Hopefully Howard will chime in as he is our expert 'light grower.'

I see you live in Iowa. I'll give you a short answer because your set up sounds similar to mine. I grow most of my orchids in my West windows from fall through winter. The room is very bright and plants are layered depending on their ability to take direct sun.

In summer, the high light plants go outdoors and work up to almost direct sun most of the day - east, south and west. They are on a high deck where they get sun all day.

Lower light plants go in east windows or on the eastern side of the deck.

Indoors over winter, the high light plants Catts, dens get west windows with supplemental CFL's for approx. 12-14 hrs.

Growing this way, I must take advantage of the spring/summer sun/light to get them ready to flower in the fall. The lights just keep the momentum going so I get blooms. I have not been able to initiate strong enough growth over winter to get spring blooms. (Catts & Dens) I would need stronger lights.

I can get flowers from the Oncids with supplemental light and many with just West window light over winter.

Hope this helps.

Jane

I am not an expert. That out the way, lets look at some orchids in nature. High elevations for the most part, several hundred to thousands of feet. High up in tree canopy, couple hundred feet. Light canopy coverage, constantly moving branchlets overhead. Equatorial locations, consistent 12 hour light period virtually year round. If you get from that that a longer rather than shorter period of light is required you would be right. Situations like our east and west window locations are unknown and are not dealt with well for the most part. Light will be too intense for too short a period of time. Under lights the situation is vastly improved but the lights need to have a minimum intensity of around 500fc for phals and ~1000fc for anything considered medium light. ~2000fc would not go amiss for high light types. At these kinds of intensities 12hr is absolute minimum, 14hr, much better and 16hr best. Going over 16hr brings you past the point of diminishing returns, plants need to sleep like you do. Not surprised the T5 'only' do 1800fc they are 'only' high output not 'very high output'. And no, they won't do anything beyond what they are rated for, there isn't any intrinsic benefit to being T5 vs T8, all the money buys you is miniaturization, the tubes are thinner and the fixtures sleeker. High output T8 are available and will be just as bright as T5 at lower cost... if you can find them. For a closet I can't imagine doing better than finding one of those rolling clothes racks that the better hotels roll your hangables on and hanging a couple or three CFL or Wonderlite from. At floor level will be all the light you could want depending on what you want to spend for bulbs and kilowatt hours to run them.

H

Howard,

You write, "Under lights the situation is vastly improved but the lights need to have a minimum intensity of around 500fc for phals and ~1000fc for anything considered medium light. ~2000fc would not go amiss for high light types. At these kinds of intensities 12hr is absolute minimum, 14hr, much better and 16hr best."

It's good news. Nearer my T8 bulbs I can get around 1000fc and I've been longing to grow something besides Phals and Paphs--though I'm fond of them still. Just growing pains. Can you give me an idea of what you mean by "medium light" plants--different people seem to mean different things by phrases like this. Do you mean plants commonly rated between 1500-2500 fc? Less? More? A neofinetia? A tolumnia? A cattleya? An oncidium?

I bloom oncid hybrids phrags, and smaller catts under 125 watt CFL's, on 12 hrs/day, during the winter. I use T-8's for phals and paphs. If there is any way you can put your plants outside during the summer, that's one of the keys to success. Mine only get a few hours of full sun during the day, the rest patchy thru tree leaves. But they put on twice as much growth during 4-5 months of warm humid summer outside than during the rest of the year under lights indoors. Many put on their growth and fatten up on carbs, and then when i bring them in and put them under lights, they come into bloom.

They can get some leaf damage from weather and insects, and something keeps eating the bud off my oncid papilio, but otherwise they benefit so much from the fresh air, higher light, warmth and humidity, that there is just no comparison to what I can give them inside.

Chopster you are just going to have to dive in and try various plants and go by the recommendations for the individual plant. Remember, the recommendations are geared to natural light, normally.

A book I recommend is William Cullina's Understanding Orchids. It is valuable because within each genus he gives recommendations for growth, including under lights.

You have your new light meter so when you get your new T5 set-up you can gauge the fc's from it, plus your T8's and the various windows available. Then you will be able to try different plants and how much success you have blooming it.

I know you are looking for a formula but I don't think one exists. Buy the plant, turn on the lights, run for 16 hours a day and then make appropriate adjustments. Everyone that grows orchids makes adjustments - you learn as you grow.

Brooke