Question
Will, Hi.  Do normal home lights, incandescent and fluorescent, help plants grow indoors, or only grow lights help?

Answer
Hi John,

You ask a good question because there is a great deal of confusion about using artificial light for plant growth.

Incandescent (and halogen) bulbs produce light in the wrong part of the light spectrum to be beneficial to plants. There are some incandescent bubs that are color corrected and sold as plant lights, but I still don't recommend them because all incandescents produce a great deal of heat, use and waste a lot of energy and are very expensive to operate over a long period of time.

Standard warm and cool white fluorescent bulbs do produce light in the right spectral range for plant growth. In addition, they do not produce much heat, are more energy efficient and are relatively inexpensive to operate. For most home uses, they are the best choice for using with plants. Fluorescent broad spectrum or "grow lights" also work very well, but they are more expensive to purchase initially and don't add significant benefit over standard fluorescent bulbs.

If you are using artificial lights alone (no natural light), then the lights should be as close as possible to the plants and should be on for a minimum of 8 hours per day. Plant photo-sensors are on the top surfaces of leaves, so the light can only be beneficial if they shine from above. Floor lights shining up are of no value for plant growth.

Finally, I will note that even the best artificial light is adequate for only low light plants. For plants requiring medium and high light, artificial lights can only be used as supplements to natural light.

I have written an article on light for plants that I will email for free to you (or anyone else) who sends a request to me at [email protected].

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

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Regards,
Will Creed, Interior Landscaper
Horticultural Help, NYC

Visit my website at: A link to HorticulturalHelp.com