Lighting Hours

Hi Scott

What do you recommend as the best lighting hours in the growth vegetative stage? I’ve been told that with an electronic timer you can run 18 hours on and 12 off but is this optimal or 18/6 optimal? I’m a little confused because I’ve been told 18/12 gives you an extra day of light in every four days but do plants need this much light because if they do in theory 24 hours always on would be best in the vegetative stage. On another note the same person told me when the plants begin to flower to turn the lights off and give them complete darkness for two days (what?) and this really brings incredible results for the flowering stage. Please let me know as your opinion is always valued?

Critical to know that plants count dark hours, not light hours. Avoid this person, if that’s the advice you are getting. Sounds like my mate said, or my experience shows…. The problem with one persons experience is that it shows inconsistencies or abnormalities as facts and rules.

Plants deprived of light will tend to stretch, and this impresses some growers. By reducing nutrient strength a plant might grow 5 inches a day, but the yields are down. People that advise hundreds of growers over years, learn all the things that work or don’t work.

A short day plant is triggered to flower when its chlorophyll has been deprived of light for 12 hours. If you increase or decrease daylight length, this does not affect the flowering.

12 hours of light (not even a crack of light) gives fast flowering/fruiting/harvests changing the night to 14 hours will not generally affect it, but the longer you wait before giving more light, the more time the plant is hungry. 2 days of darkness will reduce the effectiveness of phyto-hormones and enzymatic activity in the plant, and could reduce the yield as well as cause the plant to stretch. 2 days of light in a lighting cycle might give the plant more energy to perform well. So this would be beneficial.

The main thing people are getting confused is the day length is irrelevant, but the night length is. If you run the lights say, Monday night, and Tuesday off, Tuesday night on, wed am off, and use the manual “on” setting on the timer to override the occasional off cycle to stop them going to “night” the plants will not notice. They cannot distinguish between a 12hour day, or a 36 hour day. 36 hours is common because it means the timing is the same on a 24 hour timer, it just goes around 24 hours and another 12 hours to the normal off time.

Some research has shown that plants do not benefit with over 15 hours of light, and experience with our growers shows otherwise. Light is energy, the more the better, but the off cycle triggers oxygen respiration, waste production through the roots such as ethylene, phyto-hormonal activity. Ever seen plants grow over night. Its more common than not.

Anyhow that should answer your Question