Behind the triple-deckers near Savin Hill the yards are barely bigger than a rug, and every one of them still wants mowing, trimming and a clean edge come September. A&M Home Services LLC works those small Boston lots — the strip beside the drive, the patch behind the porch, the sunny corner that grows twice as fast as everything around it. Grass this close to the water stays green late, so the season runs long and the cuts keep coming well into fall. Leaves get gathered before the first hard rain packs them flat against the turf. Small ground, handled properly, changes the feel of an entire street.