Depending on the brand of bulbs and their lumen output the move to T8 might be at best a lateral one. In all likelihood it will actually be a retrograde move as far as light output is concerned. In no case would I actually consider it an 'upgrade'. If you cannot consider HO lights then you might want to consider CFL or somehow add natural light to the T12 setup.

H

Welcome back H! ;-)

I agree with what Howard says...

bob

Welcome to the forum chopster.

I bloomed many paphs, both leaf varieties, under regular T8 shop lights, including multiflorals like the rothschildianum. I also bloomed a couple of bulbos using them too, including Elizabeth Ann 'Buckleberry'.

The biggest question I have is how far away from the tubes are your plants. They must be within inches of the tubes. When new, the middle of the tube puts out about 1000 fc's and at the end of the tube, 700 fc. As the tube ages, the fc's drop off drastically and should be replaced at least every six months. You also need to run the tubes 14-16 hours a day.

Good luck and rest assured you can bloom many lower light plants under T8's until you can upgrade your light set-up.

Brooke

I've been able to bloom several lower light plants plus a b. nodosa under two T12's and two 24w (equv. of 150w each) with very little extra light from the windows.

Hey, welcome back Howard! How's things?????

Jane

Thank you all for such quick, great, if sometimes contradictory ;) input. I realize that differences in your opinions may be because I need to give you a few more details.

The plants I grow now are mostly Paphs and Phals and one Encyclia. The other plants IÂd like to grow are Bulbos, Oncidiums, Phrags, and some Vandas.

I have two small east windows that are getting pretty crowded and two shelf areas where the lighting is used. The shelves in question are non-adjustable wooden shelves and the area I want to light on each shelf is about 4 ft X 16 in. Total clearance is about 22 inches between shelves. Currently humidity trays and the shoplights themselves take up about 9 inches, cutting clearance to about 13 inches, and naturally the plants themselves would fill that clearance a great deal. Of course I can adjust the height of T12 and T8 shop lights to get closer to plants if need be, but I canÂt get any farther away than probably 1-8 inches from the tops of leaves, depending on the size of the plant.

If I did some more investigating into getting a T5 setup, as some of you suggest I should, my question would be: How far away do the tops of plants need to be from a T5 setup, especially low-light plants? Would low-light plants like Paphs and Phals actually be safe only 1-8 inches from a T5 set up?

Also, given the shelf area described above, would I be looking for a 2-bulb T5 configuration, a 3-bulb T5 configuration, or a 4-bulb configuration? (I am using a 4-bulb T12 configuration now and would also be using a 4-bulb configuration if I switched to T8s.)
If low-light plants could be safe 1-8 inches from a T5 bank of lights, certainly a T5 setup would give me more flexibility to grow other types of orchids as well, but that seems too good to be true and I donÂt want to jeopardize the plants I already have.

The way I am figuring it, switching to a T8 setup would allow me to continue growing the plants I have, some of them perhaps more successfully, and maybe one or two medium light species I canÂt grow in my east windows or under T12s--plus I would significantly save in energy costs over my T12 setup. A T5 setup in the same shelving configuration might be harmful to my low-light plants, though it would expand my capacity to grow higher-light varieties. Energy consumption with a T5 would be greater than with a T8 setup.

Please let me know how I might be misunderstanding things and if you would change your advice based on this info.

Again, IÂm so grateful you are willing to take the time to help me think this through.

Thanks,
Charlie

Hi Charlie,

Welcome to the board!
I don't think low-light plants like paphs need to be 1-8 inches away from a high output T5 (which is the only T5s really worth getting anyway) to bloom properly, and I've met many people who bloom paphs under T8s..whether or not they'd be 'safe' under T5s, I'm not sure.

The flexibility you get from T5s is a good point though, cause you can adjust how close or far your plants are depending on how much light you need - ie you'd be able to expand the range of plants you could grow. I have my higher light plants on little racks closer to the light, and my lower light plants further away, or even partially under the racks. These lights are a hefty investment though, so if you only want to make the low-light plants you have a bit happier, I would be hesitant to take the plunge. ;)

In regards to how many tubes to get, here are some measurements: a 4 tube fixture is around a foot wide, and 3 inches high, so should fit comfortably under your shelf. Then again, consider that T5s are quite bright so you could potentially get away with having two tubes mounted at the back of your shelf, and that way the area closer to the front of the shelf would be a little lower light than the back, creating for you a gradient with which to work with.

Just a note - there is some evidence suggesting that the brand of fixture you get for T5s can really effect the light output, due to different reflector qualities. There are pretty cheap ones (~70 for a 4 tube fixture) for sale these days..it would be interesting to see how they compare to brand name reflectors. I chickened out and went with a brand name one, and it's great...but I am always wondering whether I got gyped out of just using something cheaper.

My point was not that T8's are somehow bad or not good for growing but that they are not better than the T12's you already have. T12's are 40W per bulb and typical lumen values are 3000L to as much as 3300L per bulb. T8's are 33W per bulb and typical lumen values are 2400L to maybe 2800L per bulb. Yes they use less energy. Electronic ballasts being most of it. If one could find 40W T12 with electronic ballasts I would say buy it immediately and call it good. That is your value leader right there. But, again, only as a new customer, if you already have hardware for T12 don't scrap it for T8 or electronic T12. As mentioned you will pay to have the miniaturization possible with the T5 technology. To get the same amount of light with cheaper hardware you have to use CFL for some of the lumens. And, no, you can't hurt phals or paphs with T5's. They don't need the extra light but they won't be hurt by it. Unless you do something like put them 1" from four tubes and hit them with a 14hr run the first day they go under the new bulbs. But I am assuming you wouldn't do anything like that. Reflector efficiency is important but IMO not worth worrying about too much. At the 400W HID level or maybe the 125W CFL level a good reflector gives enough more light than a cheap one to be worth its price but at the T5 level I would just use 4 bulbs in a cheap fixture vs three (forget using two for any reason) in a good one.

H

Howard,

You bring up several things to mind at once.

First let me clarify what you are saying: given the clearance restrictions of my shelving, my paphs and phals could safely be an inch away from a bank of 4 T5s if I somehow introduced them slowly to the new light or reduced the amount of time they were lit? And eventually I could grow an Oncidium or Vanda alongside these Paphs and Phals under the same bank of four lights for the same period of time and all of them would thrive? That seems amazing to me, but if that is correct, well, T5s are definitely the way to go!

Or, if that is not the case, if I could find an electronic ballast T12 fixture, I should stick with T12s?

And, even if I switched to T8s to save energy, a 32W 86CRI 4100K T8, or even a 32W 90CRI 5000K or 6500K T8 bulb, would not give me the same plant benefit as full spectrum T12 bulbs? Wow!

More rethinking to do...

Thanks.

Currently you have paphs and phals 1-8" from T12 tubes (40W each), T5 tubes are about 55W each. The ends of the tubes are much less bright than the center and you have 7" of adjustment. I should think low light plants will be perfectly fine in such a situation. In fact, a Vanda might not do as well as you imagine but given that most Vanda's are actually part Ascocenda you should do fine but know that an Ascocenda is not the same thing as an Oncidium or a Cattleya for that matter. Under lights all of them are light deprived by default. Your run time will attempt to bridge the gap between natural amounts of light collection and the amount of intensity you can deliver with LID (low intensity discharge) light technology. So keep that runtime up around 14 - 16 hours regardless of what you have under the tubes.

H