The Mill River widens into Lake Whitney at Hamden's southern edge, and the streets running down to it hold their humidity long into a summer evening. D & L Landscaping and Design LLC keeps those yards in shape — mowing, string trimming, edging, and carrying the season's debris away — then turns the trucks around in December for plowing, walk clearing and salting. There is a moment at dusk when a freshly cut lawn goes deep green and the borders look drawn with a straightedge; that is the target on every visit. In January the target is simpler and just as satisfying: a drive open and clear before the first car needs it. Hamden, both halves of the year.