The first warm Saturday in April is the drop of the flag around here — every garage along Mound Road opens at once and the whole city smells like two-stroke and thawed dirt. GREEN FLAG LANDSCAPING LLC is already out ahead of it. From that first cut through the last leaf haul the work is mowing, trimming, edging and cleanup; from the first clipper through the March thaw it is plowing driveways, clearing walks and spreading salt. Sterling Heights streets run straight and long, which means a lot of frontage and a lot of edge, and edge is where a lawn either looks finished or does not. Two seasons, the same habit: leave a place sharper than you found it.