Grass clippings can be used as mulch and has many pros including reducing moisture loss from soil, stops weed growth and adds organic matter to soil. Mulching with grass clippings can have cons if it is laid too thick including becoming too soggy, anaerobic, or smelling. This can attract bugs and mold can form on top of thick layers.
Grass clippings as mulch – Pros and Cons
|Protect plants and soil from frost||If laid too thick can become anaerobic and smell|
|Reduce moisture loss from soil||Can become soggy|
|Prevent weeds||Mold can form on thick layers|
|Adds organic matter to soil||Needs a carbon source to balance it out|
|Feed soil microbes and worms||Can attract bugs and flies if it gets too wet|
|Save on waste going to landfill||Can spread weed seeds|
|Contains nitrogen to support plant leaf growth||Can blow away in strong winds|
Pros of mulching with grass clippings
1. Protect plants and soil from frost
Grass clippings is a natural mulch which can hold frost up and away form the soil. This will also protect plant roots and help to regulate soil temperatures. Grass clippings will work best when mixed with other mulch types which will allow air movement.
2. Reduce moisture loss from soil
Grass clippings can form a fantastic mulch layer which will reduce the amount of evaporation and moisture lost from the soil. This will reduce the amount of water you will need to give to your plants and help to protect delicate surface soil.
3. Prevents weeds
Grass clipping mulch can stop the light from reaching weed seeds. This will stop them from sprouting and growing and make any weeds that manage to grow through easier to pull out. Grass clippings will keep the soil soft and make the roots of weeds easier to pull out.
4. Adds organic matter to soil
Grass clippings used as mulch will gradually break down adding more organic matter and carbon to the soil. This will help to improve soil structure which will increase drainage and support your plant’s root system to grow healthy.
5. Feed soil microbes and worms
Organic matter from grass clippings make fantastic food for soil microbes and worms. Microbes will come and break down the grass clippings and worms will dig up through the soil to eat the microbes and mulch. This increases the microbe balance in the soil which work to release nutrients making them available to your plants.
6. Save on waste going to landfill
Using grass clippings as mulch means that this organic matter does not end up in landfill. Organic matter in landfill causes a huge problem as it releases methane into the atmosphere. Keep grass clippings at home and use it as mulch or break it down in your compost bin.
7. Contains nitrogen to support plant leaf growth
Grass clippings contain nitrogen which will be broken down by soil bacteria. Plants love nitrogen and this nutrient is absorbed and used to support photosynthesis. Plant and leaf growth will be supported by the extra nitrogen released from the grass clippings to your soil.
Cons or mulching with grass clippings
8. If laid too thick can become anaerobic and smell
Grass clippings can start to break down anaerobically or without oxygen which can cause bad smells. Anaerobic breakdown by bacteria can release bad smelling gases and the grass clippings can rot. This is easily solved by mixing them with 2/3 dry brown materials like fall leaves, straw, hay or bark chips.
9. Can become soggy
Thickly laid, fresh grass clipping mulch can become soggy. Fresh grass clippings contain a lot of moisture which can become soggy if it is laid too thick. Let your grass clippings dry out first and mix with another dry mulch type to solve this problem.
10. Mold can form on thick layers
Wet, thick grass clippings used as mulch can encourage mold to form on the surface. This can happen particularly in shaded areas of your garden. Let your grass clippings dry out fully first and this can help to prevent mold.
For more on mulch fungus, check out my previous article here: Mulch Fungus: Types & Easy Treatment.
11. Grass clippings need a carbon source to balance
Grass clippings will need to be mixed with a carbon rich mulch to make it work best on your garden beds. Mix 1/3 grass clippings with a high carbon, dry mulch like straw, dry leaves or tree mulch. This will balance the moisture content and prevent mold.
12. Can attract bugs and flies if it gets too wet
Bugs, flies and ants can be attracted to rotting grass clippings as they have a high moisture content. To prevent bugs from being attracted to your mulch, dry the grass clippings out and mix them with bark chips.
13. Can spread weed seeds
Grass clippings that contain weed seeds should not be used as mulch as they may spread weeds throughout your garden. If you think the grass clippings contain weed seeds, place them in your green bin instead or break them down using a hot composting method.
Check out my previous article here: Why does a compost get hot?
14. Can blow away in strong winds
Dry grass clippings that have not been mixed with another mulch type can easily blow away in strong winds. Small, dry grass pieces can easily spread through your yard. Use these as the bottom ½ inch layer of the mulch layer and add a 2 inch cover of bark chips to hold it in place in windy spots.
For more on this, check out my guide to mulching in windy spots here.
Mulching lawn with grass clippings
Small amounts of grass clippings can be mulched directly into lawns. Trimming lawns regularly and using the mulching function on your mower can be a great way to improve soil structure. Lawn pieces mulched into ¼ inch pieces will naturally break down into the lawn.
Excess lawn clippings can be raked up. Make sure the lawn blades can still reach the sun otherwise lawn growth can slow.
Mulching flower beds with grass clippings
Grass clippings can be mixed with other mulch types including tree mulch to make the perfect mix to break down and improve the soil. A thin layer of grass clippings around ½ an inch can be placed on the soil first and then topped with 2 inches of bark mulch.
Grass clippings can also be mixed with bark or tree mulch in a wheelbarrow first and then laid onto flower beds up to 3 inches thick. This will prevent weeds and hold moisture in the soil. This will also feed soil bacteria which will break down the grass clippings releasing nutrients into the soil.
Mulching vegetable gardens with grass clippings
Grass clippings can be used on vegetable garden beds if it is mixed with 2/3 chopped straw, hay or sugar cane mulch. This will help both mulch types to break down quicker and at the end of the growing season it can be dug into the soil to prepare for the next season’s crops.
Use a mix of grass clippings with straw or hay around winter vegetables such as broccoli, cauliflower or kale. It can also be used under strawberries, peppers and tomatoes if mixed with these dry mulches.
How to use grass clippings as mulch
Layer grass clippings around ½ an inch thick or mix with other mulch types to increase the carbon content and prevent the grass from rotting on the ground. Mix with bark mulch or hay to increase air movement which will help with water penetration to the soil.
How to use grass clippings as compost
Mix 1/3 grass clippings with 2/3 of a brown material like bark mulch, hay, dry fall leaves or sugar cane mulch will form the perfect mix to break down over time and improve your soil. This can also be placed in compost bins to break down into rich humus or compost for your garden.
Grass clippings as mulch – Pros and Cons Summary
Grass clippings are a nitrogen rich mulch ingredient that works well when mixed with a brown mulch like fall leaves or straw. Don’t waste grass clippings by throwing them away, mix them into your compost bin, or add to the top of garden beds in a thin layer. Make sure they don’t have weed seeds first.
I am an accredited practicing dietitian, experienced gardener and a dedicated cook. I love writing and sharing my experience so you can learn from my successes and mistakes.