On a January night the lights of the Nashoba Valley slope glow over the treetops, and half of Westford can tell how the snow is going by them. Bear Hill Landscaping is reading the same weather from the seat of a plow truck — driveways opened, walks shoveled to the door, salt and sand across the steep spots this hilly town has in abundance. When it lets go in spring the work turns green: cleanups, weekly mowing, trimming, edging, mulch laid into the beds. Westford's yards sit among stone walls and old orchard ground, which makes for beautiful lawns and awkward corners. Both get done.