What growing environment is best for my lighting system?

By Lee G Lyzit     1 February 2019 


Question: I'm about to grow Tangerine Dream from seed. I have a 2x4x6-foot tent with 1,200W full spectrum LEDs. What should the air temperature and humidity be, and how far should my LEDs be in each stage? Thanks for helping this noob.

Answer: Thank you for your question. When growing in a small enclosed area (like a grow tent), atmospheric conditions are a major concern. Since you are growing from seed, you will need to know the atmospheric conditions for each stage of cannabis growth.

To begin, you will need to have your atmospheric conditions conducive to the seeding stage of growth. Typically, seedlings prefer a higher humidity (65-75 percent) and a temperature range of 75-80°F. Instead of trying to maintain a high humidity level in the entire grow tent, you may want to use a humidity dome with a seedling tray. Your LED light will work for this stage, but it should be placed far away from the seedlings, as it may be too intense for young seedlings. The grow lights should be on for 18 to 24 hours a day. Many growers opt to use a small fluorescent lamp for this stage of growth.

Once the seedlings have produced a few sets of true leaves (the leaves that look like actual cannabis leaves), they are ready to be treated as vegetative plants. The atmospheric conditions for the vegetative stage are similar to the seedling stage. The humidity range should be 55-65 percent and the temperature should be kept between 70-75°F (assuming you are not supplementing CO2, which would require a slightly higher operating temperature). At this stage, the artificial light source can be placed closer to the canopy as long as it is not causing any burning (bleached/white looking growth at the very top). If your LED lighting system allows you to tailor spectrums, this is the stage where a blue spectrum would be more applicable. The photoperiod, or “lights on,” should be set for 18 to 24 hours.

Finally, once you are ready to initiate the flowering period (by reducing the photoperiod to 12 hours per day), you will need to watch the atmospheric conditions more closely. If possible, the humidity during the flowering stage should be kept below 55 percent. Higher humidity in the flowering stage can lead to pathogenic molds and rots. The temperature in the flowering stage should stay in the 70-75°F range (again, assuming you are not supplementing CO2). It is also important to make sure the “lights off” temperature does not vary more than 10 degrees from the “lights on” temperature. A large temperature swing from “night” to “day” can cause spikes in humidity. In this stage, your LEDs should be hung as close to the plant canopy as possible (without causing damage to the plants). Light radiation diminishes exponentially, so the closer you can have the lighting system to the plants, the more usable light energy is available for photosynthesis. If your LED lighting system allows you to tailor spectrums, this is the stage where a red spectrum would be more applicable.

Original post: https://www.maximumyield.com/what-growing-environment-is-best-for-my-lighting-system/7/17499