Topdressing and Overseeding

Why overseed a lawn?

Grass doesn’t live forever. Individual grass plants only last a few years, and wear, shade, dry summers and pets all take more of them out along the way. If fresh grass isn’t coming through, the lawn slowly gets older, thinner and weaker, and moss and weeds are quick to claim the space.

Overseeding is sowing new seed into the lawn you already have, and it’s one of the best things you can do for it:

• Thickens thin and patchy areas before moss and weeds move in
• Keeps the lawn young. New plants are stronger, greener and more vigorous
• Introduces better grass varieties than the lawn started with
• Builds the kind of density that copes with wear, drought and disease

Why add topdressing over the seed?

Seed scattered on top of a lawn mostly goes nowhere, or feeds the birds. To germinate, seed needs to touch soil and stay damp. That’s exactly the job topdressing does:

• Tucks the seed in against the soil, the seed-to-soil contact everything depends on
• Holds moisture around the seed while it germinates
• Hides it from the birds
• Smooths out small dips and bumps while we’re at it
• Improves the soil your lawn is rooted in, year on year

Two jobs, one visit. The topdressing gives the seed its best possible start, and the new grass knits the topdressing into the lawn. It’s also the same job greenkeepers do on golf greens, and a big part of why greens feel so smooth and firm underfoot.

Why we use screened, bagged topsoil and compost

The material matters as much as the method. When we topdress, we use screened topsoil or compost that comes in sealed bags, not loose bulk bags.

Screened means the material has been passed through a fine mesh. No stones, no lumps of clay, no roots, and far less weed seed. It spreads evenly, works down into the grass properly, and gives the seed a clean bed to get going in.

Bulk bags are cheaper by volume, and that’s the honest trade-off. But loose bulk material is variable. You get stones that catch the mower, lumps that smother the grass, and weed seed you can end up fighting for years. It also sits out in the weather, and wet material spreads in clods rather than an even layer.

Bagged screened material costs more per square metre. We think it’s the wrong place to save money though. Topdressing goes straight into the surface of your lawn, and cheap material puts problems in that cost far more to get back out.

When is the best time?

There’s a small window in spring to overseed and topdress, once the frosts have passed. That window seems to get smaller each year though, as May is increasingly turning very dry. We can still do it in spring, if you’re prepared to water the lawn.

Late August, September and October are the best times. It’s generally damper, and the soil is still warm from summer, which is exactly what new seed wants.

Aftercare: the bit that decides everything

The first few weeks after seeding make or break the job. The seed needs kept damp, the new grass needs left alone while it establishes, and the first cuts need to be high and gentle. Once the new grass has been mown a couple of times, feeding takes over, and that’s already built into your seasonal programme.