The mini-greenhouses, or cold frames, have been working out extremely well as seen by the healthy tomato plants now growing inside!
The tomato seedlings had been sitting in the greenhouse in their soil blocks waiting to be planted in the garden. I wasn't able to transplant them earlier because the weather wasn't cooperating, but they seemed to be holding up just fine. I was getting concerned because some of the plants were starting to flower early, but as you can see from the photo the soil blocks allowed the roots to grow thick without becoming pot bound and the plants were healthy despite their longer stay in the greenhouse
I previously had kale growing in the min-greenhouse which I planted last fall. I harvested everything, gently cultivated the soil and topped with 6" of homemade compost before planting the tomato seedlings. The mini-greenhouse has been working well, keeping in the heat and moisture during the colder nights and days, as seen by the condensation on the plastic. I am careful to monitor the temperatures so it doesn't get too hot inside. During the warmer sunny days I open the roof vents for ventilation and to allow the bees get inside to do their job.