G’day, Nikolai here from The Lawn Firm. If your lawn feels spongy, looks dull, or dries out fast, thatch is likely the cause. Thatch is a tight layer of dead stems and roots that sits on top of the soil. It blocks water, air, and nutrients. In Canberra’s clay soils, thatch makes dry patch and pest damage worse. Here’s my simple plan to remove it and get your grass growing strong again.

What is thatch?

Thatch is organic build-up between the green leaf and the soil. A thin layer is normal. A thick layer (more than 1–1.5 cm) is a problem. It stops water from soaking in. It traps fertiliser above the root zone. It gives pests and disease an easy home.

Signs your lawn needs dethatching

A spongy feel underfoot
Brown thatch layer you can see when you part the grass
Scalping even at normal mowing height
Water run-off or fast dry-out after watering
Patchy colour that does not respond to fertilising

Best time to dethatch in Canberra

Early autumn (March–April): My first choice. Warm soil, cooler days, steady recovery.
Spring (late Aug–Oct): Also works well as growth kicks back in.
(Avoid deep winter and peak summer heat)

Tools that work

Dethatching mower (scarifier): Blades slice and lift thatch.
Verti-mower: For heavier build-ups.
Metal rake: Handy for very small areas and clean-up.

My step-by-step dethatching process

Mow lower than usual. Collect clippings.
Set blade depth. Aim to reach the thatch layer, not the soil.
Run in one direction. Work slowly so the blades can lift debris.
Run a second pass at 90°. Only if thatch is thick.
Rake and remove debris. Get everything off the surface.
Core aerate (ideal). Open the soil to help recovery and water movement.
Top dress lightly (5–8 mm). Use fine sandy loam to level and improve contact.
Overseed thin areas. Seed locks into the fresh surface and fills gaps.
Water well. Settle the top dress and support new shoots.
Fertilise lightly. Use a gentle, slow-release feed to support roots.

How low should you go?

Remove the thatch. Do not scalp the crown. If you see lots of bare soil, you have gone too deep. It is better to do two lighter passes than one aggressive cut.

Aftercare that speeds recovery

Water deeply, not often. Keep the profile moist for two weeks, then shift to deep soaks.
Resume mowing once new growth reaches 5–6 cm. Take off only one-third of the leaf.
Add a wetting agent if the soil is hydrophobic.
Stay on a fertilising schedule matched to the season.

Common mistakes I fix

Aggressive settings that rip out runners and leave bare soil.
Skipping clean-up, which smothers new shoots.
No aeration, so recovery stalls in compacted clay.
Heavy top dressing that buries the leaf.
Dethatching at the wrong time, which slows regrowth.

How often should you dethatch?

For most Canberra lawns, every 1–2 years is enough. High-traffic or fast-growing lawns may need light dethatching more often. If you keep mowing height consistent and feed correctly, you will need it less.

DIY or call The Lawn Firm?

You can tackle a small area yourself. For full-yard results, settings and sequencing matter. I assess the site, choose the right depth, and line up dethatching, aeration, top dressing, overseeding, wetting agent, and fertilising in one simple plan. That means faster recovery and fewer re-works.