I have some theories about growing seedlings indoors. Not sure if some of them have any merit, but that never stopped me.
The first theory though, I’m sure of. Seedlings need a lot of light or they get leggy. I keep my lights 1″-2″ from the tops of the plants and run them for 14-16 hours a day. It takes a lot of light to pretend you’re outside!
The second theory, I’m not positive about, but it seems logical. Some folks brush their seedlings with a hand a few times a day. I have a small fan blowing. Same principle. Slightly stressing the plants to toughen them up and yield sturdier stems. Seems to work as far as I’ve observed, and it does no harm.
The third theory, which isn’t really a theory, is that you don’t want to over-fertilize. I use half-strength fish emulsion and liquid seaweed, applied just a couple of times during the indoor life of the plant. Over-fertilization causes rapid growth and leads to leggy plants.
The next theory is that my grow closet is too warm. I believe that greenhouse-grown seedlings grow stockier partly because they’re grown in cooler temperatures. Yes, even the tomatoes and peppers. I haven’t found a way to cool my small space other than the little fan, so I live with it in the mid-70s. I suspect that the mid-60s would be better for the seedlings, but it is what it is.
And finally another theory that I’m not sure about: moisture. It seems obvious that seedlings shouldn’t be kept either too wet or too dry. But I suspect that erring on the side of dryness is better than the other way. Again, just a little bit of a challenge to help the plant accustom itself to real life.
I’d love to hear your thoughts on any of these ideas, because nothing teaches like first-hand experience.