Contrary to popular belief, tin cans protect seedlings only from winds. They do not protect from cold. For cold protection for seedlings planted early, remove the lid and cut off the bottom of a plastic milk jug and place over the plant. Remove in mid-May.
—Barbara Rusk, Ames Garden Club
Gardening in Iowa and Surrounding Areas, by Veronica Lorson Fowler with the Federated Garden Clubs of Iowa