I didn't believe it, but it's true. Beautiful (and actively growing) salad greens of all kinds in mid-December. Yeah, OK, this isn't exactly Minnesota, but still I'm impressed. So what's a hot bed? In late August, I dug out a bed down two feet, filled 1/2 full with horse manure, then 4 inches of sand, then filled to surface level with composted top soil. I then constructed a cold frame over the top and seeded. The manure is decomposing and warming the soil, and with the protection and help of the cold frame, I'm getting temps up to 70 degrees F inside, even when it's freezing out. Neat, huh?