top of page

Autumn lawn care 1 - thatch and the importance of worms.

As the days start to get shorter so the rate of growth of your lawn - and the way in which you cut and look after it - starts to change.

We tend to cut our lawn less frequently than we do when it's growing well in the summer and we set the cutting height on the mower so that the grass is left slightly longer. For a typical lawn we'd cut once a week and leave the grass about an inch long.

The other important jobs that we consider now are ones that make sure the lawn is given as best a chance as it can have to rest up over the winter and to be ready for everything the following spring and summer can ask of it!

What is thatch?

Thatch is simply the accumulation of left behind cut grass and dead grass roots.

Try as hard as we might it's really difficult to catch all of the grass that is cut over the season. Whilst it's good practice to use some of the cuttings as a mulch, too much mulch can start to harm the lawn.

Thatch that is under control is good for your lawn as it creates a buffer that can protect it. Too much however, and when new roots from your lawn start to grow in it, is when we start to see problems.

Grasses propagate by seed. Some also produce side shoots or runners. These side shoots help the grass spread and are either just above the soil surface or just below it. This spreading helps the turf knit together and become thick and dense.

Why worms are important.

The thatch layer increases when the production of new shoots exceeds the rate at which the dead ones decompose. Thatch is naturally broken down by the micro-organisms - worms - in the soil. However there are several factors that can be detrimental to our worm populations and this leads to an excessive accumulation of thatch.

Soil type: Soils with a high sand content tend to have fewer worms. Soils with a high loam content tend to have more worms. As we've said worms play an important role in the breakdown of thatch.

Soil pH: A soil that is more acidic is likely to have a negative effect on our worms. Therefore the rate of decomposition is going to be reduced.

Over-feeding: Carefully applied fertiliser is essential to the overall health of the lawn. However too much nitrogen will produce rapid, lush shoot growth that only adds to the thatch layer.

Over-watering: Excessive irrigation will have an influence on decomposition. Our worms need air to survive and reproduce. They tend not to thrive well in wet soils.

Lack of oxygen: A lack of air in the soil - often caused by over-watering or soil compaction - will also have an adverse effect on our worms.

If the thatch gets out of hand then your lawn will start to suffer. The grass won't grow as well as it might - and we'd like - and over time we'll start to see bare patches. And where there are bare patches we'll eventually see weeds and moss starting to take root.

So for now - and particularly at this time of the year - we're going to start to address some of the causes of the thatch possibly starting to build up.

Firstly we'll look at scarifying. This is simply the physical removal of the thatch. There are two ways to do this - both require some physical exertion! You can either use a scarifier - a specialist wheeled tool that has vertical blades that cut into the lawn and loosens and teases the thatch - or you can use a lawn rake. Using only moderate pressure and lifting the rake frequently, the thatch will soon start to lift.

Normally we'd scarify in the autumn - when your lawn has a chance to recover. Initially it will look slightly messy and will need some warmth, sun and rain to encourage the new grass to start to grow and fill the areas that were previously thatch.

If the weather looks as though it's going to be good - usually in late August or September - and if your lawn isn't shaded by other plants or buildings then early autumn is a good time to tackle it.

If though the lawn is shaded, or if you've missed that opportunity, then it's probably better to leave it until the growing season starts again in the following spring. We'll talk then about how we prepare the lawn for scarifying and how we tackle it.

What we would do now though is aerate the lawn. This is one of the most effective ways of preventing thatch as it helps encourage a healthy worm population. As we know worms are essential in decomposing the organic matter and preventing thatch accumulation.

Aerating your lawn is simply making holes in it. This releases the soil compaction and encourages better growing conditions - by getting air and nutrients into the soil - and in turn encouraging better conditions for our worms.

We need to consider the type of soil we have and when and how we aerate. If the soil is sticky or heavy clay then using a fork to create the holes will simply compact the surrounding areas even more. In that instance we need to use a hollow tine aerator.

So the tools. Well we have a variety to consider - much depends on your soil, budget and lawn size. As we said just now using a lawn spike or garden fork is something that could be used - but if one of the things we're trying to address is compaction then we have to ask ourselves whether using a spike or fork will actually address that. Where will the soil go from pushing the fork into the lawn?

If your lawn isn't that large and as an initial attempt we'd recommend lawn sandals or a lawn aerator. Both tend not to go into the lawn to the same depth as a garden fork and tend not to compact the surrounding area so much. The sandals are simply like - well a pair of sandals (!) that you strap onto your shoes or wellies and use when you walk on the lawn.

They have spikes on them that do the job for you! A lawn aerator is a specialist tool that looks a bit like a push along lawnmower with spikes on it. Easy enough to use but personally I like the sandals!

The other tool that's worth a mention is a hollow tine aerator. This looks a bit like a garden fork but rather than have spikes it has hollow tubes. This means that when you push that into the lawn a "core" is removed. This is great as it really does help address the issue of compaction and creates far more effective areas in your lawn where nutrients and air can get into.

And then of course there are more specialist tools - weighted rollers that you can use behind your sit on mower or powered tools. Great if you have a really large lawn or golf course but probably beyond the need or reach of most of us.

If you think your lawn might benefit from a bit of TLC then please do get in touch either through my facebook page, at or on 07734 365028. We might not be able to get yours to a putting green standard but we'll give it a good go!


bottom of page