By mid-November the oaks around Somerville have let go, and every lawn in town lies under three inches of brown. RG Tree Service works those weeks hard: leaves cleared, beds raked out, grass given its final cuts before the ground goes hard. Earlier in the year the job is the steady one — mowing on a schedule, trimming the tight spots, edging where turf wants to creep over the walk. Leaves left to sit will smother a lawn by February; taken up in time they cost the yard nothing. Come April the same grass comes back thick, and that is the whole point of autumn.