will help you create a stable and controlled environment. Consistency is essential; keeping your plants happy and stress-free will lead to the best results.
