blomma wrote: Pfg,
I started using it mid-April. However, there are no tender plants in there. Iris and Daylilies are all hardy. I wouldn't have put tomatoes in there that early.
Your idea of a heating mat is good. I thought of but didn't think I needed. Mine is not freestanding. It is up against my garden shed due to the high wind we get here.It faces east so screened from western sun.
Below is a photo of what I used 2 years ago. It worked nice also but it is too low for me due to back problem. Bought that one from Parks seed co.