Cannabis Light Cycles for Commercial Indoor Growers



The LED lights are the supplemental source of light that help cannabis plants grow vegetatively and fulfill their lighting requirements for the complete lifecycle indoors. LEDs are typically designed to help plants stimulate seedlings’ growth, trigger vegetative development, and take them to maturity, provided the other factors remain ideal. LED lights initiate photosynthesis in plants that are incapable to receive direct sunlight, or the foliage of plants can’t perceive an ample amount of light to complete the redox reaction that converts it into usable chemical energy. Such conditions exist when growing indoors in greenhouses or hydroponic arrangements. Different plants need a variable light cycle from the seedling stage to maturity, and only the quality LED lights can complement this need through all growing stages. Although the hobbyist dominated the Cannabis growing culture during the initial years of cultivation, commercial indoor growers are now speedily adopting this practice due to the high revenue-generating crop. Commercial indoor cannabis growers typically rely on broad-spectrum lights that yield between 385 nm to 780 nm to control the process of Photomorphogenesis, where every light spectrum controls several growth parameters together. The cannabis plant remains hungry for light throughout the growing cycle, and only the quality LED lights can supplement through all growth stages. The lights which allow controlling intensity, wavelengths, temperature, and distances from the foliage of the Cannabis plants during the entire growth stages could prove more yielding than the ordinary lights.

Importance of Light Cycles for Successful Cannabis Crop Indoors

The light is the most important constituent that impacts the quality and quantity of Cannabis, especially when grown indoors. The intensity and the duration of the light energy which we also term a light cycle, determine the conversion of CO2 into useable energy that contribute towards the growth of Cannabis besides developing roots. Primarily, the light cycles observe two roles in the growth and development of Cannabis. Firstly, the light cycles act as the catalysts in cannabis that mobilize it from the vegetative to flowering stages. Secondly, light cycles also enhance the biomass of cannabis which otherwise is directly proportional to an increased yield, a greater number of flowers, and more growth cycles in a calendar year. An efficient light cycle seamlessly induces a strong daily light integral (DLI) which means a greater number of photons per square meter per day. Since Marijuana is a short-day crop, the indoor commercial growers can take the lead from the extended or the reduced light cycles to grow earlier or delay their crop whatever suits them. Cannabis needs variable daily light integrals through all growth stages which becomes easy to adjust when the growers know the exact DLI values for different growth stages.

Relation Between Cannabis Light Cycles and Daily Light Integral (DLI)

 Since understanding the Cannabis Light cycles and their relation with DLI are the most critical parameters for a successful commercial crop indoors, it becomes pertinent to know how it behaves when the desired DLI is not achieved. But it could adversely affect energy costs, prolong harvest time, and reduces Cannabis yield drastically. Otherwise, adjusting these light cycles offers indoor Cannabis growers the ability to choose the desired DLI during different stages of Cannabis growth. During seed germination, the process may require DLI ranging between 10 to 12 mol per square meter per day which can be achieved with hours of light cycles provided the LED source possesses full wavelength. The light cycle for the seedling stages increases to 18 hours or more since the DLI requirement increases between 12 to 16 mol per square meter per day for the Cannabis crop. Early vegetative stages demand an increase in DLI from 25 mol and onwards, for which the light cycle is adjusted to 18 hours to give the desired indentation. The DLI demand for the late vegetative stages could rise to 55 mol per square meter per day and be achieved with 18 hours of light cycle in Cannabis. Inducing flowering in Cannabis requires 12/12 light cycles with a redder light to meet the DLI above 60 mol per square meter per day. However, the ideal mean average for the DLI remains 65 mol per square meter per day. However, some Cannabis strains may mature earlier or later with a minor difference in the light cycles, and often the breeder of any strain could better guide the light cycle and nutrient requirements of each. The selection of the right light spectrum, light cycle, wavelength, and DLI contribute to the changes in the THC levels, Terpene, and Cannabinoids in Cannabis.

Cannabis Light Cycles

Cannabis Growth Cycles

Typically, a Marijuana growing light is broad-spectrum and holds variable wavelengths to meet its growing cycles. After the Cannabis seeds germinate, they pass through different physiological growth stages. i.e., seedlings, early vegetative, late vegetative, flowering, and bud formation.

Germination Cycle

The light cycles for all the stages are different as far as the wavelength of LED Lights is concerned. On average, the Cannabis seeds need 7 days to complete the germination process. No doubt the Cannabis seeds remain in the dark during this period, but they need a splendid amount of light and heat for proper germination. Typically, 16 hours of the light cycle remains ideal for germination. Otherwise, the 14/10 light cycle can be chosen as a standard.

Seedling Cycle

The indoor Marijuana seedling cycle completes in about 21 days, and the seedlings may need to develop 5 to 7 leaflets during this period. As the number of leaflets exceeds, the Cannabis light cycles are also enhanced. Most commercial Cannabis growers expose seedlings to 18 hours of light followed by 6 hours of darkness.

Early & Late Vegetative Cycles

After 21 days the Cannabis plant enters an early vegetative stage and needs a bluer spectrum for robust growth. The light cycle for vegetative growth differs in both early and late vegetative stages. This stage continues for another 3-weeks when the Cannabis plant needs a moderate amount of watering and nutrients. Excessive fertilization could hamper growth. However, once the Cannabis plant moves to the late vegetative stage, it needs more nutrients and irrigation. Normally, the late vegetative stages continue from the 7th week and could continue up to the 14th week. However, depending on the Cannabis cultivars, these stages could fall as earlier as 3 weeks But, not later than the 16th week. The ideal lighting cycle is again 18 hours of light followed by 6 hours of darkness. Anyhow, the light cycles for the last 2 to 3 weeks during the late vegetative stages can be adjusted to 16 hours of light and 8 hours of darkness which can induce rapid flowering.

Flowering & Bud Formation Cycles

The marijuana flowering stage is the most critical and sensitive of all growth stages that determine the success of any commercial grower and brings fruit to their efforts. Cannabis plants demand redder than other wavelengths and can be exposed to a stronger red for 12 hours. The practice increases the THC level in Cannabis which most commercial growers want from their crop. In these cases, the day and light cycles reach 12/12 for many Cannabis strains.

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