How to Compare Artificial Growth Lights to Sunlight for a Plant


Lack of adequate light is a limiting factor that prevents houseplants from growing well in your home. Unfortunately, most windows in a home are either too small or not positioned correctly to allow plants enough light to grow. One way to supplement light from a window is with fluorescent lights, LED lights or plant grow lights. Before growing a light under an artificial light, you must first assess whether your lighting scheme will replicate the amount of light a plant receives in nature.

Step 1

Read the labels of plant lights before installing them in your home. Sunlight provides the full spectrum of light, while various bulbs only provide certain spectrums of light that a plant may need to grow. For example, incandescent bulbs will provide enough red spectrum light for plants, but will not provide light in the orange, yellow-green or blue spectrums. Daylight-balanced or white fluorescent lights will not provide sufficient light in any of the various spectrums, while cool white fluorescent lights provide sufficient light in all light spectrums except for red. Plant lights provide sufficient red light to supplement a cool white fluorescent tube. According to the University of Missouri, you should use one 30-watt incandescent bulb with every 100-watt fluorescent bulb or one plant grow light per every one cool white fluorescent tube that you use in a plant growing system.

Step 2

Average the amount of light that a plant receives in nature by taking a reading in that location with an ambient light meter eight times in a day. Add all the measurements together and divide by eight for the average amount of light in foot candles that a plant receives.

Step 3

Measure the light amount in foot candles that your plant will receive in its location in your home using the ambient light meter.

Step 4

Add supplemental lighting by moving lamps near the plant. Add grow lights, fluorescent lights or a mixture of cool white lights and incandescent lights to the fixtures. Measure the light quantity in foot candles with the ambient light meter. Continue to add supplemental light until the measurement in foot candles matches the lighting average measurement for the plant's location outdoors.

Things You'll Need

  • Incandescent light bulb
  • Plant grow light
  • Cool white fluorescent light
  • Light meter that takes measurements in foot candles


  • University of Missouri Extension: Lighting Indoor Houseplants
  • University of Iowa Extension: Lighting & Houseplants
  • Texas A&M Extension: Growing Phalaenopsis

Who Can Help

  • North Carolina State University: Indoor Plant Selection and Care
Keywords: measuring light intensity, selecting grow lights, houseplant care

About this Author

Tracy S. Morris has been a freelance writer since 2000. She has published two novels and numerous online articles. Her work has appeared in national magazines and newspapers, including "Ferrets," "CatFancy," "Lexington Herald Leader" and "The Tulsa World."