How to Start Plants Under Fluorescent Light


Starting seeds indoors under fluorescent lighting allows you an early start on the growing season. It is also a good way to produce transplants of heirloom or special hybrid seeds. Plants need water, air, warmth and light to germinate and grow to transplant size. Start seeds 4 to 12 weeks before the last frost date. Plants started too early will outgrow the container and will not be healthy at planting time.

Step 1

Purchase a sterile potting media containing pine bark, sphagnum peat moss, perlite or a combination of these. Water the potting media before beginning. It should be moist, but not wet.

Step 2

Fill seed trays or pots three-quarters full with moist potting media. Smooth the top and firm the surface of the medium.

Step 3

Sow small seeds, and seeds requiring light to germinate, in rows directly onto the surface of the medium. Make furrows for medium and large seeds in the planting trays 1 to 2 inches apart, following package directions for the recommended planting depth for the seeds. Form a small hole if using pots.

Step 4

Place the seeds in the rows or holes and cover them gently with potting media at the recommended depth, or at a depth of about two to four times the diameter of the seeds.

Step 5

Water the newly planted seeds with a fine mist of water or set the containers in a tray containing 1 inch of water. Saturate the media, then allow the containers to drain. Continue watering daily as needed to keep the growing media moist, but not wet.

Step 6

Cover the seed trays with the clear plastic dome, if available, or cover the trays loosely with plastic to maintain humidity. Keep the plastic cover until the seeds germinate.

Step 7

Remove the plastic and place the trays or pots under two 40-watt cool-white fluorescent lights, or plant grow-lights. Place the lights about 6 inches above the plant canopy and light for 16 hours a day.

Step 8

Fertilize the seedlings after germination with a solution of water-soluble fertilizer diluted to one-quarter to one-half the normal strength. Continue fertilizing once a week with this solution until the plants are moved outside.

Step 9

Raise the lights as the seedlings grow, keeping the lights about 6 inches above the top of the leaves.

Step 10

Transplant seedlings grown in flats into individual pots of moist potting media (or a cell pack) when the first true leaves appear. Gently dig up the seedlings with a blunt knife. Use a pencil or stick to punch a hole in the media deep enough to accommodate the seedling at its original depth. Grasp the seedling by the leaves and place it into the hole. Firm the potting media around the plant.

Step 11

Move the plants outdoors to a protected area for a few hours each day approximately two weeks before planting outside. Increase the time outside daily until the plants are able to remain outdoors all day. Do not leave plants outside during windy weather or in temperatures below 45 degrees Fahrenheit. Plant the seedlings in the garden at the recommended spacing after the last frost date.

Things You'll Need

  • Seeds
  • Fluorescent lights
  • Seed tray
  • Starting medium
  • Peat pots, optional
  • Blunt knife
  • Small pots or containers
  • Potting mix
  • Water-soluble fertilizer


  • NC State University Extension: Starting Plants from Seeds
  • University of Illinois Extension: Growing Transplants
  • University of Tennessee Extension: Growing Vegetable Transplants for the Home Garden
Keywords: start plants indoors, grow fluorescent lighting, growing transplants indoors

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.