Most people who are particular about the appearance of their lawns remove the clippings when the grass is cut. In some cases it is a good idea but in many others it is pure waste.
The clippings of zoysia, Bermuda and St. Augustine almost always should be removed. They decay slowly and when they accumulate thatch develops.
It is different with cool-season grasses such as Kentucky bluegrass, fescue and rye. If the grass is rather thin and the clippings can filter down to the soil surface, they decay speedily. As they decay, considerable nitrogen, phosphorus and potash are returned to the soil. They analyze roughly at between 5-2-4 and 6-2-3 (nitrogen-phosphoruspotash), according to specialists.
But if the grass is rather thick and the clippings cannot get down to the soil level where bacteria will break them down, they may accumulate and smother the grass.
If used for making compost, the clippings should be mixed with tree leaves or some similar material, according to Admiral Neill Phillips, president of the American Boxwood Society. Otherwise, when they dry out they pack together and it takes a long time for them to start decomposing.
"In summer when we have lots of grass clippings and not many leaves to mix with them," he says, "we pile the grass clippings into a separate heap.
"These dry, unrotted grass clippings are invaluable for weed control. Spread two to three inches deep around shrubs or bushes, they cut off the encroachment of choking grasses and weeds almost completely.
"For flower beds the mulch of grass clippings is absolutely invaluable. In June as soon as the annuals have been bedded out, all the flower beds are mulched with two-inch thickness of dry grass clippings.
"Watering and weeding are then hardly needed for the rest of the season. No material is as excellent as grass clippings for conserving ground moisture and for resisting weeds.
This mulch should be used only around established plantings. No bedding plants (as well as no weeds) can sprout through it.
"After the first freeze in late autumn has finished off the growth of weeds, the grass-clipping mulch is raked off. It will still show little decompostition.
"A heavy mulch of shredded composts is then applied to the beds for protection against winter heaving due to alternate freezing and thawing.
"This shredded compost decomposes rapidly in the spring and provides nutrients for the plants growing there."