Grow Light Guidelines for Getting Seeds Started

My Garden Life
January 15, 2024
Table of Contents
Starting your own seeds requires more than sticking them in a pot of soil starter mix. Besides adequate water, healthy plants need plenty of light. Grow lights allow you to start seeds indoors so that your plants are strong and healthy when it’s time to plant them outdoors.

Types of Grow Lights

Grow lights provide light ranges that enhance plant growth. They vary from standard fluorescent bulbs to specialized plant bulbs. Each type of light bulb has advantages and disadvantages. 
  • Standard fluorescent bulbs are less expensive, and many people already have them. They also stay cooler to the touch, so you don’t risk burning your plants.
  • Other specialized plant bulbs generate heat. They can be beneficial to keeping your seedlings at the optimal temperature for growth.
  • The color and intensity of light differ between bulb types too.

Seedling Daily Light Needs

basil plant seedlings

Leave the grow lights on for 14 to 16 hours per day to provide light for the young seedlings. It’s best to turn the light on early in the morning and turn it off around dusk. Your seedlings will still thrive if you deviate from this schedule. But it’s a good idea to get them used to the natural light pattern they will eventually experience outdoors. This decreases the risk of transplant shock later when you move them outside.

Pro tip: Refer to the seed packet to know when to start and move your seedlings outdoors.

Pro tip: An inexpensive plug-in timer is a way to turn grow lights on and off at the same time every day without remembering.

Grow Lights as Heat Sources

seedlings growing in pots

Keep the bulbs of the grow lights one to two inches away from the tops of the vegetable seedlings. The bulbs provide heat as well as light for the vegetable seedlings. Many seedlings don’t grow well until temperatures reach 70 to 80 degrees Fahrenheit. Placing a thermometer beside your seedling trays will help you determine if they are staying warm enough. If needed, buy a heat mat to place under the seed tray.

Grow Light Cautions

grow light structure with seedlings in pots

Some grow lights can get very hot and will burn or singe your plants if they are too close to the seedlings. Check the seedlings growth daily. Adjust the height of the grow light as needed to maintain the distance between the bulbs and the uppermost leaves. The thermometer mentioned above will help you determine if the seedlings are getting too hot (above 80 F).
Following these guidelines will help the seeds germinate and will grow healthy seedlings for your garden. Once the chance of frost has passed for your region, you should harden off your seedlings. Then, transplant them in their permanent home outdoors.

planting a seedling in the garden

When to Start Seeds Indoors

Timing is important when starting seeds under lights. Planting certain seeds late won’t allow enough time for the seedling to grow big for easy handling. But if you plant too early, the seedlings will be large and unruly. Check out our tips for creating a Garden Planting Schedule.


  1. Jessica Aaron

    will a 6000 lumens 60watt LED light work its 6500k so a white white light to grow plants?

    • My Garden Life

      Hi Jessica,
      It depends a little on what you’re growing. Seedlings prefer light in the range of 2,000-3,000 lumens getting started. 6500 lumens should be more than sufficient once they’ve put on some leaves, or for other types of mature plants you are growing. Depending on what type of fixture you’re using, you can vary the lumens by changing the proximity of the light to the plants. For example, raise or lower a hanging fixture to change the lumens per square foot. In researching your question, we found this video on The Rusted Garden site that you might find helpful.

  2. Keith

    My seedlings are leggy, even with a grow light.
    I found the information here very interesting, especially leave the light on for 14- 16hrs.
    Any more information on this please update me.

    • My Garden Life

      Hi Keith,
      We’re glad you found this information helpful. It sounds like your seedlings are stretching (getting leggy) to reach more light. You could benefit from some type of adjustable grow light set up, such as lights on chains or pulleys, that allow you to raise and lower the light system as your seedlings develop. It is a fine balance to determine how close to place your lights without burning your seedlings, but with experience you should find success.


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