How to Grow With Metal Halide


If you live in a climate that's too cold to grow your favorite fruits and vegetables, you can try your hand at growing them indoors under artificial light. Not just any artificial light will do. Plants grown indoors require devices that emit light within an electromagnetic spectrum suitable for photosynthesis. Metal halide light bulbs emit an intense blue light that is essential to helping plants develop strong roots, stems and leaves in the vegetative stage.

Step 1

Find the square footage of your growing area to determine the wattage of metal halide bulb to purchase. Use a measuring tape to determine the width and depth of the growing area. Multiply the width by the depth to determine square feet. Multiply the desired watts per square foot--use 40 for full sun plants and 25 for partial shade plants--by the square footage of the growing area to determine the appropriate wattage. Round up, if necessary, to the next wattage increment.

Step 2

Purchase a lighting fixture that's compatible with the metal halide wattage you need to adequately light your growing area. Choose a reflector that's compatible with your grow light. Consider purchasing a grow light fixture with a switchable ballast that's compatible with both metal halide and high pressure sodium grow light bulbs.

Step 3

Set up your grow light fixture so it can be raised and lowered as your plants grow. Position 250-watt metal halide lights 10 inches above plants, 400-watt metal halide lights 12 to 14 inches above plants and 600-watt metal halide lights 16 to 18 inches above plants. Keep 1,000-watt metal halide lights at least 24 inches from the tops of your plants to prevent the tips from burning.

Step 4

Turn on your metal halide light and wait for it to warm up; this can take between 10 seconds and five minutes. Give your plants 16 to 18 hours of light per day. Consult the specific requirements for the type of plant you're growing to determine exactly how many hours of light to provide.

Step 5

Run a fan in your growing area to keep the air cool and circulating. This is essential to keep the area at a growing temperature that's comfortable for your plants.

Tips and Warnings

  • Always use lighting fixtures and bulbs that are compatible with one another. Trying to force fixtures and bulbs that are not compatible can result in an increased risk of fire.

Things You'll Need

  • Measuring tape
  • Calculator
  • Grow light fixture
  • Reflector
  • Metal halide bulb
  • Fan


  • Hydroponic Basics; George F. Van Patten; 2004
  • Harvard University: Metal Halide Lamps

Who Can Help

  • Greentrees Hydroponics: How to Choose a Grow Light
Keywords: metal halide light, grow lights, grow metal halide, grow plants indoors

About this Author

Megan Mattingly-Arthur has been writing professionally for 10 years. Her writing has appeared in various publications, including "Teen Voices" and "Positive Teens" magazines as well as the book, "The Young Writer's Guide to Getting Published." She is currently enrolled in the Travel and Tourism Specialist program at the Penn Foster Career School.

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