At the east end of the city the Nashua River finally meets the Merrimack, and the ground down there is flat, sandy and quick to green up. Luke's Landscaping LLC mows through that neighborhood and the ones above it — cutting on schedule, trimming the fence lines, edging drives and walkways, then clearing the yard right down to grass each spring and fall. River-bottom lawns come on early and hold on late, which stretches the season at both ends. The routes run Nashua and over into Hudson, Litchfield, Merrimack and Pelham. Nothing complicated about the idea: show up, cut it right, leave the pavement clean.