Why Do Weed Plants Need Darkness?
If you have spent any time in marijuana forums or talked to a somewhat experienced grower, you have been told that the dark cycle is very important for your plants. When I first started, one of the first things I remember being told was how important it is to provide marijuana plants with complete darkness. Meaning no seeping light or peaking in on the plants when they are sleeping! Having ‘peaked’ my interest, I thought I should investigate this further.
Why do weed plants need darkness? Complete darkness triggers the flowering and growth of buds on marijuana plants. When in darkness, weed plants are respiring and require a porous soil/substrate. In darkness, marijuana stops photosynthesising and producing oxygen. Stored energy produces more carbohydrates in darkness, which allows the plants to grow (Calvin cycle).
If you want a more detailed explanation of the Calvin cycle, there is a link at the bottom of this article. Suffice it to say, having dark time for your plants is beneficial. A lot of growth happens when the lights are off. It is important to have your set-up done in a specific way to allow maximum growth to happen. In this article, I will go over why it’s important to have darkness, how much darkness and other things you can do to grow the biggest and healthiest weed plants possible. Let’s begin!
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 Time of Day Should Grow Lights be Off?
I recommend turning your grow lights off at a time that you won’t want to peak into your grow tent. A time when you are most likely to be sleeping is the perfect time, in my opinion.
The first time I grew in an enclosed area, I made the mistake of having the lights off in the early evening which is when I wanted to do most of my plant care. This didn’t work as I quickly realized I couldn’t be letting lighting into the grow area. I ended up doing my plant maintenance early in the morning before I went to work.
How Dark Does the Flowering Room Need to Be?
When the lights are out, the plants should be in as dark a room as possible. Having too much leaking light can cause a plant to go hermaphrodite or flipping into the flowering stage and back to veg.
This is very stressful for your plants and will either ruin your yield completely or at minimum slow down the time it takes for your plants to be ready for harvest.
How Much Light Will Stop Marijuana from Flowering?
I have heard that 14 hours is the magic number. Personally, I wouldn’t recommend any more than 12 hours of light. If my plants were receiving more than 12 hours, I would start worrying that they would be knocked out of the flowering growth stage.
Do Buds Grow the Most During Darkness?
A lot of growth does happen when the lights are out. Sometimes however, when I watch my plants during the daytime, I can almost see them growing.
I think technically, buds do grow more during the night, they lengthen and thicken very nicely. In the daytime, they appear to lengthen more than they thicken. This is probably just my imagination.
After reading that confusing information, I can honestly say that yes, I believe the buds grow more during darkness than when the lights are on.
24-Hour Dark Period Before Harvest
It’s believed that turning the grow lights off for up to 24 hours or more before you harvest will bring out purples and other colors in the buds before cutting them down. As well, the potency is supposed to increase, and it will be a smoother plant to smoke.
I am only reporting what I have been told or read over the years on this one. I haven’t done this yet but will on my next grow. The one thing I question however, is how do you know this for sure, unless you have 2 identical plants and harvest one immediately and the other only after a period of darkness. Then, when cured, smoke them and see what you think.
Even still, a plant could just have more potency than another regardless of the little bit of darkness before you cut it down.
I am not trying to discourage you from trying this for yourself, I am just asking the question how would you really know? Regardless, I will be trying this, if in fact it smoothens the smoke out a bit. After all, I am all for it!
Thanks for reading and good luck on your next grow.
Reference:
Related Growing Marijuana World Articles
Best Reasons to Use a Grow Tent for Weed
Different Ways to Heat a Grow Tent
How Much Area Does a 1000 Watt Grow Light Cover?
