Artificial light quality

[moniluhum]

I have several Phal orchids both in greenhouse and under artificial lights. It appears that those under artificial lights have healthy roots but their leaves appear to be less healthy than those in the greenhouse. Could it be that the lights are too close? What could be causing this problem?

[BigSteve]

Could the lights be the sole reason for the plants lack of leaves , i suppose so.My Phal's tend to have less leaves than the 1's i have given to friends & family, they grow in windowsill',s , me under lights & in the greenhouse.I believe the plants require less leaves under my care because they have plenty of light all year round & my hybrids tend to grow a new leaf then spike, this can be twice or three times a year.Whereas my friends/familys Phal,s tend to spike once & maybe grow a couple of leaves in between flowering.
Reducing the light(less hours/lower levels) under lights may make the plants grow more foliage to compensate but also a change to other growing variables may achieve the same.
Personally if the plants under lights are healthy & still flowering then i wouldn't worry about them to much , maybe give them a holiday in the greenhouse every now & again.

[raybark]

It may be that you have them too close to the lights, affecting the plants in potentially two ways.

Excessive light levels can actually decrease the flowering of many orchids.

And, if the light intensity is to great, it can overheat the leaves, disrupting the chemical processes that go on within them.

[Missanna]

First off, as a lights grower myself, it is hard to give any advice without knowing some more information:

what kind of lights are you using? (T12, t5, HID etc)
How many bulbs and how long are they? (Assuming you are using fluorescents)
What is the distance from leaves to bulbs?
What is your photoperiod?

I'm sure I will have more questions after you answer those.

Also, Ray brings up a good point: you need to feel the leaves after the lights have been on for a few hours. If they are even sightly warm to you, they are too warm. Remember that our outer body temperature is about 90 degrees which is too hot for the leaves.

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Also do you have more photos of the orchids you do have under lights?

[moniluhum]

The lights are t5 Hydrofarm. There are 4 bulbs that are I think 24 inches long. The distance is about 20 inches and the light period is about 12 hours.