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Thatch is a natural part of your lawn, but if it gets too thick it can block air, water and nutrients getting to your lawn’s roots. It can also make your lawn excessively spongy and look unappealing.
Thatch is the living and dead grass shoots, stems, and roots that accumulate between the green growth tips and the soil surface. The benefits of thatch to your lawn and soil include:
- Increased resistance to lawn wear and tear of grass by absorbing impact
- Reduced compaction of the soil by providing cushioning
- Acting as mulch, insulating soil and grass roots from extreme temperature and reducing moisture loss
- Reduced water runoff and soil erosion
- Improved lawn health by breaking down to add organic matter to the soil and improving the lawn’s resilience.
Why excessive lawn thatch is a problem
Thatch accumulates excessively when lawn grows and dies faster than it can break down. Excessive thatch can lead to problems such as:
- The lawn is no longer level, with bumps and hollows developing
- The lawn is difficult to mow, with unevenness leading to “scalping” in patches, where the grass blades are completely removed
- The lawn is excessively spongy to walk on and difficult to move wheeled equipment on
Vigorous raking can help remove thatch from a small lawnGrassroots establishing in the thatch, leaving them exposed to heat and cold, leading to lawn damage
- The thatch becoming dense and compacted, especially in high-traffic areas, leading to water repellence and dead spots.
Which lawns develop excess thatch?
Lawn grasses are classified as either clumping or running. It is running grasses that tend to develop thatch.
Buffalo naturally has a thick thatch band, which is part of its appeal. It makes it more cushioned to walk and sit on. But the degree of thatch will vary greatly with the variety.
Kikuyu can develop a thick thatch due to its vigorous growth, but is excessive thatch is easily avoided through regular mowing.
Couch is a moderately thatching grass. It will generally only require dethatching if it has been neglected or regularly mown too high.
How to remove excessive thatch
Ryobi One+ Cordless Scarifier
Removing excessive thatch is labour-intensive yet straightforward. The removal process is known as scarifying or dethatching, and is ideally completed annually in spring to allow the lawn to regenerate quickly.
Raking the lawn
For smaller lawns, vigorous raking every couple of months during warmer seasons is easiest way to address excess thatch. For best results, use a spring-tine or spring-back steel leaf rake. Work over small areas with firm strokes, collecting and disposing of the removed material.
Machine scarifying
Vertical mowing, also called scarifying or dethatching, removes unwanted thatch using downward-pointing blades. Scarifiers or de-thatchers are used for this. You can rent larger petrol-powered machines for big jobs, but consider a smaller model for regular scarifying. Rechargeable battery models are available.
Top dressing
Top dressing raises the soil level to aid thatch decomposition. Use a fine mix like coarse-washed river sand or a blend with composted organics. Spread it evenly over the lawn, raking it into the thatch. Make sure you dethatch before top dressing, and aerate if the lawn is compacted.
An excellent example of dethatching was shared by experienced Workshop members @homeinmelbourne in their lawn renovation project.
How to prevent excessive thatch
Here are some tips for avoiding excessive thatch:
- Only apply quality lawn fertilisers at the recommended rates and intervals
- Regularly apply seaweed tonics such as Seasol hose-on, to boost biological activity in the soil and improve soil health. This will aid the decomposition of that dead material
- Don’t overwater. Keep watering just to the minimum required for the best appearance
- Mow at a reasonably low setting, keeping your mowing height consistent throughout the year, and alternate between using a catcher and mulch-mowing
- Aerate areas prone to compaction at least once a year with either a garden fork or a spiked roller
- Add top dressing each spring.
If you continue to have excessive thatch, consider whether your lawn variety is suitable for your garden. Sun-loving lawn varieties growing in too much shade will always stretch, leading to excess thatch.
Need more help maintaining your lawn?
The Bunnings Workshop community is here to assist if you have any specific questions about keeping your lawn healthy. Don't hesitate to hit the Ask a question button.
