Depends on which ones. For the impatiens I covered, not really. They are so short and small right now that they won’t be injured by breaking the stems.
The mattress pads are polyester and light enough when spread out. The other things I used were old sheets doubled over, cardboard, straw, all depending on what I was covering.
With the conditions, the ground is still pretty warm. The frost is going to be due to evaporative cooling because of the clear skies and light winds. Covering them with almost anything will help hold in some ground heat and prevent the evaporative cooling.
In my flower garden I have tulips, some perennials, dahlias, salvia (sp), cosmos and assylium (sp), a baby scotch pine, and a small maple tree.
Hubby stuck 3’ height stakes all around it, and draped an old tarp over it all. It was still open a bit at the bottom, but it seemed to work.
;-)