Question
Hi Will:
I have a plant room/greenhouse in my home. I have used flourescent growth lights in my room in place of regular lights but it is difficult to evaluate what effect they are having. They seem to help the plants that grow a few inches under the lights, but I also use them for large plants that grow to about 3' from the lights and I have a growth spot light about 3 ' over my fish pond (water lillies, umbrella plants, etc.) Should I expect any results from plants this far from the light source ? The light tube directions say to place the tubes 6" to 1' from the plants. This would not be too practicle under my greenhouse conditions.    Any suggestions or ideas will be appreciated. Thanks in advance for the help.   

Bill Bollaert

Answer
Hi Bill,

The light from fluorescent tubes drops off rather dramatically as the distance from them increases. "Enough" light depends on the plant species as well as the distance from the lights. Medium light plants should be within a foot or so of the tubes. Low light plants can be 3 to 6 feet away.

All plants have a range of acceptable light. At the low end of acceptable light, plants will survive but grow very slowly and with thinner stems and smaller leaves.

For best results, use low light plants in your greenhouse. Of course, adding more fixtures will increase the light. If you can place reflective material (mirrors, white surfaces, for example) in strategic places that will help you maximize the available light. Older fluorescents emit less light, so it is best to change the tubes every year or two. Finally, I recommend that you keep the lights on for 16 hours per day.

Please let me know if any of this is unclear or if you have any additional questions.

Regards,
Will Creed, Interior Landscaper
Horticultural Help, NYC

You can E-mail me directly at: [email protected]

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