How Long Does It Take For Grass Clippings to Decompose?

Turf specialists recommend you leave grass clippings on your lawn after mowing. Grass clippings decompose rapidly, and within a few weeks, they will start providing valuable nutrients and mulch to the growing grass. So, how long does it take for grass clippings to decompose?

It takes about 4 weeks for well-spread grass clippings to decompose on the lawn completely. This period may vary depending on the size of the clippings, grass type, and weather conditions.

Excess grass clippings on the lawn, more than an inch thick, aren’t healthy for the grass. They will take longer to decompose and may smother and kill the grass underneath. For that reason, rake and bag the excess clippings for disposal.

Young grass clippings decompose faster than old ones. Warm and humid conditions also fasten the decomposition rate of organic materials.

Grass Clipping on the Lawn – Benefits

For many years, gardeners would rake and dump grass clippings. It was until turf specialists discovered that grass clippings are very beneficial to the lawn when left to decompose.

While there are many things to do with grass clippings after mowing, grasscycling comes with the following benefits:

  • Grass clippings decompose to release important nutrients back nitrogen into the soil for healthy growth of grass.
  • They add organic matter to the soil. Beneficial soil microbes feed on organic matter, and in the process, they aerate the soil and cycle major nutrients required by plants.
  • Grass clippings provide mulch that prevents the growth of weeds, water loss from the soil, and overheating of the soil during hot sun or drought seasons.
  • Leaving grass clippings on the lawn makes the mowing experience effortless and fun. Raking and bagging them is a time-consuming and labor-intensive process.
  • It takes less time for grass clippings to decompose while spread across the lawn than when they are piled in compost.
  • The process reduces the need for regularly applying fertilizer on your lawn or weed control products, which are unhealthy for the environment.

When to Trash Grass Clippings

While leaving grass clippings to decompose on your lawn is important, the following are circumstances under which you should rake and bag them:

  • If your lawn suffers from a fungal disease. This will help the lawn recover faster and prevent the disease from spreading to other healthy areas.
  • Remove excess grass clippings from your lawn and use them in compost. A thick layer of the material can block sunlight from reaching the grass, and this can damage or kill it.
  • Bag and throw away grass clippings that contain weeds. Using them on your lawn can encourage new weeds that may become hard to control.

How to Make Grass Clippings to Decompose Faster

Grass clippings left on the lawn have been wrongly blamed for a thatch problem in lawns. Thatch comprises dead grass roots, runners, and stems that form a barrier between the growing grass and the soil.

When thick (more than 1/2 inch), thatch prevents sunlight, water, and important nutrients from reaching the grass roots. In excess, thatch will also prevent the clippings from reaching the soil. This will limit the soil microorganisms from acting on them.

Thatch builds from unhealthy lawn practices like inadequate watering, poor drainage, improper mowing, and the use of too many fertilizers. A spongy feeling when you walk across your lawn is a major sign of thatch in your turf.

You should dethatch your lawn to enhance the healthy growth of your lawn grass. Do so if you also want to speed up the decomposition of any grass clippings on the lawn. Further, water your lawn adequately. Moisture and warm conditions usually accelerate a decaying process.

Too Much Grass Clippings on the Lawn – What to do

We have seen that too much grass clippings on the lawn harm grass. They will take longer to decompose, and in the process, they will also block sunlight from reaching the grass. When in excess, you should rake and bag them, then use them as follows:

  • Add them to your compost pile to add nitrogen
  • Dump them in your municipal compost bin
  • Use grass clippings as mulch in your gardens or flower beds to prevent weeds and keep the soil moist between watering.
  • Feed either fresh or dry grass clippings to your livestock
  • Give grass clippings away to community gardens or anyone who wants to use them.

Although fresh grass clippings are an excellent addition to compost, you’ll want to be careful about the recommended ratio of 30 carbon ingredients to 1 nitrogen ingredient. This means for every 30 pounds of fallen leaves, add 1 pound of grass clippings.

Too much grass clippings in compost can result in the production of foul-smelling ammonia gas. Additionally, grass clippings added to compost will break down slowly. You should therefore plan to add a little at a time if you want to avoid nitrogen overload.

Final Thought

Grass clippings are very helpful when left to decompose on the lawn. They enrich the soil with nutrients, humus, and mulch. Healthy grass clippings only take a few weeks to decompose completely. Excess grass clippings should be bagged and used in compost, donated, or dumped into a municipal compost bin.


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