North Westford rises in long apple-country hills, orchard rows on one side of the road and hayfield on the other, the whole of it tilting toward the Merrimack. Merrimack Properties tends lawns across those slopes, where a mower has to hold its line on a grade and the trimmer finishes what the deck can't reach. Fall cleanup here is a serious stretch of work, because the leaves come down all at once the week the wind turns cold. After that the plows go on: driveways cut open, turnarounds widened, front walks shoveled clear. The hills make all of it harder, which is most of the reason it's worth doing right.