This plastic tunnel is being used inside of the greenhouse to protect tender plants against a late hard freeze - very effectively I might add.

A simple plastic tunnel like this can serve as a cold frame to grow salad greens  all winter long, to grow out tomatoes and other tender plants, to extend the season for an early Spring start or a late Fall harvest, or even as a screen house to keep birds off of your strawberries or vine borer moths off of your squashes.  You can also use one of these to dry out water logged beds and warm up the soil so that you can begin planting  in early Spring. These devices are so useful, cheap, easy, and quick to build that everyone should have at least one – it’s almost as good as having your own polytunnel greenhouse. » Read more: Simple Plastic Tunnel Cold Frame or Row Cover