Mowing your lawn BEFORE overseeding — this is how it works!

It’s a schoolboy/girl error — forgetting to mow before overseeding. It’s not the end of the world, but your lawn will look mighty untidy for a while if you don’t cut beforehand. 

Because your existing grass will grow around your newly seeded grass plants — and you can’t mow until they’re established. 

Don’t worry — it can happen, which is why I’m writing this short blog piece, reminding you why you should mow before overseeding! 

What is overseeding?

Overseeding is one of the most effective ways to keep your lawn young and robust, providing a dense turf that will keep weeds and moss at bay. 

However, it can take up to four weeks for the new seed to germinate and grow to the point it’s ready for its first mowing. And all the while, your existing lawn continues to grow. 

Sure, you can mow around the overseeded areas if they’re in patches, but it’s better to leave your lawn undisturbed to ensure the new grass plants aren’t damaged. 

So, cut your lawn a little shorter than usual before overseeding. 

Why overseeding creates a denser lawn

When you overseed, you spread fresh lawn seeds over your existing lawn, paying particular attention to any bald spots. This means that your lawn will fill out with new, young blades. 

This is important because grass plants don’t last forever — over time, they become depleted and more susceptible to disease. Most grass plants last five years at their peak, and it’s downhill from there. 

So, by overseeding, you keep your lawn young, healthier, and more resistant. You’ll develop a denser, more beautiful turf, which has a better chance against diseases, moss, and weeds. 

Why is overseeding important?

There are two principal reasons for overseeding:

• Lawn rejuvenation: overseeding replaces old, dying grass with fresh, young plants, which help protect against weeds, moss, and disease. 
• Lawn preservation: as soon as bald spots appear in your grass, weeds and moss will force their way into your lawn. By overseeding, you’ll prevent the likelihood of bald spots, which helps prevent weed invasions! 

When should I overseed my lawn?

The best time to overseed is during the spring or autumn because the soil is warm enough to germinate the seeds, and there’s more likely to be regular rain to relieve you of the constant watering you’ll need to do to help your young plants on their way to maturation. 

However, if you’re attacking weeds, pests, or a lawn disease, you can overseed whenever the bald spots appear due to weed death or pest removal. 

However, lawn seed will only germinate when the soil temperature is at or higher than 10℃, so it won’t work in the depths of winter. 

Remember: always use a lawn starter fertiliser to boost the soil’s nutrition so your baby plants will grow into healthy adults.  

How to prepare the lawn for overseeding

Lawns don’t grow in a day! High-quality seeds tend to take up to 4 weeks to germinate and grow to a strength sufficient for the first mowing. 

And this is why it’s essential to mow before overseeding because your established grass plants will be huge after four weeks. Remember, new grass plants need direct access to sunlight and air — if the surrounding grass is too long, it will put your new plants in the shade. This leads to humidity and, ultimately, mould, which can kill your new plants. 

So, mow to 3cm before overseeding. This is shorter than a typical cut but will ensure plenty of light and air for your young plants to thrive. 

Preparing the soil for overseeding

Healthy grass grows on healthy soil, so two things are essential:

1. The nutrient content of the soil
2. The type of soil

Fertilise your soil

Supply additional nutrition via regular fertilisation. I recommend fertilising your lawn at least three times a year for optimal results. If that’s too much, aim for early spring and late autumn. That way, the soil will be in good condition to support your grass plants when they need it the most.

Check out our expert guides on fertilising your lawn and understanding your soil needs. 

Test your soil

To determine your soil type, just grab a handful of earth and squeeze it in your palm. If the mud sticks together firmly, you have clay soil; if it falls apart when you release your palm, you have sandy soil. 

If you have clay soil, you’ll need to aerate regularly to ensure it doesn’t become compacted. You may need to improve the ground with water-retentive organic matter if it’s very sandy. 

Find out more about improving your soil in our expert guide to improving soil quality. 

Which lawn seeds should I choose?

It depends on your garden conditions. If your lawn is in full sun all day, then you have the widest choice of grass seeds — choose either a robust lawn seed for heavy use or an ornamental lawn seed for beautiful grass that can be cut short. 

If you have a shady garden, you’ll need a lawn seed that copes in both sun and shade, so try out our Shade & Sun grass seed.

Check out our wide range of lawn seeds for all gardens. 

Top tips for mowing before overseeding

Before overseeding, follow these tips:

1. Remove all debris from the lawn surface, including stones, branches, and leaves. 
2. Remove garden furniture and anything that will put the lawn in the shade.
3. Cut out the weeds, and immediately fill the holes with good topsoil. 
4. Move your lawn to 3cm. 
5. Sow your grass seeds by hand or with a hand spreader.
6. Lay a lawn starter fertiliser. This supports the seedlings as they grow. 
7. Keep your lawn moist for 14 days — spray it three-to-four times daily. Little and often is better than one extensive watering, which could displace the seeds. 
8. Remove weeds as they grow, and avoid walking on your lawn for four weeks. 
9. After four weeks, mow. And enjoy your lawn! 

Thanks for reading!

I hope you’ve got all the info you need for a successful overseeding project. But if you have questions, get in touch!

We’ll reply asap!

Happy overseeding.