I have grown greens under lights this winter and I love having fresh lettuce and kale and mustard etc even when the snow is 3 feet deep outside. But I've noticed something strange. I sowed lettuce seeds and for reasons of space I set half under fluorescent and half under LED. The lettuce under fluorescent came out as usual, very normal. But the lettuce under LED grew very thick, leathery leaves, in tight small plants. What is happening? The lights have red white and blue LEDs. Have I set them too close? (about 8 inches).
Growing Under Lights
Certified GKH Gardening Expert
All brassicas, including lettuce have a slight sensitivity to the red spectrum. In defense, they will cluster really dense, and have thick leaves. You can experiment with moving the lights up a little at a time and this will help. If they start stretching really tall, you know you have moved them too far.
I use a KIND LED panel myself, but it is 750 watts and requires to be about 4 feet from lettuce. So you will have to find the "sweet spot" and take note of where the plant does best. I do think the lights are too close, though.