How to overseed a lawn: Step-by-step

A green lawn with flower border
Overseeding can improve the health of your lawn (Image credit: Getty)

If you want to know how to overseed a lawn, Homebuilding and Renovating has put together this useful step-by-step guide.

Overseeding is the process of sowing new seed into an existing lawn to strengthen it with new, more suitable grass varieties. This thickens the lawn, gives it a more even colour, and improves its tolerance to shade and drought. It also helps achieve a smart looking lawn after mowing, especially if using one of the best petrol lawnmowers.

It is also environmentally friendly as it reduces the need to use chemicals to support your lawn, so you can improve your garden sustainably.

How to overseed a lawn: Step-by-step

David Hedges-Gower, the chairman of the Lawn Association, says the first thing you must do is correct the reason the grass died in the first place. If something like moss was the problem, you can read up on how to get rid of moss in lawns in our separate guide.

The next step is to choose a species native to the UK that will last, but also do most of the work for you.

1. Mow the lawn first When seeding the whole lawn with existing grass in, cut the lawn as short as possible. Do not feed the lawn for at least eight weeks before seeding.

2. Scarify the lawn Do this in multiple directions, allowing the machine blades to make soil contact. This will leave grooves for the seed to fall into. You can read more information on how to scarify a lawn in our expert piece.

3. Sow the grass seed Remove all debris and seed by hand in two diagonal directions for better coverage. Use 25-30g per square metre.

4. Consider adding loam If required, apply a loam-based dressing material (not sand) at a depth of 1-3mm and use a brush or the back of a rake to evenly distribute.

5. Rake, roll or tread Once the lawn seed has been sown, lightly rake the area before lightly rolling or treading in to help the seed take. This is crucial because it ensures that the seed has good soil contact, which will aid in its germination and establishment.

6. Water as often as possible Do not use a hose pipe (in most cases) as you only need to ensure the top 3-5mm is moist.

7. Feed After successful germination, apply a feed such as Truegrass at 30g per square metre to allow seed and existing grass to ‘marry up’ together. You can find this product on Amazon for around £15.

We also have a guide on how to sow grass seed if you need further guidance seeding a lawn from scratch.

A small lawn with huge floral borders

Finding out why your grass wasn't thriving is an important first step (Image credit: Getty)

Which type of grass seed is best for overseeding?

Guy Jenkins, an expert at Johnsons Lawn Seeds, says the first step to lawn success in your garden design is to decide what you need most from it.

He said: "Does your lawn need to be hard-wearing for heavy family use, is it mainly a space to relax in, or must it be low maintenance if you have little time for gardening? 

"Do you have shady areas with difficult dry ground, are you looking to create a showpiece lawn, or perhaps a country meadow effect? You might be seeding from scratch, repairing bare patches, or want a thicker lawn fast.

"You then need to keep those main aims in mind when choosing lawn seed and taking care of your lawn each season."

David says the best type of seed is a native one and a mix of bent and fescue seed is more sustainable.

Rye seed is the largest and quickest seed but is not a great long-term option because it doesn’t reproduce. It germinates quickly and because it only grows vertically, it can have a drastic effect on allowing enough light, air, food and water to the other native varieties.

Should I use a fertiliser when overseeding?

Gardeners should be careful when using fertiliser, such as Westland Safelawn from B&Q, on the lawn.

Overseeding is all about competition for new seeds against existing, stronger grass plants.

David says: “If you give the lawn feed prior to seeding, the existing grass will be growing and new seeds will not want to germinate.

“That said, most mistakes are made by not adding food when the new seeds really do need it – and that’s as soon as it has germinated.

“A seedling is weak and requires force feeding in its infancy. Applying a feed at the germination stage will allow it to quickly evolve into a stronger, healthier grass plant.”

Sam Webb

Sam is based in Coventry and has been a news reporter for nearly 20 years. His work has featured in the Mirror, The Sun, MailOnline, the Independent, and news outlets throughout the world.  As a copywriter, he has written for clients as diverse as Saint-Gobain, Michelin, Halfords Autocentre, Great British Heating, and Irwin Industrial Tools. During the pandemic, he converted a van into a mini-camper and is currently planning to convert his shed into an office and Star Wars shrine.