Mine are 12 hour and I might increase that to 14 in the summer, but that is about it. Plants need to have time for darkness functions...follow nature. What happens there, we should do the same.

No, from what I've been told this is a myth.

I keep my lights on 14 hours in summer, 12 hours in spring and fall, and 10 hours in winter. They all bloom and grow well this way and ''know'' their schedules.

Careful studies in non-orchid plants show that it is the total photon flux that a plant receives that is important. There is a maximum amount of light a plant can use and anything beyond that is not a positive. So, an under lights grower would lengthen the light exposure to make up for a reduction in illumination, if that is happening. We can't go by foot candles/lumens measurements exclusively because it depends on the wavelength distribution of the lights.

With my LED lighting situation, known wavelengths of the light, and measured foot candles I am using 17 hour days for most of the year to equal what would happen in a well positioned greenhouse in my Northern area that limits maximum illumination to 1,500 foot candles with the use of shading.

Do you leave the lights on 7 days a week, or do you leave them off one or more days a week? I have my timers set for 10 hours winter and slowly ramp them up to 16 hours summer. But I was wondering if running them everyday puts stress on the orchids. In the wild there are rainy and cloudy days after all. Any opinions?

Mine come on at 5 am and go off at 9 pm

I have a slight variation on what everyone has already reported....it is cheaper to run my lights after 7pm. So since I grow in the basement with no sunlight, mine come on at 9pm and run for 11 hours for winter. I will slowly adjust the time near spring to be longer and turn on later as the seasonal electric rates change. No idea how much money it saves but because the boiler that heats our house is in the basement too, it is running a lot during the coldest part of the day which is night, so the basement enjoys a warm up when the lights come on. Coincidence and I don't know if the plants care but it seems more natural for them.


Ryan

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Contrary to what you've been told, Orchid Boy, that is NOT a myth. There is nothing in the man made world of lights that can compare to the sun. Yes, the sunlight varies at times of the day and seasonal and blockage by weather and clouds and trees BUT it's still the BEST light ever. Between the consistency and lengthening the duration of our lighting it comes as close as we can get to real sunlight. Without either of those it's like comparing a bucket of water to a lake !

Mine are on a timer 12hrs/day, 7 days/week and 15 hrs/day during daylight savings.

I found this website to be a great source to find out how long to keep the lights on during different times of the year. It goes by which latitude you live on.


Day Length

Yes, orchids from equatorial regions get 12 hours of daylight - but bear in mind that's not all full daylight. There is dawn, sunrise, dusk, and sunset in nature, when the light is not as strong and comes from a lower angle. Artificial lighting sources typically blast their light down on the plants with no variation in strength for the whole time they're on. Under bulbs, the total light the plants receive is far more than they'd get in nature. Thus, I like to go down to 10 or 11 hours in winter, up to 14 or so in summer. -Stephen

I would only add that it all depends on the intensity of the light that you can deliver with artificial lighting. The weaker your intensity, or the more suboptimal your light spectrum, the longer your day length needs to be to compensate. Obviously, this applies to a greater degree to higher light requiring orchids. There are published data on the illumination at a spot throughout the day, showing the large variation, so you can even calculate how many hours of steady illumination with different intensity lights you need in order to match the total photon flux (or foot-candle hours if you wish) from the natural light.