Yards are thirsty. On average, American homeowners spray more than a quarter of the water they use in a year over their grass and gardens — a figure that rises in the summer, especially in hot, dry areas. Grass is the biggest water hog, gardeners say. … In dry regions, overwatering can drain dwindling drinking supplies and the bank accounts of homeowners stuck with big water bills. … Many homeowners could be smarter about the way they use water, according to professional gardeners, who recount with dread tales of sprinklers spraying sidewalks and wall-to-wall lawns blanketing suburbs in arid areas where lush lawn grass would never naturally grow. They shared tips on watering smarter and planning landscapes that need less irrigation.