What is the One Third Rule?

To keep a nice and healthy lawn you need to ensure you mow it at the right height and frequency. A simple rule to stick to is the “one third rule”. The one third rule refers to never taking more than one third of the leaf at any single mowing.

For example, if you have a Sir Walter DNA Certified lawn and you want to keep it at 25mm length, you would never let it get beyond 40mm in length. This may mean mowing more frequently than what you’re used to, but the result is a healthier lawn. Mowing more frequently won’t harm your lawn as long as you keep the blades on your mower sharp.

When you follow the one-third rule you actually respond to how fast your lawn is growing. During peak growing times (Spring & Summer), you will be mowing more frequently. Whereas in the cooler months you will be able to cut back. Even though you will be able to cut down mowing in the cooler months, it is important that you still regularly mow to keep weeds at bay. During winter, we still recommend that you mow at least every 14 days.

What If It Gets Too Long?

There may be some times throughout the year where you are unable to mow your lawn for an extended period of time. This may be due to holidays, heavy rain or for a whole range of reasons. If this does happen, it’s possible that your lawn can get quite tall. If your lawn has gotten very tall, mow it at the highest possible setting on your mower. It may take a little more time than if you took it all off at once, but what this does is prevents your lawn from going into stress and browning off.

You can either come back later the same day or later the next day and lower the height slightly and mow again. Keep doing this until you have gotten your lawn to the desired height you want.

Benefits of the One Third Rule

When you follow the one third rule it generally means you will be mowing more regularly which promotes lateral growth. What this means is that your lawn will grow across as well as up. When it grows laterally it will help to thicken up your lawn and produce a denser coverage. This helps to choke out the weeds and leaves you with a lush and healthy lawn.  

Another benefit of following the one third rule is the clippings. Because you are taking such a small amount off each time, you don’t need to use a catcher and can actually leave the clippings on the lawn. This helps to add nutrients into your lawn and can help reduce the need of using fertilisers, meaning less work for you!

The only time you wouldn’t leave the clippings on your lawn when following the rule is if you had weeds or seed heads. Then you would want to collect the clippings and compost them or dispose of them in your green bin.

Mowing Tips

So now that you know the importance of following the one third rule when mowing, lets go through a couple of extra tips to make sure you have the best-looking lawn on the street all year ‘round.

  • Watering the Lawn
    It is always best to mow the lawn when it’s dry. For best results try to avoid mowing during or straight after rainfall, if the lawn is moist from the night before, or if you’ve just watered it. Ideally you would mow your lawn first and then give it a water or time it before rain is due to fall.
  • Keep the Blades Sharp
    When you keep the blades sharp you stop any ripping and tearing which can cause damage and stress to the leaf. You will want to sharpen the blades a few times during the growing season, and may even want to have a second set on hand. 
  • Scalping
    You want to avoid scalping your lawn as much as possible (cutting the lawn too short). When the lawn is regularly scalped this leads to soil exposure, meaning your lawn is more susceptible to weeds, drought and high temperatures. It will also cause a poorly developed root system.
  • Time of the Day
    If possible, you want to avoid mowing the lawn during the peak heat of the day. In the afternoon or early morning is the best time to get the best results and keep a healthy, happy and nice-looking lawn.


For any questions or concerns regarding your lawn please contact our office on 02 4464 2033 or email us at sales@turfco.com.au.

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