The general recommendation for managing grass clippings during the summer is simple: do not bag them. The practice of leaving fine grass clippings on the lawn, often called “grasscycling” or mulching, is a beneficial lawn care strategy. Grasscycling is particularly advantageous in the hot summer months, contributing to both the soil’s nutrition and the grass’s ability to withstand heat and drought.
The Default Strategy: Mulching and Nutrient Recycling
Leaving grass clippings on the lawn allows them to act as a natural, slow-release fertilizer for the turf. Grass clippings are approximately 80 to 85% water, which facilitates their rapid decomposition, especially when cut into small pieces by a mulching mower. This quick breakdown releases essential nutrients directly back into the soil, feeding the lawn from the top down.
The most significant nutritional benefit comes from nitrogen, which is a major component of the grass blade. Clippings can supply a substantial portion of a lawn’s annual nitrogen requirement, sometimes up to 40% of its needs, effectively reducing the need for supplemental chemical fertilizers. This process, which also returns potassium and phosphorus, supports the growth of beneficial soil microorganisms that further break down organic matter.
The steady, natural nutrient supply from the clippings promotes consistent, healthy growth rather than the rapid, short-lived growth spikes often seen with synthetic fertilizers. By retaining these nutrients, you are actively improving the soil structure and reducing the cost and effort associated with traditional fertilization programs.
Essential Summer Water Conservation
Beyond the nutritional benefits, leaving fine grass clippings on the lawn is a remarkably effective strategy for water conservation during periods of high summer heat and potential drought. The thin, finely chopped layer of clippings acts as a light, natural mulch over the soil surface. This layer insulates the soil, which helps to maintain a more stable and cooler temperature around the grass roots.
More importantly, this mulch layer significantly reduces the rate of water evaporation from the soil. By slowing the loss of moisture to the atmosphere, the clippings help the soil stay moist for longer periods after watering or rainfall. This physical barrier helps the grass withstand heat stress and can reduce the overall water needed for irrigation to keep the lawn healthy.
The improved moisture retention from the mulch effect encourages deeper root growth, which further enhances the turf’s drought tolerance. When the grass roots are cooler and have consistent access to water, the entire plant is better equipped to survive the heat of midsummer.
Specific Scenarios Requiring Bagging
While mulching is generally the best practice, there are a few specific circumstances in the summer when you should elect to bag the clippings instead. The first exception occurs when the grass has grown excessively long between mowings, especially if you violate the “one-third rule.” This rule suggests removing no more than one-third of the grass blade’s height at any single time.
When grass is cut too low, the resulting clippings are too bulky and heavy, which can lead to large, thick clumps left on the lawn surface. These clumps fail to break down quickly and can smother the healthy grass underneath, blocking sunlight and air circulation and potentially causing dead patches. In this situation, bagging the excessive clippings is necessary to avoid damaging the turf.
The second exception is when the lawn is actively suffering from a fungal disease such as brown patch or dollar spot. Fungal spores can be easily spread across the lawn by the mower blades and the dispersed clippings. Bagging and properly disposing of the infected clippings is a necessary step to physically remove the diseased material and help prevent the pathogen from spreading to unaffected areas of the turf.