Too much light for Phrags?

[terryros]

I have seen some pretty yellow leaves on some posted Phrag pictures of specimens blooming and doing well. With indoor wide spectrum fluorescent lights do you think there is any way to give Phrags too much light? I am not talking about burning them by touching the tubes but if they are at least 3-4 inches away and getting 16 hours of day length during plant summer should I care if some plants are beginning to get a slightly yellow tinge to the leaves?

[Ross]

I posted a thread a while back explaining the diff between natural light in nature or a greenhouse and steady output light from florescents or HID lights. First I would never place high intensity lights such as HID or t5 florescents that close to a Paph, Phal, or Phrag. Check these posts Affect of artificial light on Orchids A summary thread on lighting

I postulate (I have proven it to myself, but others seem slow to jump on the bandwagon ) that 12 hours of steady 1000 foot-candles light is not the same as a peak of 1000 foot-candles at noon in a greenhouse. In nature, light starts dim at dawn and slowly increases during the day to the daylight peak (even on cloudy days) then slowly wains to nothing as the sun sets. We blast the plants with a steady light source for the time the lights are on then abruptly turn them off. In the vivarium world there are folks providing something called a "dawn simulator". This is a system that simulates the transition I just descibed.

Now to your question. Yes I think you can fry a Phrag with a wide spectrum florescent 3-4 inches away over a long period of time. If, somehow the light were slowly rotated so that it moved from, say, 36" away in the morning up to 3-4" at noon to 3PM then slowly retracted to 36" at night, that would simulate natural light. Impractical, so we normally opt for another way to do it more to our daily routines. For my plants, I measure 800 FCs at the leaf surface for 12 hours. I get very nice natural light green foliage and nice blossoms. I have also fried plenty of normally high light plants like Encyclias with too-close lights. Hope this (long) post helps.

[terryros]

Very helpful. With my light meter set to the fluorescent setting (I use standard tubes - Verilux WS) and because the fixture in question has narrowly spaced tubes, I measure 1,000 to 1,200 fc at the leaf tops in the growing space. This is about 6-8 inches away from the tubes. If this is present for 16 hours per day do you think that will be excessive? I know that the great majority of orchids do not have that wide a natural variation in day length but had thought that we needed to increase the length substantially to make up for the lower quality of light. Maybe my 16 hours is excessive?

[dave b]

That light level (1000 - 1200 ft candles) is quite low for phrags. Thats the lower levels given for phals. Most Phrags can take very high light, even some full sun. Put you light meter in full sun at different times of
the day and see what you get. Im not advocating full mid day sun in the middle of summer. My point is that though you can grow phrags under flourescents, i sure wouldnt be worried about hurting them. Over the winter, i grew mine under bays of 4 4foot tubes (not compact flourescents, but tubes), and didnt care if the leaves were 1/2 inch away. I got them as close as possible due to the low light levels of flourescents. In the summer, they go outside in partial shade, but do get full sun in the morning and evening, and even dappled sunlight during the day through the trees.
They love it, and grow like weeds that time of the year.

[terryros]

I will stop worrying and let them be close. I am assuming that you don't do this with Paphs and Phals or do you think they can also be pretty close without worrying about them growing or blooming funny?

[dave b]

Originally Posted by terryros

I will stop worrying and let them be close. I am assuming that you don't do this with Paphs and Phals or do you think they can also be pretty close without worrying about them growing or blooming funny?

If your using standard 40 W (T12 or T8), 4 foot tubes, i wouldnt worry about the paphs or phals. For every 12 inches away from flourescents you get, the light decreases drastically. Thats why its recommended to stay within several inches of the bulbs. In fact, paphs and phals are perfect for growing under flourescents due to their lower light requirements. The only case where this might not apply, would be some of the newer high output T-5 bulbs. They are higher output and may even be warmer to the touch, but i dont use them and cant speak on their use.

[Ross]

Originally Posted by dave b

If your using standard 40 W (T12 or T8), 4 foot tubes, i wouldnt worry about the paphs or phals. For every 12 inches away from flourescents you get, the light decreases drastically. Thats why its recommended to stay within several inches of the bulbs. In fact, paphs and phals are perfect for growing under flourescents due to their lower light requirements. The only case where this might not apply, would be some of the newer high output T-5 bulbs. They are higher output and may even be warmer to the touch, but i dont use them and cant speak on their use.

t5 light banks are a new breed. The light output is way higher than either the t8 or t12 fixtures. That's why I went into my discussion above. The modern high output coily CF bulbs (not the Home Depot or Wal Mart type) are just as high light and just as much to blame for too much light under really close conditions.

[terryros]

I appreciated your information and had seen most of it before. I think the T5s would generate too much heat for me in my basement plant room with one outside window that I don't want to have open except for the Fall cool down. I am going to see this year whether the old standby WS fluorescents will bloom Catts if I have them close enough and have great conditions otherwise. I guess it is going to also be a test of the Phrags as well. I know that I do pretty well with Phals and Paphs. Scientifically I think we are all talking about whether the light a plant receives is a total quantity area under the curve issue (which constant fluorescents for longer day length might solve) or whether it is about the peak intensity that a plant receives during a certain number of hours. I may have some Catts and Phrags to give away if it is about peak intensity.

[boytjie]

Hello, everyone! This is my first post to the board. Fairly new to the hobby here, but quickly (frighteningly quickly, actually) becoming smitten. My question might have been answered before, but a search failed to turn up a definitive answer. I have a bank of 4 T5 tubes over my growing bench - Paphs, Phals, a Brassavola, an Aerangis, and a BLC. What's the optimum distance from the tubes to the top of the plant? I know Phals and Paphs need slightly less light. Thanks for the assistance!