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Grasscycling: Waste Not, Want Not

Gardening, Landscaping, Landscaping, Lawn and Garden, Outdoor Living July 7, 2020 Matt Weber



Everyone knows the process of mowing grass can be a time-consuming, two-phase operation. Once the grass is mowed, the work’s still not over. If you’re sick of spending your weekend collecting grass clippings, you’re not alone. Faced with the longstanding question of how to deal with the clippings left behind after a long afternoon of mowing, CalRecycle offers a fresh approach — do nothing.

In California and many other states, lawn clippings comprise a surprisingly large portion of the waste stream. California lawns can generate approximately 300 to 400 pounds of grass clippings per 1,000 square feet annually, depending on turf variety, environmental conditions and turf-management practices. This can equate to as much as 8 tons per acre each year. Much of this valuable green material is being wasted in landfills rather than being reused in the very urban landscapes that generate it. In response, landscaping industries are paying more attention to practices that reduce waste generation, reuse trimmings on-site and recycle organic products back into the urban environment — something homeowners should consider for the sake of their time, labor, lawn care and the health of their surroundings.

One such technique is grasscycling, the natural practice of leaving clippings on the lawn when mowing. The clippings quickly decompose, returning nutrients to the soil. This practice, in conjunction with a proper turf-management program, can reduce water and fertilizer requirements, as well as mowing and disposal time.


Big Benefits “There are a number of benefits to grasscycling,” says Ken Decio, Senior Environmental Scientist. “First of all, it’s a timesaver. By grasscycling you don’t have to bag your clippings, stop the mower, take off the bag, empty the clippings, reattach the bag, etc. Eliminating this saves a lot of time.” And if your mower isn’t equipped with a bag to catch the clippings, you can give the rake a rest.

“It also saves money and helps the lawn,” says Decio. “Grass clippings contain nitrogen and other nutrients, so leaving them on the lawn to decompose actually returns these nutrients to the soil. This can cut down on fertilizer costs.” Not only does this organic matter benefit the grass, it provides nutrition to the soil, resulting in a healthier stand of turf. “I’ve heard different estimates,” he adds, “but a ballpark figure would be that about 15 to 20 percent of your fertilizing requirements can be supplied by grasscycling, so you could probably get by with a quarter less fertilizer.”

But the benefits of grasscycling don’t stop with your yard. The surrounding locality will reap environmental benefits. “One of the biggest advantages for the community is that grasscycling reduces green waste,” says Decio. “Leaving the green material means it doesn’t end up in landfills. Plus, since clippings left on the lawn are composed primarily of water, you don’t have to water the lawn quite as often.”

The reduction in water and fertilizer requirements in turn reduces the problem of storm-water runoff. “Storm-water runoff is becoming a huge issue in California and I’m assuming in other parts of the country as well,” says Decio. “There’s a lot of overwatering, overfertilizing and pesticide use, and a lot of that is transported through the water. If someone irrigates their lawn after these chemicals have been added, these pollutants can flow directly into storm drains, local creeks and rivers without being treated by the sewer system.”

The Basics Grasscycling, if performed correctly, can benefit most types of grass and work in most types of weather conditions. Decio notes that mowers with mulching capacity achieve the best performance. Mulching blades cut and recut the grass blades into smaller pieces than standard mowing blades and blow them down into the turf. These short clippings are not very noticeable on the lawn and they quickly decompose.

Mulching mowers are available as dedicated machines, new multitask units or even as retro-fit kits that convert your side-discharge mower into a mulching unit by adding mulching blades and a cover for the discharge chute.

Simply operate your mulching mower as you would a conventional unit but pay close attention to the cutting height. “Follow the One-Third Rule when mowing,” notes Decio. “Only cut off one-third the length of the grass blade during any one cutting. If you’re only cutting a third of the grass, you’re obviously producing very short clippings. The shorter the clippings, the faster they decompose. Plus, if you cut more than one-third the length, you’re cutting off the food-producing tissue of the turf, which causes the lawn to weaken and thin.” And a thinning lawn encourages weed invasion and makes the turf more susceptible to pests.

Of course, there are exceptions to every rule. Decio provides the example of someone who has gone on vacation for a few weeks. On returning the homeowner finds his lawn overgrown, flourishing at 5 inches while he prefers only 2. The CIWMB recommends cutting the lawn down to 4 inches. A week later, cut it from 4 inches to 3, and then from 3 to 2, gradually lowering the lawn’s height. Shearing it down directly from 5 to 2 inches greatly stresses the lawn, as well as results in unsightly mounds of grass clippings.

What about Thatch? “One of the issues that cause people to initially oppose the idea of grasscycling is the issue of thatch,” says Decio. “That’s something that seems to have been passed down from generation to generation the idea that if you leave grass clippings on the lawn it will cause thatch buildup and turf problems.”

However, research has shown that grass roots are the primary cause of thatch, rather than grass clippings. Thatch is composed primarily of roots, stems, rhizomes, crowns and stolons, the woody parts of grass that contain lignin. Lignin doesn’t decompose very quickly. Grass clippings, on the other hand, are composed of 80 to 85 percent water with only small amounts of lignin and they decompose rapidly.

Using mulching blades, finely cut about 1/3 the length of the grass blades, allowing the clippings to remain on the lawn and return nutrients to the soil.

Decio notes that certain types of grass, such as Bermuda, Kikuyu and Kentucky bluegrass, have higher amounts of lignin than typical cool-season grasses, making them a bit more thatch-prone. “But from the research we’ve gathered,” he adds, “grasscycling affects thatch buildup by such a minimal amount that the advantages far outweigh the disadvantages.” The CIWMB reports that a small amount of thatch (approximately 1/2 inch) is actually beneficial to the lawn, providing insulation to roots while serving as a mulch to prevent excessive water evaporation and soil compaction. It may even help create a cushioning effect on the lawn.

Cut to the Chase The bottom line is simple: Grasscycling can benefit your pocketbook, your lawn and your environment. However, a proper turf-management program is key to achieving these results.

“Grasscycling is not only the act of leaving clippings on the lawn. To make it work, you also have to water, fertilize and mow properly,” says Decio. He points out that many homeowners in Southern California have a tendency to overwater and overfertilize, due in part to a flat billing fee for their water consumption, neutralizing the incentive to conserve. As a result, their lawns grow very quickly, producing a lot of green material. Naturally, if the grass is growing extraordinarily fast and you continue to leave the clippings on the lawn, the results can be an unhealthy mess for the turf. Thus, a proper turf-management regimen involves setting an appropriate pace for lawn care.

“Grasscycling does produce a healthier soil by returning organic matter,” says Decio. “But if you add so much water that the grass clippings are floating, the process isn’t doing you a whole lot of good.”

Editor’s Note: For more information on grasscycling, visit https://www.calrecycle.ca.gov/organics/grasscycling

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