Nickajack Creek runs under the Concord Covered Bridge with a sound you can hear before you see it, and in March the banks green up a full two weeks ahead of the lawns on the ridge. Burns Lawn Care LLC starts its year about then — the first mow of the season, beds cut back and re-edged, winter debris raked out of the corners where it drifted. Through the growing months the routine holds: mowing, trimming, edging, blowing clean, shrubs kept in shape so the front of the house has a line to it. When the oaks let go in late fall the leaves come off in one sweep rather than a dozen half-tries. A crisp edge along a Marietta driveway is a small pleasure, and it is the one this crew chases.