Lawn Renovations
What, why, when and how
After a winter where your lawn may have become drab, shabby and lifeless (apart from the knee-high weeds), Spring is
the perfect time for renovating your lawn.
But what does a lawn renovation involve? How does it help? Here's an explanation.
Renovating your house refreshes it; gives it a fresh lease of life, and sometimes involves structural changes. It’s the
same with renovating your lawn. Over time lawns can deteriorate too, for various reasons.
Let’s look at common issues and processes, and how a renovation can help your lawn.
Thatch
One common issue is the accumulation of organic matter on the soil surface. Some of it does break down and adds
nutrition to the soil. However some of it accumulates quicker than it breaks down, so over time it forms a dense layer on
the soil surface. This is called 'thatch'. See the images below.
Thatch acts like a dense sponge, absorbing water, air and nutrients, and prevents them from entering the soil. The
problem with this is the turf roots stay in this shallow layer, because that's where all the goodness stays - there's no
incentive for the roots to grow deeper. During hot weather, the thatch layer can dry out quickly, leaving all the turf roots to
dry out also, harming your lawn. You'll be forever watering your lawn trying to keep it alive.
Turf roots need to grow deeper into the ground where more stable moisture, temperature and nutrient levels can be
accessed during hot, stressful conditions. So, thatch needs to be removed using a scarifier - a mower with vertical
blades. Mowing low with a standard rotary mower can also achieve this to an extent - how low you should mow depends
on your turf variety. See the notes below for more info.
If your turf is thin and patchy, and soil is clearly visible through the turf, you could skip the scarifying process in your reno.
Thatch is unlikely to be present, and your turf wont need thinning out.
If, however, your turf is too thick and spongy, scarifying is great for thinning it out. Sometimes turf can grow too well, and
become very difficult to mow, with the blades “grabbing” the turf and leaving a yellowish scalped appearance. Again, how
low you go with the vertical blades of the scarifier depends on your turf variety. See notes below.
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© 2020 Greg Hamilton, Grass by Greg. Contents must not be copied, in part or full, without permission from writer.
Soil Compaction
Over time soil can become compacted, which can also prevent water, air and nutrients entering the soil. So, core aeration
is needed to remove plugs of soil to relieve the compaction. Core aeration also penetrates and removes the thatch layer,
giving excellent access to the soil below.
With deeper water and nutrient penetration into the soil, the roots will grow deeper into the soil in search for them. This
results in a deeper, more robust root system, and therefore a healthier and more resilient lawn. With more air entering the
soil, turf roots can take in vital oxygen, and microorganisms can do their thing to break down organic matter and release
nutrients for the turf to consume.
What should we do with the soil cores taken out of the ground? If the soil is good quality, keep them – they can be rubbed
back into the turf with a screed, or mulched using a mower. If the soil is poor quality, such as high clay content, then rake
them up to collect and remove them.
Soil pH
With thousands of holes punched into your soil, it provides an excellent opportunity to further improve your soil for the
growing season ahead. It's a perfect time for a soil pH test - very quick and easy to do. Test kits are cheap and very easy
to use - instructions within will tell you what do based on your test results.. If your soil pH needs adjusting, sulphur or lime
can be applied, which then gets incorporated into the soil via the core holes.
Soil with a neutral pH is very important - if the soil is too acidic or too alkaline, important nutrients will be bound to the soil,
and not released for the turf to use. The nutritional needs of your lawn wont be met, and it wont reach its potential. Your
lawn needs a balanced diet too.
Grab a few cores from various parts of your lawn, and break off the lower section of each. Mix the soil together and
perform the test. If your lawn is very large, or you have multiple lawns, then do multiple tests of samples taken from
various areas/lawns. If your soil pH needs adjusting, sulphur or lime can be applied, which then gets incorporated into the
soil via the core holes.
Other goodies to apply
Another commonly-used amendment at this time is gypsum to help break up clay. It too enters the core holes and does
its thing more effectively.
A renovation can be very stressful on turf, so a feed of fertiliser 2-weeks beforehand would give it a good boost in
preparation. Something like 2Spec Establish is great – it contains 15% Nitrogen (N) for excellent leaf growth, 10%
Phosphorus (P) for root recovery and new root growth, and 10% Potassium (K) for strength and resilience. It’s ideal for
turf bouncing back from winter dormancy, and gives it a boost during renovation and beyond.
Other excellent products to apply at this time include:

Humic acid (improves soil structure, quality), eg Andersons HUMIC DG Greens Grade

Wetting agents (improves water infiltration and retention), eg Hydrolink Advance

Seaweed/kelp products (excellent for root development, stress recovery, overall turf health and soil quality), eg
Fertech Kelpro or Fertech Stimulus.
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© 2020 Greg Hamilton, Grass by Greg. Contents must not be copied, in part or full, without permission from writer.
Topdressing
Topdressing serves two main purposes – to improve your soil structure, and to level out low spots. Which material you
use depends on your reason for topdressing.
If your soil is already in good condition, with minimal improvement needed, then topdressing with sand is the common
approach. Sand will fill those core aeration holes and provide thousands of long-lasting avenues for the good stuff to
enter the soil. These sand-filled holes also help with draining excess surface water away, helping to prevent fungal
diseases. Sand is also better for levelling low spots, as the sharp edges on the particles helps it to retain levels better.
If your soil is in poor condition, and needs improvement, a sandy-loam soil is more appropriate to use. You get the
benefits of sand, but also the added benefit of some organic material entering the core holes and improving the soil as it
breaks down. Low spots can still be filled, however there may be a little more settlement occur than with sand.
Generally a depth of 10mm of topdressing is used to calculate how much is needed eg 100m² x 10mm depth = 1m³ of
topdressing. When topdressing, it's best to not bury the turf - 10mm is enough to allow some leaf to show through. Or, if
you've fully scalped your lawn down to soil, 10mm depth of sand will allow new growth to push through. Little and often is
the best approach to use.
Timing
Renovations should take place only after a lawn has had at least 12 months to establish.
So, you've decided your lawn needs a reno to improve it. Or you want to do a reno to prevent issues from arising. When
do you know its the right time to do it?
When it has begun actively growing in Spring.
This will be at different times of the year, depending where you live and your local conditions. Just because
Queenslanders have done their reno's in early Spring and are marvelling at the results, it doesn't mean it’s time for those
in the southern states to get stuck into it. There's no advantage in doing reno's early - it won’t trigger your lawn into
growing sooner - only warm weather will do that (higher soil temperatures). If anything, a premature reno may set your
lawn back a little, as it may not have the required energy to recover. When you have started mowing regularly again, then
you can safely do a reno.
Notes for different turf varieties
Buffalo-owners please note - you should not mow or scarify any lower than ~25mm above soil level. A scarifier set at this
height will help thin out a buffalo lawn (technically called 'vertimowing' - mowing with vertical blades), but never, ever go
any lower than ~25mm. This is because the bulk of the Buffalo's critical "infrastructure" is above ground - you need to
keep that!
Couch (including TifTuf), kikuyu and zoysia owners, you can mow and/or scarify as low as you like on established lawns,
even down to dirt if you are really keen. This is because these varieties have large rhizome networks - under-ground
runners, which will regenerate by sprouting new surface growth. This is how it invades garden beds etc.
Zoysia owners please note - recovery from a low scalp will be very slow, and the appearance of your lawn will be
compromised for many weeks. To keep up appearances, scarifying instead of scalping will remove thatch whilst also
retaining much of the green growth. Couch and kikuyu varieties bounce back quite quickly by comparison.
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© 2020 Greg Hamilton, Grass by Greg. Contents must not be copied, in part or full, without permission from writer.
Cool season grasses such as rye, bent and fescue can also be renovated, typically done in Autumn. Scalping down to
dirt is NOT advised as a substitute for scarifying cool-season grasses, as they may not recover. A low mow combined
with scarifying is best. Coring and scarifying does remove some grass which wont regenerate. However the process can
be followed up with oversowing of seed - the renovation process creates an excellent seed bed for new seed to settle into
and germinate.
Scarifying v Scalping
Scalping (mowing very low) is a poor substitute for scarifying, as horizontal blades don't penetrate into the thatch layer as
well as vertical scarifier blades do. If scalping to remove thatch, it has to be set very low, as low as the mower can go
(and even then it may not be low enough to remove the thatch layer). This would remove all the green material from your
lawn, compromising its appearance. Whereas, with scarifying, the low mow doesn't have to be as low. The scarifier
blades can still penetrate the turf and thatch when the turf is cut to ~10mm or so. Some green leaves can be left on the
turf, making it look better after the reno is done. Plus with green leaves showing, photosynthesis can take place, enabling
the turf to develop the energy it needs to grow and recover more quickly. Note the mowing and vertimowing
considerations for Buffalo and cool-season turf varieties above!
The process:
1. Fertilise your lawn 2 weeks prior to reno
2. Apply soil wetter 2 days prior to reno, water your lawn thoroughly (helps coring machine to penetrate soil)
3. Flag any popup sprinklers and any shallow pipes
4. Scalp (or low mow for Buffalo & cool-season grasses)
5. Scarify (or vertimow for Buffalo & cool-season grasses)
6. Collect debris (rake it up, or mow with the catcher on)
7. Core the lawn
8. Collect cores if soil is of poor quality, or leave the cores if good quality soil
9. Test soil pH
10. Add pH amendments if required
11. Apply other lawn amendments (eg gypsum, humic acid, soil wetter, kelp products)
12. Apply topdressing
13. Level topdressing with a screed (this will also rub in any remaining cores into the topdressing)
14. Water thoroughly
15. Enjoy a beverage after some hard work
16. Apply a soil wetter 1-2 weeks after topdressing. Sometimes applied sands/soils can become hyrdophobic after
topdressing.
These are all common aspects of a lawn renovation, and is usually done at the start of the growing season so the lawn
can recover and become nice and healthy. Renovating a lawn can seem harsh and daunting to do – the common phrase
“being cruel to be kind” certainly applies here. But the "before and after" results can be amazing.
You will need lots of bins or a big trailer - the amount of debris created during a reno can be insane.
Good luck!
Disclaimer: The information contained within this document is written for the purpose of assisting domestic lawn
owners with renovating their lawns. Readers are encouraged to seek further information, education and
confirmation on the topics and information contained within prior to conducting works on their lawns. The writer
accepts no responsibility for injury or damages arising from recommendations made within this document.
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© 2020 Greg Hamilton, Grass by Greg. Contents must not be copied, in part or full, without permission from writer.