24 hour grow lights a bad idea?

Asked June 16, 2016, 5:25 PM EDT

Some of the seedlings we planted indoors seemed very stunted, despite (or maybe partly because of) 24 hour a day red and blue spectrum grow lights we used this spring. Now they are continuing to grow very slowly after 3 weeks and more of being transplanted in the garden. Is round the clock grow light hard on seedlings?

Hennepin County Minnesota

1 Response

We don't recommend using lights 24-7. Usually 16-18 hours per day is enough, and plants need some down time. It is also best if the temperature cools a bit during the down time.

It would be helpful to know what plants you are growing. Different plants have different light and growing requirements. For instance, tomatoes need lots of light and regular fertilizing while they are indoors. But many houseplants get by simply on ambient or window light.

For plants that need lots of light, the lights must be placed very close to the plants, but then moved frequently so that the plants don't ever touch the lights. Even then, plants such as tomatoes become leggy because of lack of light.

This is a good all-purpose fact sheet on growing plants indoors:
http://www.uvm.edu/pss/ppp/articles/lighting.html
This is a good source of information on starting seeds indoors:
http://www.extension.umn.edu/garden/yard-garden/flowers/starting-seeds-indoors/