The first mow of April in Billerica smells like mud and new grass at the same time, and every lawn on the north side of town is a week overdue at once. Exterior Essentials starts there, clearing what the winter left, taking that first cut, trimming and edging back to a clean line, then holding the yard steady all the way to the fall cleanup. Around the ball fields and the neighborhoods off the main roads, the ground stays soft into May, so early cuts get taken light and the turf is allowed to catch up. There is something plainly good about the transformation of a matted spring yard into a level green one over a couple of visits. That is the whole point of the work, and it shows from the sidewalk.