Where Fort Collins runs up against the first ridges, the soil turns thin and rocky and the grass has to be persuaded rather than commanded. DEVIL'S DEN OUTDOOR SERVICES LLC mows and trims those yards through the hot stretch of August, cutting high enough to hold moisture, edging where lawn meets gravel and stone, clearing the dry litter that stacks up along fences. Afternoons out here build thunderheads over the hogback that mostly slide past without giving anything up. Then evening comes, heat lifts off the rock, and a lawn that was cut right that morning is still standing up straight. Along the foothills edge, that counts for something.