How Long Does It Take For Grass Clippings to Decompose?

Leaving grass clippings on your lawn after mowing is highly recommended by turf specialists. 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 completely decompose on the lawn. This period may vary depending on the size of the clippings, grass type and weather conditions. Too much grass clippings on the other hand will take longer to decompose and may damage or kill the grass underneath.

Why you Should Leave Grass Clipping on the Lawn

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

  • Grass clippings decompose to release back important nutrients into the soil for healthy growth of grass. This include nitrogen, phosphorus and potassium.
  • They add the much needed organic matter into 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 prevent growth of weeds, water loss from the soil and overheating during hot sun or drought seasons.
  • Leaving grass clippings on the lawn makes mowing experience effortless and fun. Raking and bagging them is time consuming and labor intensive process.
  • It takes less time for grass clippings to decompose while spread across the lawn as compared to when they are piled in a compost.
  • The process reduces the need for applying fertilizer regularly on your lawn or weed control products which are all not healthy to the environment.

When to Trash Grass Clippings

While leaving grass clippings to decompose on your lawn is important, there are cases when you should bag and through them away.

  • Bag and trash grass clippings if your lawn is currently suffering from a fungal disease. This will help the lawn to recover faster and also 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 growth of weeds that may become hard to control.

How to Make Grass Clippings to Decompose Faster

Grass clippings left on the lawn has been wrongly blamedfor a thatch problem in lawns. Thatch is made up of 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 the similar manner, excess thatch will also bar the grass clippings from reaching the soil. This will limit the soil microorganisms from acting on the material.

Thatch builds as a result of unhealthy lawn practices like inadequate watering, poor drainage, improper mowing and use of too much 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 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 accelerates any decaying process.

Too Much Grass Clippings on the Lawn – What to do

We have seen that too much grass clippings on the lawn are harmful to your grass. The material will take longer to decompose and in the process they will also be blocking sunlight from reaching the grass. When in excess, you should rake and bag them, then:

  • 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 may want to use them.

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

Too much grass clippings in compost can result to production of foul-smelling ammonia gas. Grass clippings used in compost will breakdown slowly. You should therefore plan to add little at a time if you want to avoid nitrogen overload.

Final Thought

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


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