Don't bag your grass clippings

By Melanie Mathieson
Gardening Guru

Yard waste, such as grass clippings, leaves and branches, should be composted and not sent to the landfill unless your landfill has a separate composting section. Any seasoned gardener knows that these materials are a valuable landscape resource when composted or used as a mulch. Grass clippings do not need to be collected from the lawn after mowing, as they actually benefit the turf by returning nutrients and organic matter to the soil. Below are some frequently asked questions that I often get from homeowners about taking care of their lawn and what to do with all of those clippings. I hope that this column can dispel the myths and clear the picture for you and you start to recycle those grass clippings the environmentally friendly way – right back into the lawn.
What benefits do grass clippings provide if returned to the lawn?
Grass clippings returned to the lawn provide up to 25 percent of your lawn’s total fertilizer needs. Clippings contain about 4 percent nitrogen, 2 percent potassium and 1 percent phosphorus. While decomposing, they also serve indirectly as a food source for the bacteria in the soil, which are doing many beneficial things (such as decomposing thatch) for a healthy turf environment.
How should I mow my grass if I want to the lawn to benefit from the clippings?
Grass should be mowed and left tall (at least 2.5 inches) and clippings should be returned to the lawn to produce a healthy lawn. Set your mower at a tall setting so clippings easily fall into the lawn. When it is cool in the spring and the fall set your mower at 2 1/2 to 3 1/2 inches, and during the hot summer months, use a setting from 1 1/2 to 2 1/2 inches. Mow frequently so you remove no more than one-third (about 1 inch) of the total plant height. This is important because you do not want the grass to get too long between mowing so it looks like rows of hay in your yard when you are finished. Several studies have shown that it takes 30 to 38 percent less overall time to mow often and leave the clippings than to mow weekly and bag the clippings. Who wouldn’t want to cut their workload back by at least one third?
Do my mowing practices need to be changed to follow the “don’t bag it” plan?
Regular mowing with a sharp blade is essential for reducing the need to collect clippings. Grass must be mowed often enough so that no more than a third (about 1 inch) of the vertical grass height is removed with each cutting. “Don’t bag it” does not mean you should leave an excessive amount of clippings piled on the lawn surface after you mow. Leaving too many clippings will damage the lawn. Returning clippings to the lawn usually means having to mow more than once a week during the few weeks of rapid growth during the spring and early summer. Mowing more frequently is not as much work as it may appear, because lawns mowed at the proper height cut more easily and quickly. As lawn growth slows in the summer, grass can be mowed less often.
Why recommend taller mowing heights?
When you set your mower at a higher cutting height, the grass plant produces a deep and efficient root system that can reduce the need for watering. Taller mowing also helps to “shade out” many weeds. Simply remember to set your mower at a tall setting so clippings fall easily into the lawn. When grass is mowed closer to the ground it has fewer roots and uses water inefficiently. Grass that is mowed higher, has a more extensive root system and is more drought resistant.
Do clippings returned to the lawn contribute to thatch problems?
Thatch is a layer of undecomposed or partially decomposed grass roots, stems, crowns, runners and lower shoots that accumulate between the soil surface and actively growing turf. Grass clippings contain 80 to 85 percent water and decompose much more quickly than other grass plant parts. Research indicates that clippings do not contribute to thatch build up on grasses. Before you start returning clippings to your lawn, make sure you remove the thatch layer or is no more than 1/2 inch thick. A layer more than 1/2 inch thick will prevent clippings from coming into contact with soil microorganisms. If thatch is a problem in your lawn, use a vertical lawn mower or power rake to reduce the thatch layer. Once removed, you can use the thatch as a mulch or add it to your compost pile.
Can my mower’s bagging attachment be removed safely?
Be cautious about removing the bagging attachment from any lawn mower. Because many mower bagging attachments affect safety, it is very important to understand manufacturer guidelines before you consider removing the attachment. Some manufacturers have adapter or converter kits that can be purchased to change from a bagging mower to non-bagging type. Remember, never assume your mower is still safe to operate after removing the bagging attachment. Refer to your owner’s manual or equipment dealer to ensure you maintain complete safety.
What do I do if the grass is too long?
Avoid mowing when the grass is wet as this produces clumps that smother the lawn and clog the mower. If this occurs, or if grass becomes excessively long in between mowings, you have three options: (1) mow over the clippings a second time only if small sections of the lawn are wet or overgrown, (2) sequentially remove one-third of the grass blade then wait a day. Remove one-third again to get down to the desired height over several mowings, (3) bag or rake the clippings to use as a mulch, a soil additive, or an ingredient in your compost pile.
Are mulching mowers any more effective than regular lawn mowers?
Mulching mowers are rotary mowers that cut clippings into smaller pieces and disperse them uniformly back into the lawn for decomposition. Removing only a third of the vertical green growth is very important when using a mulching type of mower. Well-designed mulching mowers distribute clippings more evenly across the lawn surface than regular lawn mowers. Regardless of mower type, the key to a quality cut is keeping the mower blade sharp and properly adjusted. Dull mowers use more gasoline, give the lawn an undesirable frayed appearance, and can allow leaf diseases to get started. Mower blades require sharpening at least every second mowing season for bluegrass lawns, and at least once per year for tall fescue or perennial ryegrass lawns.
Are there any situations when I should collect the clippings from my lawn?
When the lawn is heavily diseased, removing clippings can help to decrease the level of disease organisms. Clippings can still be used for compost. If the lawn must be mowed when wet or excessively tall, clippings will mat together and may not be evenly distributed. The lawn may be damaged under clumps of clippings. If your mower is unsafe to operate without a bagging attachment, clippings can be collected. Use the clippings as mulch or for compost.
If clippings are collected, can they be used for mulch or in a compost pile?
Yes, grass clippings used as mulch should be built up gradually to a 1-inch layer using dry grass. Greater thickness can inhibit the penetration of moisture and oxygen into the soil, and excessive heat and foul odours may develop. Mulching thickness can be increased by mixing in a 1:1 or 2:1 ratio of compost, dry leaves or wood chips with fresh grass clippings. Grass clippings also can be used in a compost pile. The additional nitrogen grass clippings supply will help speed up the decay process. However, large amounts of fresh clippings, all at one time, can create odour problems. These temporary odours can be reduced by mixing compost, dry leaves or wood chips in a 1:1 or 2:1 ratio with clippings before composting.

I hope this column has provided the information that you need to think about joining the “Don’t Bag it Plan”. If you do, cutting the grass may just become an enjoyable yard chore.