If your lawn is looking a bit thin, tired or patchy after the winter months, overseeding could be exactly what it needs. It is one of the simplest and most effective ways to bring life back into your grass without having to rip everything up and start again. Here in Dundalk and across County Louth, we see plenty of lawns that have taken a battering from the wet Irish winters, and overseeding is often the first thing we recommend.
In this guide, we will walk you through everything you need to know about overseeding your lawn in Ireland — from the best time of year to do it, to choosing the right seed, preparing your soil, and looking after the new grass once it starts to come through.
What Is Overseeding?
Overseeding simply means spreading new grass seed over your existing lawn without tearing up the turf or soil underneath. The idea is to fill in thin spots, thicken up the overall coverage, and introduce fresh, healthy grass plants into your lawn.
Over time, even well-maintained lawns naturally thin out. Grass plants have a lifespan, and factors like foot traffic, shade, drought, disease, and moss can all take their toll. Overseeding introduces new, vigorous grass plants that help your lawn look fuller, greener, and more resilient.
It is not the same as reseeding, which involves stripping back the lawn and starting from scratch. Overseeding works with what you already have and builds on it.
When Is the Best Time to Overseed in Ireland?
Timing is everything with overseeding. Get it right and you will see results within a few weeks. Get it wrong and you could be wasting good seed.
Autumn — The Ideal Window
September to mid-October is the sweet spot for overseeding in Ireland. The soil is still warm from summer, which helps with germination, but the air is cooler and we tend to get regular rainfall. This combination is perfect for new grass seed. The young seedlings also have the whole autumn and mild early winter to establish their root systems before the cold really sets in.
Spring — A Good Second Choice
If you missed the autumn window, April to May is your next best option. The soil is warming up again and daylight hours are increasing, which encourages growth. The risk with spring overseeding is that a dry spell in May or June could stress the new seedlings before they are properly established. You may need to water more frequently if the rain does not cooperate.
Avoid Summer and Deep Winter
Mid-summer is too hot and dry for reliable germination, and winter is too cold. The seed may sit dormant or rot in waterlogged soil. Stick to autumn or spring for the best results.
How to Prepare Your Lawn for Overseeding
Good preparation is half the battle. Throwing seed onto an unprepared lawn is a waste of time and money. Here is what you need to do before you start.
Step 1: Mow the Lawn Short
Cut the grass shorter than you normally would — down to about 25mm (1 inch). This lets light reach the soil surface and gives the new seed the best chance of making contact with the ground. Collect the clippings rather than leaving them on the lawn.
Step 2: Scarify the Lawn
This is a crucial step that a lot of people skip. Scarifying removes the layer of dead grass, moss, and thatch that builds up on the surface of your lawn. If this layer is too thick, new seed will sit on top of it instead of reaching the soil. A spring-tine rake will do the job on a small lawn, but for larger areas, a powered scarifier makes life much easier.
We have a full guide on scarifying your lawn if you want to go into more detail on this step.
Step 3: Aerate the Soil
If your soil is compacted — and most Irish lawns are to some degree, especially heavy clay soils — aerating will help enormously. You can use a garden fork to spike holes across the lawn, or hire a hollow-tine aerator for better results. Aeration allows air, water, and nutrients to reach the root zone, giving new seedlings the best start.
Step 4: Apply a Top Dressing
Spreading a thin layer of top dressing (a mix of loam, sand, and compost) over the lawn after scarifying and aerating creates a lovely seed bed for the new grass. It fills in minor hollows, improves drainage, and gives the seed something nutritious to germinate into.
Have a look at our top dressing guide for more on how to get this right.
Step 5: Spread the Seed
Use a broadcast spreader for even coverage on larger lawns, or spread by hand on smaller areas. The general rule of thumb is around 25-35 grams per square metre for overseeding (this is lower than the rate for a brand new lawn). Try to spread the seed in two passes at right angles to each other to avoid stripes or gaps.
Step 6: Lightly Rake and Water
Gently rake the seed into the surface so it makes good contact with the soil. Then give the whole area a thorough but gentle watering. You want the soil moist, not flooded.
Choosing the Right Grass Seed for Overseeding
The seed you choose matters. For most Irish lawns, a mix that contains perennial ryegrass is your best bet. Ryegrass germinates quickly (often within 7-14 days), establishes fast, and handles our wet climate very well.
If your lawn has shaded areas under trees or along north-facing walls, look for a mix that includes fine fescue varieties. These are much more shade-tolerant than ryegrass.
For hard-wearing family lawns where children and dogs are running around, a mix with a higher proportion of ryegrass will hold up better under heavy foot traffic.
Buy the best quality seed you can afford. Cheaper mixes often contain a high proportion of annual meadow grass, which looks fine initially but dies off after a year, leaving you back where you started.
Aftercare — Looking After Your New Grass
Once the seed is down, the work is not over. The next few weeks are critical.
Watering
Keep the soil consistently moist for the first two to three weeks. In Ireland, autumn rainfall often takes care of this, but if we get a dry spell, you will need to water lightly once or twice a day. Do not soak the lawn — light and frequent is the approach.
First Mow
Wait until the new grass is at least 50-60mm (2-2.5 inches) tall before you mow for the first time. Set the mower on a high setting and only take off the top third. Be gentle — the new grass plants are still establishing their roots and a heavy mow can pull them out of the ground.
Feeding
Apply a light autumn lawn feed about three to four weeks after overseeding. This provides the nutrients the young grass needs to establish strong roots heading into winter. Avoid high-nitrogen summer feeds at this stage as they promote leafy top growth at the expense of root development.
Keep Off the Grass
Try to keep foot traffic to a minimum for at least four to six weeks after overseeding. The new seedlings need time to root in properly, and heavy traffic can damage or kill them before they get established.
Frequently Asked Questions
How long does it take for overseeded grass to grow?
Most grass seed mixes used in Ireland will start to germinate within 7 to 14 days, depending on soil temperature and moisture. You should see a noticeable improvement in your lawn within four to six weeks. Full establishment typically takes two to three months.
Can I overseed without scarifying first?
You can, but results will be much poorer. The thatch layer on most lawns prevents seed from reaching the soil. Scarifying gives the seed proper soil contact, which is essential for germination. We always recommend scarifying before overseeding.
How often should I overseed my lawn?
For most lawns in Ireland, overseeding every one to two years is enough to keep the grass thick and healthy. If your lawn sees particularly heavy use or has persistent thin patches, annual overseeding in autumn will keep on top of things.
Do I need to cover the seed after spreading?
A light top dressing or gentle raking is usually sufficient. You do not need to cover the seed with a thick layer of soil. A thin covering helps retain moisture and protects the seed from birds, but too much will prevent it from germinating.
Need a Hand With Your Lawn?
If overseeding sounds like a lot of work, or if your lawn needs more attention than a simple overseed, give us a shout. Seamus and Pete have over 35 years of experience looking after lawns and gardens across Dundalk and County Louth. Whether you need a full lawn renovation, regular grass cutting, or just a bit of advice, we are happy to help.
Call us on 085 168 5170 for a free quote or to have a chat about what your lawn needs.
