Lyn - Try having 2-3 weeks of -15 to 20 deg weather every single January, not including windchill. Trust me, it's winterkill, not canker. Even Austrian Copper, who has NO mulch, has winterkill and that's supposed to be one of the hardiest roses for my area. The wild roses that grow native to CO die to the ground every year as well, so my situation isn't unusual. I usually use Western cedar for mulch if I can afford it, but getting 30 cubic yards at $41/CY is pretty expensive.
