Light During The Dark Cycle

by David
(northern CA)

My partner isn't sure how important the the dark part of the day actually is. I say it's absolutely important that not even a pin hole of light get in. We're trying to figure how we can use a CO2 generator during the dark period because of the pilot light.

Answer: David- For plants that require a dark period to flower, the dark cycle is extremely important....and those plants are very sensitive to changes in the dark period from one day to the next. This advice is not only a word of caution, but also the answer to your problem.

You would think, because from time to time there is a full moon outside, that these plants could not possibly be sooo sensitive to a little bit of light during their dark period. But for some reason, plants grown indoors from start to finish seem to be notoriously sensitive. Perhaps, when grown outdoors, the plants simply adapt to the 30 day lunar cycle- after all, it IS pretty darn regular from cycle to cycle. Or, perhaps, the plants can sense the extra gravitational pull of the moon and therefore have learned to ignore the extra light from the shine of the moon during these periods. Who is to say? (not me, lol)

But one thing is for certain....indoor plants freak out over any small difference from one night to the next, so perhaps a regularity IS the key after all. Obviously, there is no way in hell you are ever going to duplicate the complicated pattern and regularity of a lunar cycle (and I can't think of any real benefit to doing so). However, you CAN focus and making things very regular from one night to the next.

In this way of thinking, you will have a regular cycle....a 24 hour cycle. The light must come on at the same time each day. The light must go off at the same time each night. And the amount of light INSIDE the grow room during the dark period must be exactly the same from one night to the next, with NO interruptions.

Many people who do not completely understand the finer processes at work here simply beat the drum that the grow room needs to be completely, absolutely dark. I surely used to be one of those people. And the reason it works it not necessarily because it is completely dark in the room- it works because it is exactly the same night after night after night.

I have been gardening indoors now for 15 years. Even though I have begun to understand some of the finer points of plant psychology during that time, I was aghast when I went to visit a friend the other day and his flowering room during the dark period had so much light in it that you could see everything in the room quite clearly and easily.

Even though I was aware of exactly the same thing I am telling you, I was also very concerned for the health and well-being of his plants. But there they were....solid, growing normally, with not one single hermaphordite flower on any of the plants. Furthermore, he had been carrying on like that for over a year without a problem.

That experience solidified my understanding, and also leads me to my advice to you. Go ahead and wait until your current crop is done flowering before you make any changes. After that, go ahead and install that CO2 generator in your flowering area and never give it a second thought. That tiny amount of light will make no difference at all, especially if it is exactly the same night after night after night starting with day 1 of your next flowering cycle. I hope this helps David, and Happy Growing!