If you have a lawn, you will be faced with the dilemma of what to do with your grass clippings when you or a garden service mows your lawn. Many people rake grass clippings and dispose of them. Others leave them on the lawn, raking the lawn clippings to use as mulch in the garden.
The question of whether to leave your grass clippings on your lawn or pick them up is largely one of personal choice. But, the benefits of leaving them and not removing them generally outweigh any disadvantages. If you choose not to leave them on the ground, you could collect them to use as mulch or to add to your compost heap.
What are grass clippings?
Grass clippings are produced when you mow or cut your lawn. Lawns stay healthy when they are mowed regularly, so the clippings are essentially the result of a good lawn care program.
However, many people consider grass clippings to be unusable garden waste. This is why they rake them up and bag them.
But when you recognize the potential uses of grass or lawn clippings, you’ll wonder why you haven’t been keeping this “waste.”
Can you just leave grass clippings on the ground?
The simplest way to recycle grass clippings is to leave them on the lawn. So, yes, you certainly can just leave grass clippings on the ground.
But there are a few caveats. The first is that you need to mow lawn grass often.
As Tom Cook, a turf grass specialist from Oregon State University says, if you mow once a week during the growing season, your lawn quality will improve. He also points out that lawn clippings are an excellent source of nutrients.
Research, he says, shows that we can halve the quantity of fertilizer we normally use to keep our lawns healthy. A proviso is that you should use a mulching-type rotary mower that returns clippings evenly to the ground.
His own experience proves that it is possible to maintain “acceptable quality” lawns growing in clay soils without adding fertilizer. He did this (or rather didn’t) with his own lawn for about 12 years.
Also, if you’re leaving grass clippings on the ground, they shouldn’t be too long. Extension educators from the University of Minnesota advise ensuring they are no longer than an inch.
Shorter lawn clippings will literally filter down through the unmown grass to the soil surface where they will decompose more quickly. If they are too long they are more likely to smother the living lawn and damage it.
A good rule of thumb when mowing is to remove no more than one-third of the blades of grass. This is another good reason to mow grass lawns often.
Pros and cons of leaving grass clippings on the lawn
Grass clippings contain valuable nutrients that will make their way back into the soil if you leave them on the ground after mowing. On average, lawn clippings contain about 1% phosphorus, 2% potassium, and 4% nitrogen.
These are the most important chemical elements needed for plant nutrition, with nitrogen being the most important for lawns. Chris Starbuck of the University of Missouri Extension reckons when grass clippings are left on the ground, they provide as much as 25% of the lawn’s fertilizer needs.
Also, if you leave them on the ground, you’re going to save yourself the time and effort of raking and bagging them.
Many people believe that a con of leaving grass where it is on the lawn is that it promotes the build-up of thatch. Thatch is basically a layer of grass stems, roots, runners, and so on that build up between the growing lawn and the soil.
Chris Starbuck points out that grass clippings contain as much as 85% water. This makes them decompose a lot quicker than other parts of grass plants, or of other plants.
There’s been lots of research into this and, almost without exception, it proves that this (thatch build-up) doesn’t happen. According to Tom Cook, that is much more likely to happen when the mowing height of grass increases.
Is it better to pick up grass clippings?
There are times when it’s a good idea to collect grass clippings. For example, if you have allowed your lawn to get too long or if the clippings end up in matted lumps.
Otherwise, it’s generally best to leave them on the ground. As long as they are dry, you can give them a quick rake to cover the surface of the lawn more evenly.
Other uses for Grass Clippings
The most common “other” uses for grass clippings are to use as mulch or to add it to your homemade, home-grown compost.
Grass Clippings for Mulch
Organic mulch is invaluable in the garden and there are lots of materials we can use. Grass clippings are just one sort, but it is used in exactly the same way as we use straw, leaves, and bark mulch.
If you’re going to mulch grass clippings, all you need to do is put the mulch around flowers, shrubs, vegetables, and even trees, rather like the way nature does it when not interfered with. It conserves moisture in the soil, maintains soil temperatures, and helps to reduce weeds.
There are a few provisos to be aware of. For instance, don’t use more than a couple of inches of clippings.
Also, only use dry grass clippings. Wet clippings can do more damage than good because they prevent moisture from getting into the soil and tend to reduce oxygen content. A lack of oxygen will tend to result in offensive odors developing when decomposition takes place.
Also, avoid using your grass clippings as mulch if you treated the lawn with a herbicide recently. As mentioned above, the same caveat applies to leaving clippings on the ground after you’ve mowed.
Grass Clippings for Compost
The best organic compost is made from a mix of natural plant materials. As such, lawn clippings are an ideal addition to the pile because of their high nitrogen content.
However, don’t ever try to make compost using only grass clippings. Anaerobic decomposition will take place without oxygen,
which will tend to smell really bad.
Add other types of garden waste including dry leaves or straw, shredded branches, and so on. Also, include a small amount of soil to introduce the microorganisms that will start the decomposition process.
Ultimately, most grass clippings are simply too valuable to waste. If you leave them on the lawn, they will usually decompose rapidly, and the nutrients will filter into the lawn and the soil beneath it.
If you have allowed your lawn to grow very long, then rather use those clippings as a mulch or as an ingredient in your compost. Just don’t trash it.