How to Plant Seeds With a Heat Lamp


Starting seedlings under lights inside gives them a chance to grow strong before planting outside. It also lets you start tender vegetable plants indoors while temperatures outdoors are still too cold. Some plants, such as peppers, love heat and warm soil, and air temperatures are necessary for the seedlings to grow properly. Heat lamps provide the warmth and light required for these types of plants. Use them to supplement normal grow lights, as using them exclusively may burn and damage plants.

Step 1

Fill a seed starting tray with soil-less potting mix. Water the mix until it is evenly moist throughout.

Step 2

Sow seeds 2 inches apart in the tray, following the planting depth instructions on the seed packet. Sow most seeds to a depth twice their width, though some heat-loving seedlings require light to germinate. These should be sown directly on the soil surface then lightly pressed against the soil with a fingertip.

Step 3

Set a soil thermometer inside the tray. Wrap the seed tray in a plastic to bag to preserve moisture during the germination process.

Step 4

Position the heat lamp 8 inches above the tray and turn it on. Maintain a soil temperature of 75 to 80 degrees F, or what is recommended on the seed packet. Turn off the light as needed when temperatures climb above this threshold and turn it back on when they begin to drop.

Step 5

Remove the plastic when the seedlings appear. Place the seedlings 6 inches beneath a grow-light fixture for 16 hours a day.

Step 6

Supplement the grow lights with the heat lamp to maintain the proper soil temperature. Heat the soil in the evening hours when temperatures are cool with the heat lamp and with grow lights during the daytime when room temperatures are higher.

Tips and Warnings

  • Keep the soil moist at all times, as the heat lamp will dry it out more quickly. Heat lamps can overheat soil and cause the plants to die. Check on plants regularly when the light is in use to ensure the proper temperature is being maintained.

Things You'll Need

  • Seed tray
  • Potting mix
  • Plastic bag
  • Soil thermometer
  • Heat lamp
  • Grow lights


  • University of Arizona Extension: Starting Seeds
Keywords: planting with heat lamps, growing under lights, seed starting

About this Author

Jenny Harrington is a freelance writer of more than five years' experience. Her work has appeared in "Dollar Stretcher" and various blogs. Previously, she owned her own business for four years, selling handmade items online, wholesale and via the crafts fair circuit. Her specialties are small business, crafting, decorating and gardening.