Hey all, I just want to be clear that I’m not telling anyone not to dome their seedlings if it works for them, just explaining why I choose not to. I know it’s a very common practice, and lot’s of people here suggest it.
The benefit of doming is that you’re making sure there’s enough moisture in the air around the seedling, but in my opinion it’s fairly easy to just use a humidifier and keep the grow space at a proper relative humidity. I keep a wet sandwich baggie over my solo cups while I’m waiting for my seeds to sprout, but I remove them as soon as a seedling breaks the surface. In my opinion, at this point the new seedlings benefit a lot by having a gentle breeze blowing on them. I can’t think of why I’d want my seedlings to be sitting in stagnant non moving air when they can be starting to develop strength in their stems from day one instead.
I also think that there has been a melding of advice over the years between seedlings and cuttings. A cutting or a clone absolutely needs to be domed or in a germination chamber because it has no roots at all, it’s just a stem stuck in a substrate, and it takes time for roots to even start to grow. Drawing in moisture through it’s leaves is a cuttings only means of obtaining water. That is not the case with a seedling. Sure, it doesn’t have an established root system on day one, but it does have a tap root, and it works it way down through the medium a lot faster than many would give it credit for. I’ve literally seen roots at the drainage holes in my solo cups on day 3 above ground.
Again, just my opinion, but any number of days that a seedling is sitting under a dome, it’s missing out on the strengthening effects of a gentle breeze. Might not be a big deal with photos because of the extra time, but if you’re growing autos, every day means a lot, and my seedlings always get off to great start without the need for doming.
Your opinion counts and agree Grow Bro, I dome my seedlings when I have several grows in different stages and the lung room temps and RH set for those around 45-55% and the seedlings needing higher temps and RH…of course their in a different tent to make both environments easier to manage 
Can’t disagree with any of that.
I rarely dome past germination…
personally i have had far more issues when humidity is high vs. low at any stage of my grows.
I’ll dome, but only when i have to…like Jan-Mar when RH bottoms out.
Ive done both and still dome, and alot more than in the beginning, but i agree with you there. I think gentle breezes are a big part of making plants strong.
I agree, only use a dome when when the humidity is lower than 55%. When I started using large domes, and use able to but a humidity sensor under it. This was a real eye opener, as the humidity was much higher than I assumed.
Another good rule of thumb is the amount of moisture that collects on the inside of the dome. If it is collecting larger drops of water the humidity is probably too high. You want it to only collect no more than a little fog on the inside.
Yep if using a hard dome i like to use spacers underneath to allow some air exchange, or you can do kind of the same using ziplock bags