Throgmorton: Grass Clippings – Bag Them or Leave Them

To leave grass clippings or not to leave grass clippings is the question. New studies and new mower technology says to leave clippings more often than collecting clippings.

Grass clippings are bagged up and thrown away because folks think the clippings look unsightly. But with new mowing technology you can’t even see the clippings. Mulching mowers chop grass into tiny particles. If you don’t have a new mower most old mowers can be retrofitted to mulch the grass.

Most grass is being mown taller. It’s recommended to grow bluegrass two and one half to three inches tall. With taller lawns even non-mulched grass clippings get lost in the long, growing blades.

A study by the horticulture department at CSU proves leaving grass clippings on the lawn is beneficial. Leaving lawn clippings improves the ecosystem, the soil and reduces carbon dioxide in the air. The study also shows leaving clippings reduce the need for nitrogen fertilizer.

As the clippings breakdown they build the soil. They add nitrogen and carbon to the soil. Both nutrients are essential for plant growth. When the soil holds the carbon, then less carbon dioxide is released into the atmosphere.

The study shows that twenty-five percent less nitrogen fertilizer can be used when clippings are left on the lawn. In fact if fertilizer isn’t cut back it counteracts the benefits of leaving the clippings. The study extrapolates over the long term nitrogen fertilizer could be reduced by half. Reducing fertilizer reduces the risk of nitrogen leaching into water supplies.

But leaving too many clippings can be a problem. The clippings build up as thatch. Thatch prevents air, water and nutrients into the soil (credit hollingworth). If it’s too thick it can suffocate the lawn. If you’re not using a mulching mower clippings should be left half the time and collected half of the time.

Using a mulching mower and leaving clippings could be a real time and money saver. Companies could save money on dumping fees and the time it takes to get rid of the clippings. The lawn owner could save money using less fertilizer.

All it takes is a little education. Leaving grass clippings builds the soil, uses less fertilizer and improves the environment.

Tom Throgmorton, of Throgmorton Plant Management, can be heard on KUNC, 91.5 FM, every Saturday morning at 7:35 and 9:35 a.m.

Originally published on August 2nd, 2011. Updated on September 21st, 2015.