Lawnmowers can leave uncut blades of grass for a variety of reasons, such as: (1) the grass is wet from watering or dew, (2) the blade is dull, nicked, out of balance, or improperly installed, (3) the user is trying to cut very long grass down to a short level in one cut, (4) the user is walking too fast, or (5) the underside of the deck is clogged with previously cut grass, mud, or other debris. For best cutting results, keep the blade sharp and well balanced (see instruction manual), and keep the deck clean. When cutting long grass, it is best to cut slowly or to cut to a middle length first and then re-cut to the final length. For optimum cut quality and lawn health when mulching, never cut more than 1/3 the length of the grass at one time and preferably never cut more than 1-1/2" .