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Cannabis Light Cycle Schedule for Indoor Weed Growers

Modern technologies and approaches have massively improved how we grow cannabis for commercial use, allowing us to grow stronger and healthier plants in a fraction of the time. Part of this improvement comes from an increased understanding of how conditions such as lighting should be adjusted across the various stages of cannabis growth.

Providing you understand the basics of how a cannabis plant grows, and how to adapt your conditions to the various weed plant stages, it’s easy for you to take advantage of all of this knowledge to substantially boost the performance of your commercial cannabis business.

The Growing Stages of the Weed Plant

Weed plants pass through several distinct stages of growth before they’re ready to be harvested, taking them all the way from dormant seeds to flowering plants ready to harvest. Gaining a basic understanding of these stages is the first step to being able to optimize your growing process.

Since the plants will gradually transition from one stage to the next, some growers will divide them slightly differently from others, but the principles and methods which work will remain the same regardless.

Germination Stage

Germination Stage cannabisThis is the start of your plant’s journey, and is the time in which it first breaks out of the seed and shows signs of life. During this time the seeds are sensitive to changes in conditions such as temperature so it’s advisable to keep things as consistent for them as possible. After a period of three to ten days, you should see your plant start to emerge as a seedling.

Seedling Stage

marijuana seedlingYour plant will slowly develop during this stage, and will gradually start showing the trademark signs that it is a cannabis plant, in particular the distinctive, fan-shaped leaves. This stage usually lasts between two to three weeks and ends as the plant enters the vegetative state.

Vegetative Stage

marijuana Vegetative StageThe plant is typically considered to have entered the vegetative stage once it has between six and eight sets of pointed leaves. At this point, it will have a well-developed root network and is ready for a period of significant growth as it continues to grow and gain more leaves. This stage can last anywhere between 3 and 16 weeks, and you can exert control over this through your light management.

Flowering Stage

marijuana Flowering StageThis is the stage where your plant begins to develop buds, which later emerge as flowers. This stage can be divided into three parts. During the initial phase, any female plants will develop pistils, which look like white hairs and are the beginnings of buds. In the mid-flowering phase, other growth will stop as these pistils fatten out into proper buds. Towards the end of the flowering phase, the plant will become very sticky and the buds will change color as it becomes time to harvest. All in all, the flowering stage typically lasts 8 to 12 weeks.

Cannabis Light Cycle Schedule

cannabis grow room set up with lighting, irrigation, and fans

Understanding these growth stages allows you to plan your cannabis light schedule in a way that keeps your plant healthy while it moves through them as quickly as possible. This is important because your plants will have different lighting requirements in different stages of growth, and your cannabis light schedule can even be what triggers the plants to move from one stage to the next.

Germination Stage Lighting

The seeds and the roots don’t require any light, meaning that there are no lighting requirements during the germination stage. However, you should ensure that there is sufficient moisture for your seeds to germinate and that the temperature is kept constant during this time. If you’re germinating your seeds before planting them in the soil, it is recommended to keep them in relative darkness to imitate natural conditions.

Seedling Stage Lighting

This is where you can begin to use your cannabis light schedule to optimize the growth of your plants. During the seedling stage, you’ll want to provide your plants with around 18 hours of light per day, whilst gradually increasing the lighting intensity as the plant prepares to enter the high-growth vegetative stage.

Vegetative Stage Lighting

During the vegetative stage, you should continue to provide your weed plants with 18 hours of light per day in order to support all the growth which occurs during this part of the plant’s lifecycle and to prevent the plant from entering into the flowering stage too early. The plant can remain in this stage of its lifecycle indefinitely providing the light cycle isn’t changed, with the flowering process being induced by a reduction in lighting hours to 12 once the plants are fully developed.

Flowering Stage Lighting

Your weed plants will begin to enter the flowering stage once you reduce the lighting to just 12 hours per day. Although they may see some rapid growth and other significant changes during this time, it isn’t strictly necessary to adjust the lighting cycle, but a small increase to 13 or 14 hours per day during the mid-flowering stage can help to maximize bud growth. This can be reverted to 12 hours per day and light intensity reduced during the late flowering period.

Frequently Asked Questions

How Much Light is Needed for Weed Seedlings?

A lighting cycle of 18 hours on, 6 hours off is tried and tested for weed seedlings, so most growers will be best off sticking with this tried and tested method. Some growers do experience success with longer lighting hours per day, but this is not a common recommendation and will likely also increase energy costs.

It is important to be aware of the light’s intensity during this time as well, which should be gradually increased as the weed plant advances toward the vegetative stage of its lifecycle.

Best Light Cycle for Vegetative Stage

Things are even simpler during the vegetative stage, with a light cycle of 18 hours on, 6 hours off being almost universally recommended at this point in the plant’s life. A reduction in light will result in the plant moving into the flowering stage and developing pistils, which grow into buds. Care should be taken that this isn’t triggered too early, but once the plants are ready, you should move to 12 hours on, 12 hours off light cycle to allow this to happen.

Whilst it may seem like there is a lot to consider, you shouldn’t have any issues providing you take your plants’ growth one stage at a time and plan your light cycle carefully based on these proven recommendations. If you want to make things even simpler and get your growing business off to the best start, contact us to find out how one of our custom grow box solutions can ensure that you have everything you need for your plants to prosper while getting as much as possible from your available space.

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