Why Is Darkness Important for Indoor Plants?

 Light is a massive part of growing cannabis. When you think of a cannabis grow, you probably picture a room with huge, brilliant lights shimmering above a crop of plants. But nature loves equilibrium, and as such, cannabis loves darkness too.

In the dark, cannabis plants go through different processes than they do in the day. The length of the dark cycle tells them what time of year it is, triggering different stages in their development. Cannabis seeds cannot germinate without darkness indicating they’re beneath the soil, and darkness protects the roots of cannabis from unwanted infestations and disease.

So, to neglect the dark cycle in your cannabis grow is to neglect the plants themselves. With a bit of care, it is easy to achieve the total darkness that plants need to properly flourish. By the time harvest comes around, you’ll be grateful you made the effort.

The Importance of Darkness for Weed Plants

Probably one of the most important aspects of providing darkness to weed plants is the fact that when you shorten the amount of lighting, the plants are receiving is what encourages the marijuana to switch into the flowering stage. At the end of your grow, it’s big buds that you want on the plants.

In the daytime under the sun or grow lights, your plants are continuously converting light into energy and when the lights go out that energy is what causes your plants to grow. Another way to explain it is the plant takes the light’s energy and converts it into a chemical energy (or sugars) in the plant.

This chemical energy is what causes the plant to grow. Even though growth happens 24 hours a day, you can expect that more growth will happen when the lights are turned off and the plants are then utilizing that light energy from the day.

The overall health of your weed plants depends on how much dark time you provide them. I am not sure if this is valid anymore (or not) in the world of cloning and growing generations of plants indoors, but every marijuana plant has a natural light cycle it will grow best too. I mean, if a plant is native to a region at the equator, then a 12/12 light cycle for the flower stage just seems natural.

If you have seeds for plants that are native to a more northern region, then the darkness could potentially be longer. This all depends on where the seeds originate in the world. Whether that is valid or not anymore in the world of indoor growers, that’s up for you to decide and discover.

How Much Darkness is Important for a Successful Marijuana Harvest?

Now we know darkness is where a lot of growing magic happens for your weed plants. If you gave too much darkness though, I am not sure it would help. Here is why.

Providing more than 12 hours of darkness means your plants will be in the light absorbing energy for shorter periods of time even though the plants need the dark they also need the light just as much. Your weed plants need that light energy for photosynthesis to occur.

Having said that, if you have a plant you want to take clones (a mother plant) from, you will want to keep it in the vegetative stage. If this is the case, then never go lower than 14 hours of light per day. This should keep your plants from flipping into the flowering stage (until you want them to).

What Happens To Plants At Night?

Cannabis plants have two key light spectrum receptors: phytochrome red and phytochrome far-red. When the sun is shining or the grow lamps are switched on, the levels are balanced. However, during the dark cycle, far-red receptors change into red. With a long enough dark period, the balance eventually tips to mostly phytochrome red. Then, photoperiod cannabis is triggered to commence flowering. They are biologically programmed to do so.

This is why outdoors during long spring days, photoperiod strains are in vegetative growth and won’t flower until late summer/autumn when the nights get longer. Most photoperiod cannabis grown outdoors will transition to bloom gradually — usually when the sunlight is reduced to 13–14 hours per day.

Indoor growers run an 18–6, 20–4, or 24–0 light cycle to prevent too much phytochrome red from building up and inducing bloom too soon. In fact, photoperiod cannabis can remain in the vegetative stage indefinitely, if long days can be maintained that is.

On the flip side, many growers will leave plants in complete darkness for a day or two before switching to 12–12 to accelerate the transition to bloom. This is achieved via the phytochrome red buildup during the prolonged period of darkness.

The Consequences Of Interruptions To The Dark Cycle

You can’t afford interruptions to the dark cycle. Light leaking into the grow show during the dark cycle will stress your plants without a doubt. If you must observe your cannabis at night or when the lights go off, green light is the only option. Even autos won’t perform as well if the dark cycle is disturbed. Sure, they can cope better, but they are not invincible.

External light sources hitting cannabis plants during the dark cycle could prevent them from blooming, and in the worst cases, shock them into turning hermie. Moonlight is not a threat, but that’s really the only exception. Even using your mobile phone as a torch could be enough to destroy the dark cycle and do damage. Keep the dark cycle completely dark.

Conclusion

Darkness helps marijuana plants replenish THC and terpenes. During the day, THC partly degrades and terpenes partly evaporate. So the best time for harvest is early morning. And if you extend the night before the harvest to at least 2 days, you can (arguably) get more flavorful and potent buds. We’re sure many of you have already tried this method. Did it work for you? Please share! In the end, the darkness is important, but if you need a grow light to grow plants, recommend you ECO Farm LED grow light.