Artificial Lighting Question

[grandmapenguin]

Can anyone refresh my memory as to length of time that the Artificial light should be on by months One time I found an article and it said 18 hours during I think January thru March.
Can someone enlighten me on the full year

[mehitabel]

You can more or less choose how long you want to leave them on, as long as you give 6 hours or more of darkness. (And some people believe the research indicating plants need darkness is flawed and you can give light 24 hours/day)

Lots of people give 16 hours year round. Some decrease the time gradually in fall and increase again in spring. I give 18 hours year round and get good growth and spiking.

It's your choice.

[PocoGigio]

This schedule came from the 1988 All About Growing Orchids (an AOS endorsed Ortho book). My plants are under lights from Sept thru May using this schedule. Then, outside for the summer except the cool ones stay under lights. They recommend "advancing the season" if you grow strictly indoors. Something about avoiding the hottest days and getting plants to bloom for the holidays. Here it is, verbatim from the book:
November-January 16 hours/day (spring)
February-June 18 hous/day (summer)
July-August 16 hours/day (fall)
September-October 12 hours/day (winter)
Change lengths over a few weeks instead of all at once. This book is 22 years old but it works for the chids for the past 4 years. They're under 2 1000watt metal halide lights in a 8' x 18' greenroom in the basement.
Paula

[mayres]

I'm basically on mehitabel's noted schedule - 16 hours per day year round! Seems to work OK. I did find that paphs are photo sensitive to length of daylight and needed to NOT use this schedule for them to spike - my other plants seem to be OK with it.
There is indeed a lot descrepency among growers and so called "experts" about what works and doesn't work - like many things - we get to sift through it all and find what works for our conditions and the types of orchids that we grow.
Part of my thinking is that the majority of orchids live in the equatorial zones with little change of length of day year round - though they do note a period of decreased "intensity" of light during the rainy season.