I said the lettuce was hardy to about 10 degrees, especially with a good snow cover. It turns out it is reasonably hardy at 1 degree, with just an inch or two of snow! These were in an unprotected garden. Some of the outside leaves will probably die on the plants that were planted on Sunday, but it looks like the plant will grow back. I'll be checking in on these to see. I hope all the plants that were planted in Boulder fared well, too. The extra snow in Boulder should have helped insulate the plants.