Directions for Lighting Hydroponic Plants


Adding artificial lighting to your hydroponic garden allows you to grow indoors year-round. The most cost-effective lighting for hydroponic plants is a mixture of warm-spectrum and cool-spectrum fluorescent lights or commercial grow lights. These lights are suitable for small gardens and starting plants indoors. For serious indoor gardeners, the investment in a high-intensity discharge light system might be in order. Your plants need high-quality light in sufficient quantity to grow. The quality of light is determined by the wavelengths of light available to the plants. Plants need light in the blue wavelengths, or cool-spectrum, for vegetative growth and a small amount of light in the red wavelengths, the warm-spectrum, to stimulate flowering and fruiting.

Step 1

Set up your light fixture directly above the plants. Attach the lights with a chain or other adjustable system so they can be moved as needed.

Step 2

Turn on the lights and allow them to warm up for approximately 10 minutes. Place your hand under the lights and judge the heat of the lights at various distances from the light.

Step 3

Position the light as close as possible to the top of the plants without burning the plants. The closer the plants are to the light source, the more light they will receive. If your hand is hot, however, the plants will be too hot.

Step 4

Add reflectors, mirrors or aluminum foil on the sides of the plants to reflect the light back onto the plants.

Step 5

Group plants together according to their heights and lift shorter plants to keep them closer to the light. Place plants that need more light in the center of the light fixture and low-light plants on the edges.

Step 6

Put the lights on a timer, or manually turn them on and off at the same time each day. Run the lights for 18 hours daily during the initial vegetative stage. Reduce the lighting to 12 hours daily to induce flowering and fruiting.

Step 7

Install a fan or use air conditioning to cool the area. Keep the temperature less than 80 degrees F.

Step 8

Adjust the height of the lights as the plants grow to avoid burning the top of the plants.

Tips and Warnings

  • Leaves that turn crisp and brown are burned. Move the light farther away from the plant.

Things You'll Need

  • Lighting fixture and bulbs
  • Chain
  • Timer, optional


  • University of Hawaii College of Agriculture: Growing Plants Indoors Under Supplemental Light
  • Cornell University Cooperative Extension: Indoor Plants, Artificial Lighting
  • Iowa State University Extension--Reiman Gardens: Lighting and Houseplants

Who Can Help

  • Simply Hydroponics: Lighting Basics
Keywords: lighting hydroponic plants, artificial plant lighting, using grow lights

About this Author

Diane Watkins has been writing since 1984, with experience in newspaper, newsletter and web content. She writes two electronic newsletters and content around the web. Watkins has a Bachelor of Science degree in chemistry from Clemson University. She has taken graduate courses in biochemistry and education.