Why Is My Lawn Grass Going Brown?
A no-nonsense grass care guide, by a gardener
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The team behind DIY Gardening has created several popular guides for budding gardeners aiming to grow the perfect lawn in the UK:
- How to get rid of lawn moss
- The best grass seed for shaded gardens
- Over 40 lawncare questions answered by the experts
- The best lawn weed killer that won’t kill your grass
But what happens when the grass turns a brown/yellowish colour?
Is the grass dead? What caused it? Can the grass be rejuvenated and how long does this take?
Here, Daniel Woodley takes a look at what causes your grass lawn to turn brown and what you can do about it.
1) – Dormancy
When most people think of grass going into a dormant state, they think of winter when the temperature is so low and with so little light, the grass stops growing.
In fact, grass can also go into a dormant state during the summer where it stops growing.
As the ground dries, the roots cannot soak up much-needed water and nutrient uptake is also reduced. To protect itself, the grass will go into a dormant state where the blades go a brown/yellowish colour and may seem brittle to touch.
In most cases, the roots are dry and not growing but are still alive and simply waiting for the weather to improve. Specifically, they’re waiting for water, and lots of it.
There’s nothing wrong with allowing grass to go into a dormant state, it happens to all lawn grasses at some point and during the process, the roots will at first grow deeper in search of moisture. This growth helps to develop a strong root system – deep and strong roots are far more beneficial than shallow weak roots.
Unfortunately, a brown lawn isn’t a pretty lawn. You can, however, do a few things to prevent dormancy or bring your lawn out of it:
- Prevent your lawn from entering a dormant state by irregular but heavy/deep watering.
- Avoid shallow regular watering as this will only encourage weak, shallow rooting.
- Bring your lawn out of dormancy by heavy watering, regular at first, followed by a switch to deep irregular watering once out of summer dormancy. Based on my experience, it can take between two and four weeks of watering to bring a lawn out of summer dormancy.
- Apply iron sulphate to “green up” the lawn.
- Do nothing – the lawn will naturally recover as the weather becomes milder and there’s more moisture in the ground from rainfall.
2) Cutting Too Low or Too Aggressively
Cutting or strimming the grass too low risks scalping, this is where the entire grass blade has been cut off and the top of the root is exposed. This will turn brown and I’ve seen lawns take weeks to recover from this.
Scalping is often seen on uneven lawns where the grass had been cut far too low.
Also, the tips and mid-section of each grass blade are optimal for photosynthesis – the process of turning sunlight into plant energy. Cut them off and the grass will become stressed and unable to sustain its green colour, growth may also be slow, even after the application of lawn feed and watering.
I’ve always followed several rules of thumb:
- Never cut more than one-third of the grass blade in one go.
- If the grass is very long, cut it little and often over several weeks until the desired height is achieved.
- If you want to cut very low, make sure the lawn is as level as possible, otherwise, you may scalp any small mounds or raised areas.
- Avoid cutting low during very hot weather – grass should be longer during heat waves.
Damage from blunt lawnmower blades can lead to a browning of the grass blade tips, this can become very apparent when cutting the grass low so I suggest using sharp blades that cut, rather than tear the grass.
3) Shallow Rooting
I touched on this issue earlier in the article but it’s worth exploring shallow rooting further as there are several causes and shallow roots may result in your grass going into a dormant state much sooner. If the grass can’t get to water deeper in the soil due to shallow roots it will protect itself by going dormant and turning a brown/yellow colour.
The most common cause of shallow rooting is regular watering. With a plentiful supply of just the right amount of water, there’s no need for the roots grow deeper and stronger. As soon as it gets hot in the summer, the grass will be more susceptible to damage and dormancy.
The key is to only water the grass when needed, to water irregularly but heavily to encourage deep roots and to not be afraid of letting the grass dry out as the roots will do what all plant roots do when the soil begins to dry out; they will grow deeper.
Regular applications of fertilisers, especially those with high concentration of iron, can result in shallow rooting. Why would roots need to grow deeper when they are getting everything they currently need at their current depth?
Excess iron promotes sudden but leggy stem growth and bright green colour but often at the expense of root development.
Too much fertilizer, applied too often, just like excessive regular watering, can cause many problems in the lawn. These problems, such as early browning, won’t become evident until the warmer summer months when the grass really needs strong, deep roots.
4) Pet and Animal Urine
Pet urine contains nitrogen at such high levels it can kill the grass and roots within an hour of coming into contact with the ground.
Once the grass is dead, it can’t be revived.
Diluting the urine with a hosepipe is only a practical solution for the occasional mishap but I do have some long term suggestions if you own a dog and are seeing brown patches all over your lawn.
5) Fertiliser Burn – Lawn Browning and Yellowing
Fertilisers are made from mineral salts, which if applied too often or in too high a dose, can scorch or burn the grass, leaving it a brown or yellow colour.
Not all fertiliser burns are fatal to the grass, in many cases, the scorching will disappear after a couple of weeks of watering.
Here are the most common causes of fertiliser burn:
- Incorrect dosage of liquid, powdered or granular “quick release” fertilisers.
- Improper manufacture of the fertilisers resulting in a higher dose than stated on the packaging (rare but it does happen from time to time).
- Lack of care when using an applicator, burnt stripes in the lawn are often caused by an overlap; the grass has been given a double dose but only on the overlap.
- Spillage of fertiliser from hosepipe mixers, watering cans etc.
- By the user not watering in quick-release fertilisers which can leave deposits on the grass blade, burning them.
To avoid fertiliser burn, go with an organic option or try using slow-release granules. If a quick-release product is used, apply at a lower dose and water it in well.
6) Lack of Nutrients/Poor Soil Condition
Needless to say, a poorly lawn will be more susceptible to disease, stress and will likely enter a dormant state sooner that a healthy lawn.
Fertilisation at the correct dose, time and frequency can create a healthy strong lawn but other areas to look at are drainage and soil compaction.
Grass roots rarely grow deep into heavily compacted soil. Aeration as explained here, can help.
Also, excess moss can give the appearance of a brown lawn as it turns brown in strong sunlight (see how to kill lawn moss here). Do also consider that excess amounts of grass cuttings, especially long cuttings, can create a thick mat over the lawn. This smoothers the grass, weakening it and can lead to a browning of the lawn.
Explore more of our grass care help guides here, we’re sure you’ll find answers to any questions you have about overall lawn health.
7) Lawn Fungus/Disease/Insect Damage
Have you ever heard of the “pull test”?
A healthy, established lawn should contain grass that doesn’t easily pull out of the ground.
If the grass lifts out easily, then this could be due to insect damage (such as grubs), where the pest is eating the root system. With a weaker root, the grass is far more likely to turn brown or yellow sooner during the summer months. If you suspect grubs, look out for birds digging into the grass, it’s a tell-tale sign that there’s a pest underneath the grass. Also, try lifting some of the lawn, you should be able to see grubs quite easily if they are present.
Lawn disease can affect the grass at any time and weaken it, again leading to browning. Damp gardens are more prone to it.
Lawn fungus typically affects grass grown in damp conditions too, this is often due to regular overwatering or it could just be down to the location of the garden. Fungus is easy to diagnose – you’ll likely see rings of discolouration in the grass and it may pull up very easily due to the weakened root system. As with other types of disease, fungus can weaken the entire lawn which may not be evident until warmer months when it performs poorly, even with watering and fertilisation.
There are treatments available for lawn grubs, other pests and fungus infections but you’ll often need to change how you look after the lawn in the long term to stop a reoccurrence.
We hope you found this guide to lawn browning and yellowing to be insightful.
Explore more of DIY Gardening’s lawn care guides and articles:
Meet The Author: Daniel Woodley
Daniel has over 18 years of experience in the construction, home improvement, and landscape garden industries.
He previously worked as a project manager and has experience in managing teams of tradespeople and landscape gardeners on both small and medium sized projects.
Daniel is also a keen gardener and enjoys growing unusual plants and tending to his lawn.
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This guide was reviewed and fact-checked by Elizabeth Smith.
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