Flourescent Lighting
 

I have Cattleya's Phals, & Dendrobiums under 4 32 flourescent tubes. How close should the plants be to the lights? I ask this because some of my plants have yellow leaves and I am wondering if it's too strong light.
Linsoo

They should be very close to the lights but the flourescent lights will not turn leaves yellow, that is something else. Some of my larger orchids are actually touching the tubes and are unharmed. Inspect your plants for pests, that could be your yellow leaf problem.

Fluorescents should be 4 to 6" above your plants. When you have plants like phals in spike it makes it hard to keep them under lights. Unless you are using special tubes like are used in aquariums you will not have a chance of giving your plants to much light. The yellowing leaves could be lack of fertilizer or older leaves.

Jayme

I'm using just the CFL spiral bulbs and they are put 12 inches above the leaves of my phals. Even at that height I have leaves on 2 plants that are turning purple. I'm pretty sure it's the light factor because it's only turning purple on the areas where light hits it. Am I risking burn any day now?

I was under the impression that flourescent lights cannot burn plants at all, no matter how many or how close.
My orchids are varying heights from the tubes, some as close as an inch, and I have never had a leaf get burned. :hmm (I have 6 - 4' tubes tight together)

Are the lights you're using normal fixture lights for using around the house or some type of plant light?

That is very curious indeed. :scratchhead:

Chris

I have 4 phals and was using 4 spiral CFL's (27 W, 6500K daylight). Over a month, the leaves on 2 plants turned purple. When the one I was trying to rebloom started developing buds, I switched to 2 full spectrum spiral CFL's (5000K, 55W, CRI=80). I don't really understand why the other 2 haven't turned purple though. Oh well...

If your plants are turning purple is that a good thing?
Just wonderin because I have 4 23w CFL in a 3' x 1' 10" x 2' - 2' 8 space is this good enough or do I need more light? it is about 6400 lumens!

I really doubt this little bit of light is causing the purple. The goal isn't to get the leaves to turn purple just to attempt to provide a high quality lighting withing the range they can tolerate. The only way to determine what amount of light is there, is to get a high quality dependable light meter and measure it. Charts that I've seen are a quickie way, but hardly the final answer since so many things can affect the actual output. I run one 105watt CF and 2 55 watt CF in the same area. This is the actual wattage being drawn by the lamps. I only read approx 800 foot candles off the sides of the lamps. This is marginal for Phals and insufficient to bloom many others, but they grow ok. I don't get purple leaves on the phals.