My son Dylan gifted me with a small greenhouse last Christmas. It has four shelves and has a well-fitting plastic cover.
I usually keep my plants on the windowsill until they are ready to set outside. They end up being lanky and thin, because they are reaching for the sun. But in the greenhouse, they get so much more light. They are stocky, with thick, strong stems, very green and healthy.
In May, I bought two rhodos full of flowers. I set them in the greenhouse to protect them from the cold. On May 20, I saw a hummingbird hover near the plastic, looking longingly at that nectar source. Of course I took the rhodos out immediately! A few minutes later, the hummer had a drink of nectar.
On warm days, the greenhouse develops its own misty atmosphere.
When the weather threatens to get too close to 5 C, I drape the greenhouse with white row cover to insulate it from the cold. This is much easier than lugging all the plants back into the house. And light passes through, so I can leave it on during the day if it is too cold.
The marigolds, zinnias, three kinds of tomatoes, peppers, zucchini, purple basil, coriander, lettuce, and ice plant and geranium cuttings protected in my tiny greenhouse are all doing very well.
some healthy looking lettuce