5-10 Grass clippings hold water in and keep weeds out Published May 4, 2011 at 800 × 600 in Gardening Made Easy – For Moderate to Arid Climates ← Previous / Next → Mulch In Plots Holds a Lot of Moisture Just as grass clippings keep weeds from springing up by blocking out light, the ground covering mulch also shields moisture-rich soil from excess water evaporation.