Article Written by: Luis Rivera
If you are new to growing medical or recreational marijuana there is a risk you may not know enough about it’s light cycles and photosensitivity. The amount of light and dark within 24 hours leads to different responses within the plant. To master the speciality of growing cannabis and cater to the plants’ needs, a new indoor grower must learn the differences between the flowering and vegetative cycles.
Vegetative stage
The vegetative stage is of great importance for the life of your cannabis plant. It is also known as the growing stage of the plant. The cannabis stems and leaves grow bigger and taller. During this stage the plant does not produce buds. What you would need to do as a grower is to control the size and shape of your plants during the vegetative stage. When the conditions are proper, the plants tend to grow very fast during this stage.
Cannabis will stay in the vegetative stage as long as the plant gets short nights (less than 11-12 hours of darkness each day). For the plant to stay in this stage, you must make sure it gets at least 13 hours of light. Otherwise, it might start budding before you’d like.
Thirteen hours of lighting is the bare minimum. The plant can receive as much as 24 hours of light, or at least 18 hours of light a day. These two options are known as the 18-6 and 24-0 light schedules, and encourage faster vegetative growth. The eighteen hour light duration is closer to the natural light of summer. This schedule is preferred by some growers during the vegetative stage, who argue that plants benefit from rest from a biological point of view. Although plants grow faster under the 24-hour light duration, they might develop some nutrient deficiencies.
Outdoor growers must know that as long as the plants are getting plenty of light per day, they will stay in the vegetative stage from late spring until late summer.
Many gardeners don’t realize that the problems they are experiencing in the blooming stage are 
occurring because the plants didn’t receive a proper dark cycle in the vegetative stage. During the vegetative stage, the time spent in darkness enables marijuana plants to translocate nutrients, meaning to translocate energy stored in the form of sugars and prepare itself for another day of vigorous growth. This is why it is recommended to have an 18 hour lights on and a 6 hour lights off cycle for the vegetative stage.
Some problems that you may experience in the flowering stage of your plants are a result of the plants not receiving a proper dark cycle in the vegetative stage. During this stage, the dark cycle enables cannabis plants to translocate energy stored in the form of sugars, as well as to translocate nutrients. That is why, some growers prefer the 18-6 schedule, instead of 24-0.
Flowering stage
The hormones of the medical marijuana plant depend on the amount of darkness it receives. Most marijuana strains require at least 12 hours of darkness to trigger the hormones responsible for the flowering process. Usually, the marijuana strains need at least 12 hours of darkness for the hormones, responsible for the flowering process, to be triggered. To put it in a simpler way, your plants need a minimum of 12 hours of darkness to start creating flowers.
If you are an outdoor grower, you will notice that outdoor plants start budding in late summer when days are longer. For indoor growing plants, the light schedule should be estimated at 12-12 hours, as 
mentioned above. What it means is that the indoor grower will need to induce flowering by artificially changing the light schedule to 12 hours of light in a day, and 12 hours of constant darkness. Once the lighting schedule is changed, there is an average of 2.5 months before the plant’s buds will be ready for harvest.
It is important to remember – experimenting with the light cycles and not following some gardening tips entirely is okay! Many great techniques that are now commonly used came from experimenting growers. However, if you are a newbie in the growing sphere (especially the indoor one), sticking to certain rules and techniques is recommended. What you need to remember is that marijuana needs at least 12 hours of darkness during the flowering stage, and (preferably) an amount of dark periods during the vegetative stage.
About the Author: Luis has 20+ years of experience in global market expansion, business development, mergers and acquisitions, business re-engineering, finance and investor relations of software companies. He is passionate about technology, spectral science, indoor farming, food production, automation, and more. Since 2015 he is the president of Advanced LED Lights, a leading LED grow lights manufacturer based in Hiwasse, Arkansas. When not at work, Luis enjoys swimming, yoga, as well as growing grapes and flowers in Sonoma, California.
