How to Add Grass Clippings to Compost

Adding grass clippings to compost is a great way to add nutrients to your pile. How and Why Should You Add It?

When I first began adding grass clippings to my composter, I was unsure if I was doing it correctly. When I started adding correctly, I realized why it was such a great green material.

Today, I’ll teach you how to add it to your pile.

Nutrient Composition

Grass clippings returned to the lawn can supply up to 25% of your lawn’s total fertilizer requirements. Clippings contain approximately 4% nitrogen, 2% potassium, and 1% phosphorus. The common fertilizer notation for this is an NPK ratio of 4-2-1.

Is It Good for Compost

Clippings are excellent for composting! They are high in nitrogen and contain just the right amount of moisture. When blended into the pile, they can assist in bringing the proper moisture balance to the center of the pile.

Grass clippings degrade quickly, allowing your compost pile to mature at a rapid rate.

Be Careful of Herbicides, Pesticides, and Insecticides

It is best to leave clippings that have been treated with pesticides out of the composting pile. 

Grass sprayed with insecticides registered for home use generally should be safe to add to compost piles. Insecticides degrade quickly in sunlight once it has been applied. The treated plant material can usually be used in the compost pile within one week of application. That being said, I still don’t recommend it. It’s better to be safe than sorry. 

Lawn clippings that have been treated with a herbicide should be kept out of the compost pile until you have cut the lawn two or three times. The types of herbicide typically used on private lawns can stay in the soil for up to 12 months. 

A person holding grass cuttings and fallen leaves for composting

How to Add to Compost?

  1. To gather grass cuttings, attach a mower bag.
  2. Compost any dry grass that hasn’t been treated in the last 14 days.
  3. Add the cuttings to the pile. If it is very wet, let it lay on top of the pile and dry out from the sun a bit.
  4. Mix brown and green material in a 2:1 ratio to achieve the proper carbon to nitrogen ratio. Brown material consists of brown leaves, branches, and newspaper.
  5. Mix and turn the pile every 1 to 2 weeks

How Long Does It Take to Decompose?

Most grass clipping compost piles will take 4 to 8 weeks to complete. In ideal circumstances, they can degrade in about three weeks.

Green or Brown?

Clippings, as you might expect, count as green material. This is not merely due to its green color but also because it is high in nitrogen content. Brown materials, on the other hand, have a higher carbon content.

A closeup picture of a lawnmower in action

What Helps Grass Clippings Decompose Faster?

Grass cuttings are already thin and short, which accelerates decomposition. You may help the situation even more by trimming your lawn more frequently so that the clippings in your pile are shorter. Another way to reduce their size is to use a mulching lawnmower.

Once the clippings are in your pile, make sure you have the right brown-to-green ratio, turn it weekly, and water when dry.

Jeffrey Douglas
Jeffrey Douglas own a landscaping company and has been in the business for over 20 years. He loves all things related to lawns or gardens and believes that proper maintenance is the key to preventing problems in the first place.
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