Whenever we get some as gifts for Easter,,, After they pass blooming, I bury them in flower garden. They keep coming up year after year. I have different varieties of lilies. I'm in Zone 5A. The new zoning chart says we are in 6. I still disagree with them. :idunno
I'm pretty sure such what you made is called a "COLD FRAME" ,, Yes, it works like a green house. :thumbsup
Long ago, my Mom used to set those up in her garden as an early start. She started out with window panes that were extra around the house. (from replacement storm windows), Then...
Since you are gardening,,, it would be good to post your location. It is much easier to give advice based on climate. If you want to be less specific about your location, then just post your zone.
WISHING YOU BEST,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, :highfive: