When to overseed lawn: best time and correct approach

Why overseeding is essential for a thick lawn

Every lawn develops bare patches. Foot and play traffic, disease, drought, weed removal - all punches holes in your grass mat. A lawn with many bare patches looks poor, and worse: bare soil is the first thing weeds colonize. It is much easier to restore grass to bare patches than to dig weeds out later.

Overseeding is simple: you scatter new grass seed on bare and thin areas. After two to three weeks the grass shoots sprout, and six weeks later you have a fuller lawn. This is much cheaper than rebuilding, and it works fast.

Best time: autumn is ideal, spring also good

The best time to overseed is late August through late September. This is the ideal window. Why? The soil is still warm from summer, rain begins falling regularly, and young grass shoots have five full months of growth before winter arrives. A grass shoot that germinates in September is already mature and strong by April and May.

Spring (April-May) can also work, but is less ideal. The soil is cold, grass shoots grow more slowly, and by June it becomes warm and dry. Young shoots burn easily in heat.

October-November is too late. Grass shoots grow very slowly, frost can damage seed, and rain washes much away.

Preparation: four days of work

Day 1: Mow short and rake

Mow your lawn to 2-3 cm. This is shorter than normal. Then rake your entire lawn (bare and thick patches both). You want dead moss, leaves, and dead grass shoots removed. This "thatch" prevents seed from contacting soil.

Day 2: Fill ruts and holes

Have deep foot-ruts or hollows? Fill these with garden compost or seed-bearing sand (seed + sand mixed). This gives seed stability and nutrition.

Day 3: Scatter seed

Spread your grass seed evenly. This is tricky by hand. Better: use a grass seeding machine (cart). These cost 15-25 euros per day rental. Ensure every square metre gets the same amount of seed - usually 30-40 grams per m2.

Do not roll immediately after seeding - wait three weeks. The seed must first germinate. Rolling damages young shoots.

Day 4: Water and wait

Directly after seeding you water the seed thoroughly wet (5-10 mm). The next two weeks: water lightly daily if no rain falls. Grass shoots need moisture to germinate, but waterlogging causes rot.

Step-by-step

Step 1: Decide your overseeding strategy

Is your entire lawn thin? Then overseed all of it. Are there only patches? Then concentrate on those areas. Larger bare spots (larger than 30 cm square) may be better rebuilt.

Step 2: Choose your grass seed type

Use the same grass species as your current lawn. Your supplier can help you match. Mix of perennial ryegrass and red fescue is standard. For shaded patches: more red fescue. For full sun: more ryegrass.

Step 3: Mow and rake well

Mow to 2-3 cm, then rake aggressively. This is annoying but crucial. You want thatch gone and seed in contact with soil.

Step 4: Scatter seed

Use a seeding machine. Scatter in two directions (North-South, then East-West) so your coverage is certain.

Step 5: Water first two weeks

Light water each day - enough to keep soil moist, not muddy. After two weeks it can dry out.

Step 6: Mow carefully after 6 weeks

When new grass is 5-7 cm tall, you may mow. Do it carefully at 3-4 cm. Not shorter - young grass is weak.

Frequently asked questions

How much seed per square metre?

Standard 30-40 grams per m2. Check your seed package - it indicates how much you need. For very thin areas 50 grams per m2 does no harm.

Which grass seed brand is best?

German brands (Feldsaaten, Barenbrug) and Dutch (Consta, Barenbrug NL) are reliable. Avoid very cheap seed of unknown brand - lots of weeds and other grasses in it.

Can I overseed in drought?

No. Seed without water does not germinate. Wait for rain, or ensure you can water daily.

Does rolling after seeding help?

No, it is harmful. Rolling compacts soil and damages germinating seed. Let it first three weeks.

Why does my overseeded grass not grow?

Usually: thatch on seed (raking insufficient). Or: no water (seed dries out). Or: seed is old (check expiration date). Or: wrong grass type for your climate.

Discover your perfect garden design

At gardenworld.app you can upload your front yard and see how lawn develops through the year - including overseeded areas that fill in. Plan now what your lawn can be come October.