April announces itself in Hempstead as a sound before it is ever a sight: trailer gates coming down on a side street while the early trains pull out of the terminal a few blocks over. LawnMan Service opens the season right there and holds the line all summer — weekly mowing, string trimming along fences and foundations, edging to the sidewalk, spring and fall cleanups carted off. Light on this stretch of Long Island comes late and stays long, so there is room to finish a block without hurrying any part of it. What the crew is after is the way a yard looks at seven in the evening: stripes still standing, clippings blown off the concrete, the curb line swept. Lawns in Hempstead and the neighborhoods that run straight into it.