By bagging and getting rid of your grass clippings you are throwing away free fertilizer. Grass clippings contain many nutrients that when used by the soil enhances the lawn's ability to fight disease, insects and drought. Generally speaking with weekly mowing, a 1,000 square foot area will generate approximately 2 pounds of nitrogen from the clippings per year. By using a mulching mower you even decrease the size of the clippings making them even less noticeable. If you leave the grass too long and then cut, you create large areas where the clippings are too thick to be utilized by the lawn. These clippings should be raked up as summer heat can cause a greenhouse effect underneath and cause damage to the lawn. By mowing 1-2 times a week at a height of 2 1/2 to 3 inches with a sharp mower blade, the clippings will begin to break down very quickly. Usually within a week the plant will utilize the nitrogen from these clippings and encourage new growth.