Westland's soil is heavy clay, pressed down first by glaciers and then by subdivisions, and grass that thrives on it has to be coaxed rather than commanded. ExperiGreen & Top Lawn works with that ground, mowing, edging and tending lawns through the long green stretch from late May into autumn. Under the big silver maples and pin oaks that shade these streets, turf goes thin and uneven unless somebody is paying attention to it. There's a genuine satisfaction in watching a patchy yard fill back in and hold its color into September. Green, evenly, corner to corner, is the whole aim.