Fixing the 'Spongy' Lawn: Why Kikuyu Needs Tough Love (and Better Edging)

The Scenario

A homeowner recently asked:

I hired someone to scarify and top dress my spongy, uneven Kikuyu lawn, but two weeks later it's growing back unevenly. I've broken sprinklers in the past and I'm worried I'm messing up the recovery.

The GardenOwl Diagnosis

The Assessment

You have a Kikuyu lawn that felt like walking on a cheap mattress—spongy, dense, and uneven. This issue not only ruins your curb appeal but is a textbook example of The Spongy Thatch Trap. You did the right thing: you hired a pro to scarify (rip out the thatch) and top dress (level it with soil). But now, you are staring at a backyard that looks like the surface of Mars, or perhaps a patchy green quilt, and you are panicking. You admit you’ve broken sprinklers before and haven’t been consistent with mowing. You are wondering if you’ve ruined it or if this mess is part of the process.

The Trap

The trap here is misunderstanding the beast that is Kikuyu grass. It gets "spongy" because of thatch buildup. Kikuyu grows via vigorous runners (rhizomes and stolons). If you don't mow it low and often, those runners stack on top of each other, creating a thick, floating mat of grass that separates the green blades from the soil.

When you finally scalp it or top dress it, it looks horrific. That is the trap: thinking you killed it. You didn't. Kikuyu is nearly indestructible. The real mistake is what happens next. If you don't install proper barriers now, while the ground is exposed, those runners are going to dive underground and invade every garden bed, shed corner, and retaining wall in sight.

The Solution (Deep Dive)

Recovering from a top dress is a waiting game, but you have work to do while the grass wakes up.

1. Water is Non-Negotiable

You mentioned running over sprinklers. Fix them. Immediately. Top dressing adds a layer of soil that can bake hard in the sun. If the rhizomes underneath dry out, they die. You need consistent moisture to push the new green growth up through that red dirt. If you are in a sandy zone, check out my guide on irrigation setups for sandy soil to understand why spray coverage matters.

2. Install "Real" Edging

This is where most homeowners fail with Kikuyu. That runner battle is real. Kikuyu laughs at those flimsy plastic edging strips you buy at the hardware store. It will tunnel right under them.

The Fix: You need a deep physical barrier. Whoever puts in your new garden beds needs to install concrete curbing or heavy-gauge metal edging sunk at least 6 inches (150mm) into the ground. Without this, you will be pulling grass out of your mulch for the rest of your life. If you are dealing with a slope near that retaining wall, read up on managing slopes without breaking your wall.

3. Protect the Retaining Wall

I see a lot of red soil pushed right up against that back retaining wall and metal fence. Be very careful here.

• Don't block the weep holes: Those little holes in the wall let water escape. If you bury them with topsoil, the water builds up pressure behind the wall, which can cause structural failure.
• Watch the fence: Piling soil against metal fence posts promotes rust. Pull the soil back slightly or use gravel against the metal.

4. The "No-Mow" Shed Zone

Mowing tight corners around a square shed is a nightmare. You end up weed-whacking the paint off the metal.

The Fix: Don't grow grass there. Take the grass out for a veggie patch or a gravel service area. I recently designed a similar layout where we transitioned from lawn to gravel about 2 feet out from the shed. This keeps your mower away from the structure and gives you a clean, weed-free zone. If you are worried about the gravel migrating into the grass, you need to install the edging properly.

Visualizing the Result

Imagine this: instead of a spongy, ankle-twisting mess, you have a tight, firm green surface that feels like a putting green. The transition from your lawn to the shed is crisp—no shaggy grass creeping up the metal siding. You can mow the whole yard without stopping to hand-pull runners out of your tomato plants because that 6-inch metal barrier is doing its job. This is the difference between a "yard" and a "landscape."

If you want to test this on your own yard, upload a photo to our Exterior Design App and see what this design would look like in your space.