How to Compare Types of Artificial Light on Plant Growth


When you want to compare different types of artificial light for plant growth, there are a number of things to consider, the least of which are the types of lights. First of all, the growing conditions need to be exactly the same to give a true representation of the effect the artificial light will have. Secondly, each light must be maintained at the same height as the others so although wattage and composition of the bulbs may be different, the plants will receive roughly the same amount of light. Thirdly, the plants must be the same type.

Step 1

Pot as many plants as you wish to carry out this comparison, by putting them in soil and watering thoroughly. Lettuce or radish plants grow quickly and make a good test subject, but realistically, any plant can be used as long as it is allowed to grow exactly the same way as the others.

Step 2

Place each potted plant into a 4-foot high cardboard box on top of either patio bricks or books. Multiple bricks or books will make it easy to remove one at a time to keep the plant at the same level as it grows. The boxes at this height will limit outside light from affecting the growth of the plants. Use your tape measure to get a measurement of 24 inches from the top of the plant to the top of the box.

Step 3

Place your choice of grow light on top of each box so that it beams directly down onto every individual plant. You can use any or all of the suggestions listed, one for each box, and the wattage of each bulb will give roughly the same amount of growing brightness at the 2-foot height.

Step 4

Give each plant the exact same amount of plant food, water and light. The lights should be left on for 16 hours per day, and turned off for the remaining 8 hours.

Step 5

Observe plant growth over a two- to three-week period in each box, longer if so desired, then measure the final growth after the allotted time has elapsed. The plants that grow the tallest and leaf out the most will be the ones that are doing best under a particular artificial light.

Things You'll Need

  • Plants (lettuce or radish are preferred)
  • 150 watt incandescent grow light
  • 200 watt CFL light
  • T-5 single fluorescent bulb, 54 watts, 4 feet long
  • 250 watt high pressure sodium light
  • 250 watt metal halide light
  • Cardboard boxes, 4 feet high
  • Pots, soil, water
  • Patio bricks or books
  • Tape measure


  • Little Green House: Indoor Plant Grow Light Guide
  • Cornell Education: Plant Growth Experiments
Keywords: artificial light, plant growth, wattage and composition, lettuce or radish, grow light, observe plant growth

About this Author

Dale Yalanovsky has been writing professionally since 1978. He has been published in "Woman's Day," "New Home Journal," and on many do-it-yourself websites. He specializes in do-it-yourself projects, household and auto maintenance and property management. Yalanovsky also writes a bi-monthly column that provides home improvement advice.

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