Can seedlings get too much light? Yes.
A recent lesson learned: This is a photo from a couple weeks back, we got a new 100W Sansi LED floodlight and thought, "Wow, this super bright light is going to really get those peppers growing big before putting out in the garden!"
Well, not so fast. After a week under this bright light, we noticed that the leaves of our peppers were starting to turn purple and curl, and their growth just stopped. Too bright! I think this light would be perfect if a couple feet away, it's super bright!! But, if it's only 8" away, it's too much. We turned the light away but the damage was done.
It is true that your seedlings need bright light to grow healthy and strong—but, too bright a LED light could actually damage them if it's too close – plus, seedlings also need a period of darkness in order to thrive. Generally, pepper seedlings should receive roughly 12 to 16 hours of light a day. So turn off the lights and let them sleep! And, don't do what we did this year and burn them by putting your extra bright LED lights too close. Brighter isn't always better!
These poor burned seedlings above are still recovering outside now weeks later, and they still aren't looking too happy with us! No real new growth, and their leaves are still curled and purple. Hope they recover, but if not, that's ok, we started lots of other seedlings so we'll make do! But we still feel awful for nuking these little guys.
Another Seedling Tip Regarding Light:
Make sure to harden off your seedlings!
Have you learned any new things this year?
Remember, there are no mistakes in gardening, only experiments!