No, you don't need compost starter. Just greens and browns, a little water, flip to aerate occasionally, etc. And 40° isn't a magic number, just something off the top of my head that I thought you (not the compost) might find tolerable. My compost is out there all winter, often in subzero temps. It just doesn't break down much then, resumes when temps start to rise and I actually tend it.
Composting tutorial
http://sarasota.ifas.ufl.edu/c...
Karen
