To what extent should you play around with lighting cycles whilst growing marijuana? If looking to produce quality cannabis in an indoor grow space, should you be experimenting with lighting cycles? Or is it simply a case of following experts’ instructions to the letter?

For many cannabis growers, half the fun lies in experimentation. They get a real kick out of writing their own rulebook, predominantly making things up as they go along. Unfortunately, this is only a viable system if you don’t mind staring failure in the face, more often than not. Particularly when it comes to things like cannabis lighting cycles, there are standards that should be adhered to.

Marijuana Plant Photosensitivity

When getting into cannabis cultivation for the first time, it’s important to build an understanding of photosensitivity. Cannabis is a photosensitive plant, which means that the lighting patterns it is exposed to can and will trigger set responses. Marijuana plants need a certain amount of light and darkness during each 24-hour period, in accordance with the strain, its life cycle stage and so on.

In its native environment, nature provides everything marijuana needs to grow strong and healthy. Cannabis plants go through an extensive vegetative stage, during which they soak up as much light as possible. This enables them to build a strong and robust physical structure, focusing all their energy on growth and development. But when the seasons change and the days become shorter, longer nights trigger the cannabis flower production process. The plant knows that this is the time to begin focusing on the production of flowers, ending the vegetative stage and commencing blooming.

The beauty of growing indoors being the ability to take full control of lighting cycles, from the moment you plant your cannabis seeds. For the experienced grower, meticulously timing the production of cannabis flowers to suit their priorities is a common tactic.

Vegetative Cycle: 24 Hours or 18 Hours?

During the vegetative stage, indoor growers typically swear by one of two very different lighting cycles. For some, there’s no better solution than providing vegetative cannabis plants with 24/7 continuous lighting. They believe that by stimulating the plant to continue photosynthesizing around the clock, they’re guaranteed larger and stronger plants as a result.

At the opposite end of the scale, others advise limiting provision of light to 18 hours per day. Their argument being that this is a much more accurate replication of natural outdoor growing conditions. There’s also the theory that plants can benefit from photosynthesis breaks, rather than expecting them to perform 24/7.

As usual, evidence paints a somewhat contradictory picture. While some growers report significantly faster growth with 24/7 light, others warn of stunted growth, nutrient deficiencies and other serious issues. Sticking with 18 hours of light is considered the safest way to go, but there’s room for experimentation with a little more.

Flowering Cycle: 12-Hour Lighting

When focus shifts to flowering, marijuana plants require a good 12 hours of darkness per day. These longer nights and shorter days trigger the release of hormones within the plant, which in turn lead to the production of flowers.  Perhaps even forcing the production of more blue and purple flowers. Once again however, there’s much debate as to the most effective lighting cycle to use during this stage.

Some claim to have achieved outstanding results by varying light and darkness provision during the flowering cycle. 12 hours of darkness followed by six hours of lighting, 12 hours of darkness followed by 9 hours of lighting and so on. Nevertheless, there is no specific evidence to suggest that these alternative light cycles have a positive impact on the final harvest.

Instead therefore, most advise sticking with the usual 12/12 split. 12 hours of darkness, followed by 12 hours of light and so on. Or if you prefer, do whatever you can to recreate the exact lighting conditions your chosen cannabis strains would be exposed to outdoors.






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