Tony O’Neill, gardener and author of the popular “Composting Masterclass” and “Your First Vegetable Garden,” combines lifelong passion and expert knowledge to simplify the art of gardening. His mission? Helping you cultivate a thriving garden.
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To leave or not to leave grass clippings on your lawn is the question. Every lawn owner may have their own opinion, but there is a definitive right way of going about it.
Your lawn thrives on nitrogen which is abundantly present in lawn clippings. Grass gets suffocated by thatch, an accumulation of dead matter at the base of the plant. Clippings do NOT contribute to thatch problems; over-fertilizing does.
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Those are the essential facts, but additional considerations require your attention. This article will explore the roles of mowing, clippings, and thatch management in creating a beautifully healthy lawn. But before we proceed, consider the following facts:
- Adding yard waste, such as leaves, grass clippings, and branches, to your trash, has been banned nationally since March 1995
- Yard waste accounts for approximately one-fifth of all waste material
- Clippings left on the lawn could contribute as much as a quarter of your lawn’s total fertilizer needs
- Because clippings contain as much as 80 to 85 percent water, they decompose quickly
- Not having to bag clippings can reduce the average mowing time by as much as 50 percent
When fully considered, grass clippings make up a surprisingly large portion of waste – approximately 300 to 400 pounds of grass clippings per 1000 square feet annually or, put differently, six-and-a-half tons per acre each year. Grasscycling is the solution, reusing this valuable resource.
The following quotes from a study done by the NASA Earth Observatory site add perspective.
After running a series of model simulations using different amounts of fertilizer, watering schedules, and leaving or removing the cut grass after mowing, Milesi says that a well-watered and fertilized lawn is a carbon sink.
If people recycle the grass clippings, leaving them to decompose on the lawn, the U.S. lawn area could store up to 16.7 teragrams of carbon each year. That’s equivalent to about 37 billion pounds—the weight of about 147,000 blue whales.
“The model suggests that if we recycle the clippings on the grass, we can almost halve the amount of synthetic nitrogen fertilizer. The carbon storage is still greater than it would be if we used the higher amounts of fertilizer but removed the clippings from the lawn.”
That could be good news for estuaries and other coastal areas where runoff of excess nitrogen from land surfaces is a major source of water pollution, leading to algae overgrowth and dead zones where aquatic life can’t survive. https://earthobservatory.nasa.gov/features/Lawn/lawn3.php
The Appeal of Cut Grass
A freshly mowed lawn appeals to our sense of order, beauty, and being alive. The smell of chlorophyll in the air is an active aid in creating and recalling happy times. The feel of freshly cut lawn under our bare feet is energizing. Newly cut grass feeds our general sense of well-being.
Gardeners want clippings removed because they believe drying clippings on a cut lawn breaks that sense of order. They may feel it looks untidy. So they collect that nutrient-rich product and have it added to some unseen landfill – wasted. The following are doable solutions that don’t require much effort.
Minimize Clipping Size
The correct guideline for lawn mowing is not to remove more than the top third of the leaf. Generally, the best lawn length is between 2½ and 4 inches, depending on the grass cultivar. If you’re creating a putting green in your backyard with some Bermuda Grass or Bent Grass, you want it low. But generally, you should cut your grass before it reaches 4 inches long, maximally removing the top inch.
The shorter your clippings, the less impact they have on your mowed surface. You may need to acquire a retrofit kit. Your local mower dealer can help you select a suitable one. Mulching mowers make grasscycling easy by cutting grass blades into small pieces and forcing them into the soil. Of course, an electric mulching mower will reduce air pollution.
A point to note. If your lawn has fungal growth, do not leave the clipping on the lawn. Instead, use the clipping as part of your compost heap. The temperatures generated by the composting process will break any organisms down. Fungal infections will present as white tips on the end of the grass blade.
Water After Cutting
Different grasses have different water needs. Warmer-season grasses need about 1-inch water a week in the growing season. Lawns watered too frequently tend to develop shallow root systems, making them more susceptible to stress and disease. Deep, infrequent watering produces a deeper, more extensive root system, enabling turf to resist disease and stress.
It is not advisable to water your lawn before mowing. Ideally, you want to cut in the morning, before it gets too hot, and then water directly afterward so the grass leaves can dry before sunset. Late evening and night watering can cause fungal growth.
Remember that it is better to water a deep soak 6 inches deep than more frequent light watering. If your lawn is in the peak growing season, you may need to cut it as often as three times a week.
Thatch Management
Thatch is the layer of dead plant material that forms at the base of the grass plant. Water and nutrients cannot reach the soil and grassroots when thatch accumulates to a thickness of more than half an inch.
According to research, thatch is caused by decaying grassroots, NOT grass clippings. Roots, stems, rhizomes, crowns, and stolons make up most of the thatch. These plant materials take a long time to degrade.
Because clippings are approximately 80 to 85 percent water, they deteriorate and decompose rapidly. Creeping grasses such as Bermuda grass and Kikuyu grass are more prone to thatch than other grasses. By raking the lawn with a metal rake, you can reduce thatch.
Machines that slice through the thatch layer to split it up are also available. A small layer of topsoil or compost on the lawn might also assist.
Microorganisms and earthworms help keep the thatch layer in check in a healthy lawn. They assist in the decomposing process and release nutrients into the soil.
Clippings for Compost
Sometimes grasscycling is not feasible. In instances where grass clippings are likely to be created in large quantities, such as prolonged wet weather, mower mechanical breakdown, or infrequent mowing, grass clippings should be bagged. Instead of throwing away grass clippings, consider composting them at home or in the community.
When properly handled and combined with ‘brown’ materials, this ‘green’ material can be an excellent addition to a compost pile. Clippings decay quickly, supplying moisture and nitrogen to the environment. Allow clippings to dry before adding them to a compost pile, layering them between other materials, and aerating the stack regularly.
Clippings can also be mulched around flower beds, trees, and shrubs to keep weeds at bay and minimize moisture loss. On the other hand, mulching with clippings should be discouraged with invasive species, such as Bermuda grass, or if the lawn has recently been treated with herbicides.
The Root of Healthy Lawn Growth
A healthy lawn, like most plants, is a product of five essential factors:
Seed Kind and Quality
Lawn types in the U.S. fall into either cool-season grasses or warm-season grasses. Universities and seed companies constantly research grass responses to drought, pests, and diseases and use applications to improve seed or vegetative reproduction.
Some new hybrids do not have seeding options and can only be purchased as turf sods. The National Turfgrass Evaluation Programme (NTEP) conducts extensive localized research on hundreds of grass types and offers the result without cost to the public.
| Warm Season Grass | Cool Season Grass |
| Bermuda grass | Kentucky Bluegrass |
| Centipede grass | Perennial Ryegrass |
| St Augustine grass | Fine Fescue |
| Zoysia grass | Tall Fescues |
| Bahiagrass | Creeping Bent Grass |
| Buffalo grass | |
| Seashore Paspalum | |
| Bentgrass | |
| Dichondra grass |
Soil Composition and Quality
Because we use the earth’s available underground water faster than nature can replenish it, saline water from the sea contaminates water tables in coastal regions. A growing presence of salt in the ground demands plants able to deal with the salinity.
Lawns grow best in loam soil – a balanced mix of sand, silt, and clay. Different grass types have specific pH requirements. You must test your soil annually and make only the necessary adjustments. If your soil is too acidic, add some lime; if too alkaline, add some phosphorus. Your local extension office can advise you on state legislation regarding the latter’s use.
Appropriate Nutrients
A key growth ingredient for your lawn is nitrogen. You need one to two pounds per 1000 square feet. Less is best, as too much does nothing but harm the environment. Grasscycling your clippings will reduce the required input by as much as 50 percent.
All fertilizer labels have three bold numbers. The first (N) is the percentage of nitrogen, the second (P) is the percentage of phosphate, and the third (K) is the amount of potash. These three numbers represent the primary nutrients (nitrogen(N) – phosphorus(P) – potassium(K)) and are a national standard. A bag of 10-10-10 fertilizer contains 10 percent nitrogen, 10 percent phosphate, and 10 percent potash.
You can also get fertilizers containing only one of the primary nutrients. Nitrogen sources include ammonium nitrate (33.5-0-0), urea nitrogen (46-0-0), sodium nitrate (16-0-0), and liquid nitrogen (30-0-0). Phosphorus is provided as 0-46-0 and potash as 0-0-60 or 0-0-50.
Calculating Nutrient Content
To calculate the pounds of nitrogen in a 50-lb bag of 10-10-10 fertilizer, multiply 50 by 0.10. Do the same for calculating the amounts of phosphate and potash. A 50-lb pack of 10-10-10 contains 15 lbs of nutrients: 5 lbs nitrogen, 5 lbs phosphate, and 5 lbs potash. The remaining weight is filler, usually sand or granular limestone. See more here.
Appropriate Watering
The national lawn guideline is one inch of water per week, including rainwater. Ideally, you want to add an inch of water once a week, but it all depends on your local temperatures. In hotter weather, you may need to up the ante.
Light and Care
Grass needs a minimum of 6 hours of direct sunlight a day. Some shade-resilient cultivars require less. An alternative is using groundcover for shady areas, such as Dichondra Repens. Your lawn will reward your care and attention. As with all living organisms, prevention is better than cure. Early identification of risks of diseases and pests will simplify the cure. You may find this turf care basics resource helpful.
Conclusion
In response to the initial question: “Leave or collect grass clippings off the lawn,” the answer is, “Leave that stuff be. It makes a HUGE difference to our environment and a significant difference to your lawn’s health.” Happy gardening, folks. And thank you for providing a carbon sink for our world.
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