Annual call for indoor seed-starting advice - mastering watering?

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Happy (almost) Easter everyone!
I feel the need to check in with you all every Spring for your helpful advice on indoor seed-starting.
I think I am getting better (I added a heat mat one year, upgraded to Agrobrite T5 grow lights the next year, tried better seed-starting media another year, etc.), but I still struggle a bit and have moments when I feel like all my fragile seedlings are about to die.
Mastering WATERING is still challenging.
I start mostly pepper and tomato seedlings indoors, with pepper seeds started this year around four weeks ago and the tomato seeds about three weeks ago.
As I have mentioned in past years, my seed-starting setup is located in my unfinished basement, with overnight temperature dipping down into the 50s. Your previous feedback to this reality has been to keep the heat mat on continuously, even after initial sprouting.
My idea this Spring was to try and set up a DIY “greenhouse” to try and keep a more consistent, warm and humid environment.
Trying to both save money and honor calls for social-distancing in this strange time of COVID-19, I re-purposed 2x existing large translucent plastic containers with lids that I had lying around:
IMG_5954.JPG

That seemed like it worked well for the initial germination. (If anything I was worried that keeping the lids on was making it too humid.)
Once the seedlings emerged, however, I began to worry that the grow lights were too far away from the seedlings. The plastic containers are a good 12+ inches high, and I know most people seem to recommend keeping grow lights only a few inches above the seedlings.
So I wound up rethinking my design and found a larger but shorter plastic container, and now the grow lights are much closer to the seedlings, probably 4 inches or so:
IMG_5994.JPG

Once again I am struggling with watering, as things seems to go VERY QUICKLY from seeming to be too wet to too dry. The image above shows both the look of the point of dryness I have typically been waiting for before watering, as well as what they look like after I water them.
And here are a photo of a couple of the pepper seedlings looking less-than-perfect, taken two days ago (4/9):
IMG_5991.JPG

IMG_5993.JPG

I am still struggling in trying to fine tune heat (should I still keep the heat mat on 24/7?), light and water.
I know that bottom-watering is recommended, but the large plastic bins I am using have no drainage holes themselves so it’s not really convenient to water them from below, as I would have to remove several dozen peat pots with seedlings in them to drain out the excess water from the large container they’re sitting in.
Thanks for any helpful advice anyone has.
Stay safe,
-=RR=-
New Haven, CT
Zone 7a
 
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Your watering does look a bit off. Have you tried putting your growing medium into another identical pot without a seed and use it as a gauge? Maybe even two or three of them.
 
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Hi Chuck. Thanks for your response. What will I try to test/replicate with the additional pot(s): how quickly they dry out? Also, any general "best practice" advice for setting up a more consistent watering regiment given my current setup and location? (I'm already wondering if I should invest in some sort of capillary mat setup for NEXT year...)
 
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I find that the pressed pots like that are very difficult to regulate moisture, which is why I no longer use them. Sorry I can't help.
 
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Hi Chuck. Thanks for your response. What will I try to test/replicate with the additional pot(s): how quickly they dry out? Also, any general "best practice" advice for setting up a more consistent watering regiment given my current setup and location? (I'm already wondering if I should invest in some sort of capillary mat setup for NEXT year...)
Because I live in a place with mild winters and an early planting season I don't need to go to all the trouble you do to grow seedlings. I will tell you how I do it and maybe you can incorporate into your methods. What I do is use plastic containers. I have found that the peat/coir/manure containers allow moisture to escape by osmosis through the sides of the container. And this makes it just about impossible to maintain a correct moisture content. So, I fill the plastic containers about 3/4 full of medium. I use 1/2 and 1/2 sterilized garden soil and my sterilized homemade compost. I then saturate the medium, let it drain and place my seed on top. I pat the seed down to make good soil contact and then sprinkle dry medium on top to the correct depth. I then cover the containers with Saran Wrap. Watering isn't necessary until after seeds have sprouted. I then place the sprouted seeds and containers into a fairly tall casserole pan and when I water I pour water into the pan, not onto the seedlings. I also maintain a temperature of about 80F with a heat mat. You can replicate this. Just don't use those pots. In fact you could improve my system by having different heights of containers into which you place your seedlings and place Saran Wrap on the top and still use your lighting system thereby making a miniature terrarium and to water even less.
 
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Thanks @Chuck for the helpful feedback.
Also thanks @posipurrs for contributing to the conversation. What setup do you use?
I have heard good things about the soil block method and a wondering if that is also worth considering.
 
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Thanks @Chuck for the helpful feedback.
Also thanks @posipurrs for contributing to the conversation. What setup do you use?
I have heard good things about the soil block method and a wondering if that is also worth considering.
I tried soil blocking. It will work when you find the correct mix for your soil but the watering issue is worse than with the bocks than with peat containers because you can't measure the moisture content correctly without the compressed soil coming apart. The block makers are not cheap either. I sold mine on Ebay. In all fairness, I guess that if you found the correct mix in commercial products all would be well, but, I'm too cheap to be buying compost and garden soil when I have my own for free. The only thing is that my homemade compost and garden soil doesn't compress very well at all.
 
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Don't use a dome if you want to have success. If you keep the top on, after the seeds spout, they will die. Also having a light source closer to the seedlings or sprouts will help you dry the top of the soil and help your plant grow faster. You can take them off the heating mat during the day. Domes are good to maintaining high humidity during germination in super day areas only. After the seed sprouts and has grown leaves, a high humidity will cause the cell tissue to suffocate from the excess amount of moisture through the stomata. Also, you may want remember to always do a water test on one plant first, to make sure its good before watering everything. That way you won't kill everything at once.
 

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