Amy,

12-13 hours/day from mid-September to early-mid November, 15-16 hours/day the rest of the year.

HTH,

Bob

Similar to Bob's, though my "winter" is longer and not at the same time -- 12-13 hours from October to the end of February, 14 hours from March to May, 16 hours from June to the end of August, and 14 hours in September and October.

Julie

I am bad I give about 16ish hours a day year around, except in the summer they are near a window so they get 16 hours like they always do, but the midday time period is supplemented with sunlight.

I can't wait to be in a situation that I can take them outside for the summer.

I run them about 12 hours through the winter, and move it up to about 14 in the summer.

awesome. thanks everybody :)

It actually comes down to the numbers. Phals are commonly believed to need between 1000 and 1500 footcandles on average for an average day. For any number of reasons a day might be less than 12 hours but it can never be longer than that in ANY part of the world where phals grow naturally. So lets use 10 hours and 1000 foot candles to make the math easier. 10(h) X 1000(FC) = 10,000FC/dy. A four tube fluorescent fixture can probably deliver 1000FC so, if phals are all you grow then a 10 hour run time of four tubes year round will be all you need. Thing is, it would be the rare four tube fixture that could deliver 1000fc to all parts of the coverage area. The light out towards the end of the tubes might be only half as much, also, depending on their genetics many phals actually need a skoosh more footcandles than 1000 so if you added a couple of hours and made a 12 hour run time, again year round, you would be in good stead.

Now lets take an Oncid as an example. Oncids are commonly described as needing 2500 - 3000 footcandles, again for around 10 hours. 2500 x 10 = 25,000FC/dy. Right away you can see that a four tube fixture will have to run all day and all night to put 24,000 into the plant. Unfortunately plants need a lights out period to process the energy that they collect during the day. If you get from this that you cannot grow Oncids under tubes alone you would be correct. This is the point where the naysayers say: "well, I have only a twin tube fixture and I bloom Oncids all the time". Do you really? Did you actually have the oncid in nothing else other than artificial light from one bloom to the next? Very likely not. Either the plant was purchased NBS with a lot of the footcandles already in the bank or there was additional window light boosting the amount of delivered footcandles or for some part of the year, usually summer, the oncid grew outdoors. But wait, all is not lost. If you can get the output of the four tube rig boosted another 500FC over the spot where an oncid is growing 1500(FC) X 16(H) = 24,000FC/dy. Close enough for government work as they say. You can see that these run times are completely independent of seasonal adjustment. Seasons as they exist in tropical and sub-tropical areas do not involve large changes in daylength the way they do in North America and Europe. They mostly involve changes in the relative amounts of rainfall.

I would be remiss, since I've gone this far into it, to not discuss that minority of plants that require changing daylength in order to bloom. Some Cattleya are about all that come readily to mind but there are others. Thing is, they are very, very much a minority of the orchids that we usually grow and just as if you had a Poinsettia or Christmas Cactus you wanted to re-bloom you would probably deal with it as an individual, rather than adjust the light cycle of your entire collection to suit the needs of just one or two plants.

So, in summary, if you want to know how long to run your lights you have to know how much on average the same plants usually receive per day, then you have to know how much light in footcandles you lights produce and whatever number of hours it takes to get your lights to produce that number of footcandles is the proper runtime. Of course there is considerable variation, both in the plants and in light equipment. This means you don't actually have to know everything to the last decimal place but it does mean that if you have an Oncid under four tubes in a basement and it isn't blooming after three years it wouldn't be reasonable to blame anything else other than light for the lack of success. I haven't even touched Cattleya's and Cycnodes and other species that are highly variable. Some need tremendous amounts of light and will mandate some kind of CFL or HID or natural light combination to do well.

H

wow... thanks howard! that was very informative. brought a lot of things to my attention that i had not considered