50W Blue grow light build for seeding

According to my research, blue light is primarily used in plants for vegetative growth.  It follows, therefore that blue light is best for seedlings and clones that you want to grow in size quickly.  Is this logic sound?  I’ll experiment, and report back.

This video is a live build video where I make a $54 dollar blue-only grow LED floodlight.  Note that at the time of posting, the floodlight price has already changed on Amazon.  You can typically find these on ebay for a reasonable price.


Total Cost: $54

2 thoughts on “50W Blue grow light build for seeding”

  1. Thank you for sharing. One question. With a 50 watt bulb is that going to be to much light when placed above a seedling tray or is there more for the greenhouse or larger gel rowing area? I to have many of the ML gardening recommendations including the green house, seedling boxes,and irrigation. I have the heat mat as well as 2 bulb fluorescent light for the seedlings. I would like to use something more cost effective in thr long run. Is the 50 to much? Or something for greenhouse or day kratky method or hydroponic in a basement? Thank you

    1. I’m using a 50W for seedlings right now and it appears to work fine. It sits about 1ft above the plants. Check out my latest post on sizing LEDs according to CO2 consumption. While you probably won’t measure CO2 consumption for seedlings, the 16W/m^2 rule can apply to seedlings as well. You just want to keep it far enough away that there won’t be too much heat. A seedling will absorb all the red/blue photons, but it can only use so much to break down CO2 and make glucose. The rest becomes heat.

      I’ve also grown spinach, kratky-style with a 50W and a 20W LED.

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