One of the biggest mistake’s enthusiastic gardeners make when cutting their lawn is to mow too low.

While many do not realise this, it can lead to all kinds of problems in your lawn including weed infestations and moss takeovers that will only get worse as time goes by. So how high should you cut grass? We’ll tell you in this guide.

The Ideal Lawn Mowing Height

The ideal mowing height for your lawn is a compromise between;

  • How high you think the lawn should be cut based on your aesthetic preferences
  • How much leaf coverage there needs to be for it to stay healthy

How High Do You Like the Grass?

Do you like your grass cut long or short? Ever given it much thought?

If a striped finish is what you want, then its best to keep some length. That’s because the effect of stripes will be much stronger than if the lawn were just trimmed short.

On the other hand, a “bowling green” finish requires a much shorter lawn.

From a lawn health perspective, the former is better. A low cut might look nice when conditions are perfect (meaning rain has fallen in abundance; sun shines every day; warmth surrounds us constantly and ample amounts of lawn feed have been applied) but often this isn’t the case. You would also need to mow at the best time of the day.

In general, the best type of weather for grass to grow is in spring and autumn. However, if the conditions change from this type of environment (such as drought, constant rain or constant frost), you’ll need to increase your lawn’s mowing height for it survive.

Learn more: When to Cut the Grass.

Keep Enough Leaf for Grass to Stay Healthy

If you have a formal or ornamental lawn, then chances are you won’t need to worry about kids and pets tearing it up. Therefore, the grass can handle closer mowing without being stressed from heavy use.

However, if your lawn serves as an area for entertaining guests or playing outside with family members, then keeping it short isn’t necessary or desirable. Not only will keeping it long create softer ground, but long blades of grass will keep enough sun trapped within them to make sure they get all their nutrients.

Lawn Mower Height Setting

The Rule of Thirds

When cutting the grass, the rule of thirds means you should never cut away more than a third of the grass leaf. Especially when mowing long grass. This ensures that your lawn is healthy and produces enough food for itself through photosynthesis to fuel its own growth.

As an example, if your grass is currently 9 cm in length, you’d want to remove no more than 3 cm at any one time. Anymore and you’ll remove too much of the leaf which will stunt root development and could lead to brown patchy areas.

How to Reduce the Height of Your Lawn Using the Rule of Thirds

It is now spring, and conditions are good. The grass was cut to 4 cm. However, it’s now grown to 12 cm.

Now you want to get it down to your preferred height of 4 cm as quickly as possible.

To mow in a way that won’t harm the grass, you’ll need to do it gradually.

Step 1

Give your grass its first cut and remember to remove no more than a third of the total length.

So, if the grass is 12 cm high, you want to remove a maximum of 4 cm. This will bring the height down to 8 cm.

Then let the grass recover and grow by a centimetre so its 9 cm high.

Step 2

Cut the grass again, removing a maximum of a third of the length, which in this example is 3 cm.

This will bring the overall height down to 6 cm.

Again, let the grass grow by a centimetre and reach 7 cm in height.

Step 3

Cut again by a third, which is 2.5 cm to bring the height down to 4.5 cm

Let the grass grow again to 5.5 cm.

Step 4

For this last cut, reduce the height by 1.5 cm. This will bring the height of the grass down to your preferred height of 4 cm.

To maintain your lawn at this length, never let the grass grow taller than 5.5 cm.

Maintaining Your Lawn at Your Preferred Height

Now you’ve got your grass down to its preferred height, there are two things that should never let happen 1) let the grass grow by more than a third 2) leave longer than 10 days between cuts.

Using our previous example, to keep your lawn at 4 cm tall you’ll not want to let the grass grow by more than 1.3 cm.

The shorter your lawn, the more often you’ll need to mow it to maintain that length.

Regular mowing encourages new leaves to grow from the base which means denser grass and less room for weeds and moss to grow.

How High to Mow Your Lawn: A Summary

As a handy to follow summary, I’ve provided a list of lawns types with a guide to their ideal heights below:

  • Family or utility lawns which contain ryegrass and get used a lot: 1-2 inches or 3-5cm.
  • Low use lawns that do or don’t contain Rye Grass: 3/4 – 1.5 inches or 2-4cm.
  • Ornamental lawns which consist of only fine grasses: 3/8 – 3/4 inches or 1-2 cm.
  • Shady areas: add 50% so if the rest of your lawn is an inch tall, make the shady areas are 1.5 inches.
  • Sloped areas: these dry faster than other parts of your lawn so make them 50% higher than the rest of your lawn.
  • Moss covered lawns: make sure the grass is at least half an inch taller than the moss.
  • In times of stress (drought, heat, cold or wet): mow high (50% higher).
  • If in doubt, always mow high.

Final Verdict

The answer to the question ‘how high should you cut grass?’ changes based on the time of year, the type of lawn you have and how you use it.

If you follow the rule of thirds as well as my general summary to mowing heights, you’ll never cut the grass too short again and your lawn will be healthy year round.