Plenty of side streets run beneath an old arch of shade, and by September that canopy starts letting go a little at a time. Jimmie G's Lawn and Tree Service works the grass underneath it — mowing through the thinning light, trimming where roots and trunks make a mower useless, clearing the yard so the lawn isn't smothered as fall comes on. Grass under mature trees is a negotiation, and it rewards a lighter hand and a sharper edge. The last hour of a September afternoon is the right time to stand out at the sidewalk and look back at a yard that's crisp all the way to the fence. The season turns; the lawns go on looking tended.