By late June the Rahway River bottomland turns Clark a deep, humid green, and the lawns above it grow faster than anyone can quite keep up with. Emerald Lawn Sprinklers works that push — mowing on a tight weekly line, edging walks and drives, trimming around trees and beds, and handling the cleanups that open the season and close it out. Union County ground here is heavy and holds water, so a lawn cut at the right height in the right week stays even instead of scalping in the August heat. Long summer evenings make the striped rows worth stopping to look at from the curb. A yard that holds uniform from June clear through September is the whole ambition.