Starting seeds in a hoop house cold frame is like putting a greenhouse on your vegetable bed. The hoop house warms the soil and then you drop seeds right into the soil. No transplanting or grow lights, no transplant shock. This is our cheap PVC hoop house that can be made with salvaged or recycled materials, and then you can grow vegetables in the hoop house. What I love is how the cold frame warms the soil to 15F above the ambient soil temperature.
Plants that do well for seed starting in a hoop house are those that are cold tolerant. What the cold frame offers is a warmer soil and air temperature, which aids in germination. Yes, peas can be planted in snow, but they germinate much better in slightly warmer soil, same for lettuces and cabbages like kale, just a bit warmer and they sprout better. For this video I put sugar snap pea seeds in and radish seeds. Radishes are one of those seeds that are kinda fail-safe, so you feel ok even if some of the other plants didn’t take as well.
We have several videos on how to build a hoop house cold frame and how to use a plastic greenhouse like this, here is the video of us building our first cheap hoop house. I think its key to have the thermally controlled vent, if it gets too hot, you might consider putting a vent on each end of the hoop house. The PVC we use in this cold frame could be salvaged or recycled from another project or job site. The plastic we use is 3 mil plastic from the hardware store. With care this plastic will last several years. In the middle of summer, I hang my hoop house on the back side of the woodshed, and the plastic stays in good shape for a few years.