If you mow your own lawn make sure you are keeping those blades sharp on the mower. Here at Aspen we sharpen every night, it has happened that we change out blades half-way through the day to insure a good clean cut. Here is a picture that might help you determine if you need your blade or blades sharpened.
Leaf blade A shows what a leaf blade should look like after mowing. Leaf blade B shows a leaf blade injured by a dull mower blade. Leaf blade C indicates that the mower blade is not sharp enough. The white tissue sticking out of the leaf blades (C and D) is plant vascular tissue. Leaf blade D was repeatedly mown with a dull mower blade.