Well, our makeshift seedling heat mat worked perfectly. It stayed consistently warm without ever overheating, and just about all of the seeds sprouted within a week. Pretty good, especially for peppers, which can be very difficult to germinate.
And then after that nothing happened. Our little seedlings stayed pretty much the same size for weeks. I couldn’t figure out what the problem was, until it dawned on me. The growing medium I had used was no good. Last year I started a lot of my seeds in coconut coir. They got off to a slow start too, but they did fine once they had been transplanted, so I didn’t give it much thought. This year I started my first couple rounds of seeds in an organic seed starting soil mix and they did great. But then I ran out of it, so I decided to just use the coconut coir I had leftover from last year for the tomatoes and peppers.
I don’t know why it took me so long to figure this out, but I finally realized that the reason the tomatoes and peppers weren’t growing was that the coconut coir doesn’t provide any nutrients. So last week I repotted everything in slightly larger containers with some really good organic potting soil. Within a day they were noticeably bigger. It was pretty amazing.
I moved these seedlings to the cold frame a couple weeks ago, but since then the maple trees in my yard have gotten their leaves, so the cold frame was suddenly only getting afternoon sun. On top of that we had some cool rainy weather, and the spot where the cold frame just wasn’t drying out. The seedlings needed a warmer, sunnier home quick. So Friday we moved the cold frame over to the community garden. We dug out a little sloped trench and set the cold frame in it to maximize the sun exposure inside.
My seedlings seem quite happy in there now, and they are really starting to grow. They are still pretty tiny, but they’ll catch up quick. I just keep reminding myself of what one of my garden neighbors said last spring when it was cold and rainy and everything was getting off to a slow start– eventually everything catches up.
forgottenpickles.com 
I’m glad you realized the problem quick enough. Sometimes it’s just the simplest of things. Our peas didn’t come up very well (my husband soaks the seeds and then plants directly in ground) a few weeks ago – probably 50 percent sprouted. Then my husband figured out what he did wrong – he used mushroom manure directly on the seeds and it was too strong. He planted new seeds w/o manure this past weekend and hopefully that did the trick. Happy gardening!
A lot of my peas didn’t come up either, and I can’t even blame it on manure! I hope your second round does better!
I had a very similar experience with my Ground Cherries and Wonderberries. As soon as I put them in the bed I had lasagna composted over the winter, they really took off. They just weren’t getting enough of the good stuff in the starter medium. I’m glad to see yours are doing well.
It’s amazing what a difference some good soil can make!
I’m with your garden neighbour, I’m sure everything does catch up. I’m behind this year on all my sowings but then I think about it a bit more carefully and I realise that I wouldn’t be planting much out yet anyway. Hope you have a great week and I’m pleased you found and fixed the problem :)
It’s true! Those tomato plants have grown so much in the past week you’d hardly believe they’re the same little scrawny plants. I think I worry to much about getting everything started as early as possible. I need to relax!