A few days ago, my planting trays were under a sheet of plastic wrap to help keep temps and humidity up. That's phase one and it's a very short phase. It stops as soon as the seedlings emerge. As soon as the first seedling emerges, the plastic wrap comes off. Failure to remove high humidity domes or plastic wrap once a seedling up, is the perfect way to invite damping off. Damping off is any number of fungal diseases that cause your seedlings to essentially rot at, or near the soil line. It's heartbreaking when it happens and there is no cure for it. The way to prevent it is to keep your humidity down and keep air flowing around your plants. I have my ceiling fan on high to help with air flow.
My phase two set up focuses on maximizing light exposure. I use high output, low temperature grow lights. The low temperature allows me to place them within a few inches of my seedlings. This helps prevent stretch. Stretch is when seedlings grow too tall too fast and are weak as a result. Short stocky seedlings are better than tall gangly ones. They are much less likely to be damaged on transplant. Since my seedlings are in a southern exposure in February in zone 5, they won't get enough light from the big window to prevent stretch. They need about 16 hours of good light. The grow lights make a big difference. I enhance the light they receive by covering cardboard squares and angling them around the seedling trays to help bounce light around. Once temps rise, though, the foil goes away in order to prevent the crispies.
My seed germination is going very well. Every tomato type has already germinated with the exception of Amerikansky Sladsky. Among the peppers there is at least one plant up of each type with the exception of Sweet Chocolate (older seed) and Fat and Sassy (the hybrid). It's interesting that the so called very early pepper hybrid is lagging behind the heirlooms so much. It is the farthest from the heating vent, so perhaps that degree or two makes the difference. One would think an early variety would have less heat needs though.
Notes on the seedlings this week: San Marzano seedlings from both BI and Pagano nurseries all required rescue from their seed casings. (Annoying!). Brave General is a very small seedling and doesn't match its name. One of the Striped Roman seedlings has three leaves. Black Cherry is this week's leader with respect to growth and health. No sign of a single leek so far. I need to read up on that. I can't remember what they need for germination.
I was going to start assembling the cold frame this week but in reviewing last year's notes, it was the first two weeks of March that gave me the biggest headaches with respect to big storms and temperature extremes. I think I'll hold off a bit more. Meanwhile, I need to plot how to make assembly an easier task than hauling all those bricks to the patio.