Can You Compost Grass Clippings?
Yes. Fresh grass clippings are a nitrogen-rich green, roughly 20:1 C:N, that heats a pile fast. Add them in thin layers mixed with browns, or they mat into a slimy, smelly layer.
At a glance
| Home compost pile | Yes |
|---|---|
| Green or brown | Green (nitrogen-rich) |
| Carbon to nitrogen | about 20:1 (approximate) |
| Moisture | Wet |
| Prep | None needed |
| Worm bin | With care |
| Bokashi | With care |
How to compost grass clippings
Spread clippings no more than 2–3 in (5–8 cm) thick and mix or layer them with about 2 parts leaves, straw or shredded cardboard. Let large loads wilt for a day first. If the lawn was treated with herbicide, check the product label for guidance on clippings before composting them.
Leaving clippings on the lawn (grasscycling) returns their nitrogen to the grass for no work. Bring them to the pile when you have enough browns to match.
What goes wrong
Thick, wet clumps of grass compact, go anaerobic and smell of ammonia or rotten eggs. Break up the mat, fork in dry browns and turn the pile. A few lawn herbicides persist through composting and can damage tomatoes, beans and other sensitive plants.
Worm bins and bokashi
Worm bin: Worm bins can take small amounts of wilted or dried clippings, but fresh grass heats up and can harm the worms.
Bokashi: Bokashi is meant for kitchen scraps; a handful of clippings is fine, but lawn-sized loads belong in the pile.
This counts as a green. Adding a lot of it? Check the balance with the compost mix calculator.
From hopcompost.com/can-you-compost/grass-clippings/ · General guidance, not professional advice.
Frequently asked questions
Are grass clippings green or brown?
Fresh clippings are green. Dried, straw-colored clippings behave more like a brown, though they still carry more nitrogen than leaves.
Why does my grass compost smell?
Thick layers of fresh grass pack down and lose air, which produces ammonia or rotten-egg smells. Mix in leaves or cardboard and turn it; more in why does my compost smell.
Can you compost grass treated with weed killer?
Check the product label. Some herbicides break down quickly, while a few persist through composting and can damage vegetables. When in doubt, leave those clippings on the lawn.