I'm an avid gardener, and see so many things on the stores shelves to protect young plants in the spring from cold weather if you want to get a jump on the season. Some of them you fill with water and it insulates the plants from the cold. They can cost easily up to or even over $10 each. A complete waste of money, IMO. I save gallon plastic milk jugs. I cut the bottom out and place them over the young crops to protect them. It's like a mini cold frame for each plant. Cost $0. Reward, more and earlier produce from my garden.
These work well but I don't usually drink enough milk to have a supply of them. I just use a clear plastic drop sheet laid over a bunch of sticks and held down with stones on the edges. This works well for rows of seedlings. If I am able to do so, I remove the cover during the day when it is warm enough for the seedlings. Another technique for tomatoes is to use a clear plastic garbage bag over top of the tomato cages if you have them. The cages provide the frame while the plants are young and when they are too big for the little greenhouse, it should be warm enough to remove the bags.
I've used the plastic packaging from sheets and comforters to keep my plant moist prior to becoming seedlings with true leaves. It's not an attractive look but it serves it's purpose. I once used a aquarium as a greenhouse too. Reduce, reuse and recycle.
