In December the tule fog rises off the Tuolumne River and spreads over Modesto so thickly that streetlights glow like lanterns late into the morning and the cottonwoods along the water vanish into white. It is the valley's hushed season, when grass grows slowly and a yard is less about growth than upkeep: leaves raked, borders kept tidy, the lawn cut when it asks for it. Sustainable Greens is a Modesto lawn care business, and the payoff of attentive care shows clearest in months like these, when a tended yard stands out against the gray. Then February brings the first mild afternoons, and the grass stirs and thickens, ready to be shaped again. When the fog finally lifts for good, the lawn is already in trim and waiting for spring.