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LED grow lights, distance away from plants and dim feature #766102

Asked August 06, 2021, 2:45 PM EDT

Hello! I started using new LED grow lights for vegetable seedlings this spring and have a couple of questions regarding their use. My lights are: SPIDER FARMER SF-1000 LED Grow Light Use with Samsung LM301B LEDs Daisy Chain Dimmable Full Spectrum Grow Lights for Indoor Plants Veg Flower Greenhouse Growing Lamps with MeanWell Driver My research says that I should have the lights 15 to 42 inches away from plants; for seeds and sprouts 24-28 inches away. Is this distance correct? I also used heat mats for the first time this spring and set the temperatures to preferred germination temperature of the seeds. I have used fluorescent lights in the past and had uneven results this spring as I was learning about the LEDs. I wasn't sure how to best use the dimmer feature, should I run the lights at 100% or dim them and if so, what is recommended? I would be interested in Instructional resources specifically using this type of LED lights. Thank you, Linda Dobbs <personal data hidden><personal data hidden>

Washington County Minnesota

Expert Response

I use LED lights and love them. My lights have an output of 6500K or the same as full sun. I put seedlings 2-4 inches from the lights and keep moving the lights up as the seedlings grow. I move them farther away if they bleach and look too light green. I experimented to find the right distance. I haven’t had any leggy seedlings since I started using LED lights. I also have a small fan that I blow across the seedlings to strengthen their stems and reduce fungal diseases.

I looked over the information available and how to grow seedlings under LED s and it is contradictory. I strongly advise experimenting and discover what gives you the best results with the potting mix, kinds of seeds, temperatures and the amount you water, each parameter influences the result. Gardening is very forgiving and customizable. 

https://www.gardeners.com/how-to/gardening-under-lights/5080.html

https://thisismygarden.com/2021/02/start-seeds-with-led-lights/

https://joegardener.com/podcast/seed-starting-part-3/

https://www.johnson.k-state.edu/lawn-garden/agent-articles/vegetables/lighting_options_for_Seeds.html

Evelyn Locke, MN Master Gardener, Tree Care Advisor, Volunteer Replied August 06, 2021, 3:14 PM EDT

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