There is a week in April when the slopes of Nichols Arboretum turn a green so new it looks lit from underneath, and every lawn in Ann Arbor tries to follow. Spring Green is a lawn care business built around that stretch and the six months behind it: mowing, string trimming, edging along walks and drives, and cleanups that clear the winter litter first so the season starts on open ground. Summers here run humid and green-hungry, and the mowing rarely lets up until the maples turn along the river. Then the fall cleanup puts a yard away — leaves off, beds cleared, the last cut low and level. A kept lawn is a small promise a house makes to its street.