As we move more deeply into the lawn-mowing season, I can’t help but cringe when I watch landscapers and homeowners attack their patches of green.

First, most of us cut our lawns too short. And then we water at the wrong times. If we could manage to correct these two lawn-maintenance flaws, we’d have healthier lawns, and we'd take a step toward being "greener" because we'd use smaller amounts of fertilizer and chemicals.

Let’s start with mowing height. While mowing height largely depends on the type of grass you have, it’s safe to say you should consider two heights. In the spring and wetter seasons, the most common of turfgrasses — specifically bluegrass, rye and fescue — should be cut at about 2 to 2.5 inches high. Later in the summer, starting at about the end of June, or when the season is hotter and drier, those more...