How to Top Dress a Lawn

Top dressing a lawn means spreading a thin layer of sandy soil over the grass and brushing it down between the blades. It fills the hollows so the lawn mows flat, and it puts better soil around the roots. In Perth, do it in late spring or early summer. Mow short first, core the lawn if it is compacted, and never spread more than 10mm at once.

What top dressing does for a lawn

A top dressing is a thin layer of soil or sand spread over an established lawn. The grass grows up through it, so the level of the lawn rises a little each time and the low spots fill in. Done over a season or two, it takes the bumps out of a lawn without lifting it and laying new turf.

• •It levels the surface. Dressing settles into hollows, dips and old trench lines, so the mower stops scalping the high spots.
• •It improves the soil the roots grow in. A dressing with loam and manure through it holds more water and feed than the bare sand most Perth lawns sit on.
• •It thickens the lawn. The runners of buffalo, couch and kikuyu grow up through the dressing and root into it, which fills thin patches.
• •It helps with thatch, the layer of dead stems and runners that builds up between the grass and the soil. A sandy dressing worked into it helps it break down.

What it will not do is fix a lawn that is dying for another reason. If water sits on top and beads instead of soaking in, the soil has gone water-repellent, and that needs fixing first. Step 3 of the method covers it.

When to top dress a lawn in Perth

Top dress when the grass is growing strongly, so it can push up through the new layer within a couple of weeks. Most Perth lawns are warm-season grasses, meaning buffalo, couch and kikuyu, which grow hardest in the warm months and slow right down in winter. Lawn Solutions Australia put the best window at late spring to early summer, and for Perth that means roughly October to December.

Avoid winter. A dressing spread on a lawn that has stopped growing just sits there, and the grass under it can yellow before it recovers. Avoid the hottest weeks of January and February too, when a freshly dressed lawn dries out fast on a watering roster.

What you need

• •The dressing itself. Special Lawn Mix or Lawn Sand, see the next section for which.
• •A mower, set lower than usual for the day.
• •A wheelbarrow and a shovel.
• •A levelling rake, a wide flat rake built for spreading dressing, or a stiff yard broom if you do not have one.
• •A hollow-tine aerator if the lawn is compacted. It pulls out small plugs of soil, and you can hire one from most hire shops.
• •A hose or sprinklers for watering it in.

Special Lawn Mix or Lawn Sand?

We sell two dressings for lawns, and they do slightly different jobs.

Special Lawn Mix is top dressing sand blended with Gingin loam and poultry manure, made to Australian Standard AS 4419. The sand lets it brush in and level, the loam helps it hold moisture near the roots, and the manure feeds the lawn. Use it when the lawn is thin, patchy or tired as well as bumpy, which describes most Perth lawns growing in plain sand.

Lawn Sand is a fine sand on its own. It levels and improves surface drainage but does not feed. Use it when the lawn is healthy and only the surface is uneven, or where water pools in a low corner after rain.

Laying new turf instead? Use Special Lawn Mix, spread at least 50mm deep under the rolls.

How to top dress a lawn, step by step

1. Mow short

Mow a notch or two lower than usual and catch the clippings. A short lawn lets the dressing reach the soil instead of sitting on the leaves. Do not scalp it down to bare runners, just shorter than normal.

2. Core the lawn if it is compacted

Coring, also called core aeration, means pulling small plugs of soil out of the lawn with a hollow-tine aerator. It lets air, water and dressing into ground packed hard by foot traffic. Lawn Solutions Australia recommend it before top dressing. Leave the plugs on the surface to dry, then break them up with the rake. The dressing will fill the holes.

If the lawn is soft underfoot and water soaks straight in, you can skip this step.

3. Check the water soaks in

Turn the sprinkler on for a few minutes and watch. If the water beads and runs off instead of soaking in, the sand has gone water-repellent, which is common in Perth. Treat it with a soil wetter first and water it in. Otherwise the dressing sits on dry, repellent sand and the lawn does not improve.

4. Tip small piles across the lawn

Barrow the dressing out and tip it in small piles spread across the lawn, rather than one big heap. Small piles are far easier to spread thin.

5. Spread it no more than 10mm deep

Spread each pile out with the back of the levelling rake. Lawn Solutions Australia advise never putting down more than 1cm in one application, and keeping the tips of the grass showing through. Five to ten millimetres is right for most lawns. A thicker layer blocks the light and smothers the grass you are trying to help.

Deep hollows need more than 10mm to fill. Do them in stages: dress, let the grass grow through, then dress again a few weeks later.

6. Work it down into the grass

Drag the rake or broom back and forth until the dressing has dropped down between the blades and the grass is standing up through it. What ends up in the low spots is what does the levelling. If you can see a solid layer of soil on top, spread it further.

7. Water it in

Water thoroughly straight away. That settles the dressing into the lawn and, with Special Lawn Mix, starts the manure feeding. Keep the lawn moist over the next couple of weeks while the grass grows through, within your watering days.

8. Leave it to grow through

Hold off mowing for a week or two, until the grass has grown clear of the dressing. Then mow at your normal height.

How much top dressing do I need?

Multiply the area of the lawn in square metres by the depth in metres. At 5mm that is area × 0.005, at 10mm it is area × 0.01. So a 100m² lawn takes 0.5m³ at 5mm and 1m³ at 10mm. The soil calculator does the sum for you if you enter the length, width and depth.

Then round to what our loader scoops. One scoop is about 0.33m³, three scoops make a cubic metre, and a scoop and a half is 0.5m³. If your sum comes out at 0.42m³, order 0.5m³.

• •50m² lawn at 5mm: 0.25m³, order a scoop, about 0.33m³.
• •85m² lawn at 5mm: about 0.42m³, order 0.5m³.
• •100m² lawn at 10mm: 1m³, three scoops.
• •150m² lawn at 10mm: 1.5m³, four and a half scoops.

Up to 0.5m³ is half a trailer load, 0.6m³ is about two thirds, and 0.7m³ fills a trailer. If you are collecting, we lend trailers free for two hours. Larger amounts can be delivered across Perth's southern suburbs by truck.

Common mistakes

• •Spreading it too thick. More than 10mm at once smothers the grass. Do deep hollows in stages.
• •Dressing in winter. The grass cannot grow through it until spring, and the lawn can yellow underneath.
• •Using garden soil. A rich bed mix sits on top of the grass as a mat. A lawn dressing has to be sandy so it brushes in.
• •Skipping the water check. Dressing over water-repellent sand buries the problem instead of fixing it.
• •Not watering in. A dry dressing blows around and does not settle into the hollows.

Frequently asked questions

Can I top dress straight after coring?

Yes, and it is the best time to do it. The holes left by coring fill with dressing, which gets better soil down into the root zone. Let the plugs dry, break them up, then spread the dressing.

How often should I top dress?

Once a year in late spring is plenty for most home lawns. A lawn with deep hollows can take a second, lighter dressing a few weeks after the first.

Should I fertilise as well?

Special Lawn Mix has poultry manure in it, so it feeds as it goes on. Lawn Sand does not feed, so if you use it, spread a lawn fertiliser a week or two later.

Can I top dress buffalo grass?

Yes. Buffalo, couch and kikuyu all spread by runners and grow up through a dressing well. Mow short first, as buffalo leaves are broad and hold the dressing up if the lawn is long.

Not sure which dressing your lawn needs, or how much? Bring the size of the lawn to the yard in Bibra Lake, open seven days, and we will work it out with you.