When is the best time to scarify a lawn?

Scarifying is a very beneficial lawn treatment and rather than being considered as a remedial maintenance exercise every one to two years, you should consider scarifying as a regular maintenance procedure.

What does scarifying do?

During the course of a season dead grass (called thatch) and lateral grass stems build up, thus restricting light and air getting through to the grass roots.

As thatch builds it restricts any desired grass and instead moss and weeds are encouraged to take over, leading to a downward spiral in the health of a lawn.

A scarifier is in effect a vertical mower with knife blades (or wire tines) spaced out along a reel - much like a cylinder on a mower.

These vertical blades act like a vigorous comb, forcing out any build up of rubbish at grass root level.

These blades can be lowered, or raised, to combat the depth of thatch, or in some applications, penetrate into any crusty soil layer.

The deeper the blades go, and the more extreme and vigorous the action is on the roots, potentially the more beneficial this remedial action has on grass grass root zone.

A deep incision into the soil cuts through any shallow grass roots, which in stimulates tillering - tillering occurs when the grass sends out new shoots where a root has been pruned.

If this procedure is practised on a regular basis this root pruning will encourage a thicker grass root zone and aid crowding-out of undesirable weeds whilst also discouraging moss.

A scarifier can be set just to brush the soil surface without any interference with the roots of the grass. This procedure is effective if you just want to remove a build up of dead grass or take out any unwanted lateral grass growth and is a normal - and especially beneficial - procedure during the active growing season.

,p.A light grooming is recommended at least once a month during active grass growth to deter any major build up of thatch and reduce the need for heavy remedial autumn/winter maintenance.

Modern professional mowing machinery is often fitted with a grooming reel set just behind the front roller. Every pass with the mower removes any loose detritus, thus keeping the surface aerated and free from build up of lateral grass growth and thatch.

What to do

Scarifying a lawn produces an awful lot of arisings and the whole process can be very time consuming so it's advisable to cut your grass at least three days before the scarifying. This will clean up the surface of any leaves and/or debris, such as leaves and twigs, as well as all of the excessive grass growth.

Cut the grass again on the day you want to scarify. This will help to remove excessive moisture and a further any growth of grass.

Scarifying will produce bundles of dead grass, so cutting first ensures that you are not having to labour through the normal vertical grass growth as well penetrate into the thatch and lateral grass.

Set the scarifier blades to the required height - if the lawn is dense and springy then an initial pass just into the surface will clear the way for a second, and lower, pass. If needed, make a third pass so that the scarifier's collection box isn't filled too quickly.

Repeat the process as many times as is needed, lowering the vertical cutting blades as you go, until you are satisfied that you have removed sufficient grass and thatch.

If thatch and rubbish is still coming out freely then continue until you are confident there is no more to be achieved.

It's recommended that every pass is made at 90 degrees from the previous one, this ensures that grass is lifted each time and maximised the efficiency of the machine.

Not every scarifier comes with a collection box which means that you may have to collect the grass by raking it up.

Rake up as much as possible by hand and then vacuum up any residual clippings with a rotary mowing machine.

As a result of thatch removal you may well find there are bare patches left. These bare patches need to be aerated, seeded and dressed to promote new grass.

Early autumn is the best time for a deep penetrating scarification and thorough clear out of moss and thatch. The soil is also at the best optimal temperature for grass seed germination.

Seeding in autumn also allows enough time for new seed to germinate and for the grass to establish itself well enough for one or two light cuts, with a rotary mower, before it passes into a semi-dormant state for over-wintering.

If you are carrying out any scarifying in the spring it is best to wait until the frosts have passed and the soil has warmed sufficiently so that the grass roots may recover sufficiently.

Hitting grass roots to hard and too early will shock the plant and cause it to suffer stress meaning that the lawn may take too long to recover before the summer heat.

Springtime and throughout the summer - only if conditions are favourable - is best for light to moderate scarification/grooming.

Do you need a scarifier? - Click here.

Comments

[dominic]

when is the best time to start scarifying the lawns

[Philip Voice]

Hi Dominic

Sorry for the late reply regarding your question.

You can scarify as soon as the grass starts to grow strongly.

It is also possible to groom the surface which is less vigorous and will just remove lateral growth and thatch without didturbing the roots.

[Robert Gisbon]

Once a lawn has been scarified, is there a requirement to treat the scarified area with a lawn 'tonic', fertilizer or simply water regularly in order to stimulate fresh growth?

Can I do this now or wait until the summer is over..?

Thanks for any helpful observations

RG

[Philip Voice]

Robert

Scarifying will stimulate both root and leaf blade growth so the addition of fertiliser is recommended.

However, it is still too early to scarify your lawn vigorously. I would normally time any treatments to start after the end of August and more often than not in the middle of September.

The soil will be warm and the days shorter and normally cooler and the chance of rain that will permeate through the soil is increased.

As far as fertiliser is concerned - Potash fertiliser is applied going into and through the winter to encourage root growth and recovery.

Nitrogen should be avoided unless it is a controlled release. Nitrogen will cause the leaf blade to grow to vigorously and any soft tissue is easily destroyed by frosts diminishing the potential for recovery .

[Richard Rixson]

I have a lot of moss in my lawn. Is it still acceptable to scarify now or should I leave it until next Spring ?

[Philip Voice]

Hi Richard

Yes it is OK but try to avoid being too vigorous and do not cut into the roots too deeply.

Just brushing the surface with the tines is ideal.

This time of year the soil should be radiating enough heat for grass roots to recover and for new grass seed to germinate.

Bear in mind that the air temperature could change very soon which will slow the recovery.

Be sure that leaves are not aloud to rest on your lawn surface for too long either.

[Ash Ainscough]

Hi,

I have applied Autumn Feed and Mosskiller and as expected the moss has blackened. Is it still ok to scarify the lawn this late in the year or should I leave it until Spring?

Thanks

[Philip Voice]

I am assuming that it was a combined moss killer and fertiliser.

I prefer to add iron in advance of scarifying and then fertilise afterwards to aid grass and root recovery.

Scarifying can take place but an important caveat.

Do not let the blades cut into the roots. Just imagine the blades (tines) going through as though a comb was being pulled through hair.

Aggressive root disturbance now could seriously any real chance or recovery.

[Tony]

Hi,

I'd very much appreciate an impartial view.

I've had an offer of having my grass scarified just now (January). I was surprised, given the conventional wisdom of doing nothing during frosty winter months.

Thoughts/comments welcome.
Many thanks,
Tony

[Philip Voice]

Hi Tony

Thanks for your question. I would be cautious about doing anything to vigorous to your lawn.

Grass will be all but dormant in these freezing conditions and recovery from aggressive treatments will be almost impossible.

I would only ever attempt a light grooming which will remove thatch and debris without touching the soil and disturbing the root-zone.

Hope that helps.

Regards

Phil

[Delrob]

Hi, i have just cut my lawn yesterday and was going to scarify it on friday, do i add feed /weed granules before scarifying or should i do it after scarifying?

[D Marshall]

Hi I have today vigorously scarified my lawn. Please can you advise me now what we can do to the lawn to make it grow - feed and weed or fertilize and what products would you recommend to get a good healthy lawn. Many thanks.

[Philip Voice]

Hi D Marshall

You have to be careful scarifying in stressful conditions and the weather has been rather warm recently meaning the the grass roots will be under a certain amount of stress.

I would feed the lawn but you have to make the decision about watering the lawn and keeping it moist so that the fertiliser can move into the soil and do its job.

Do not add fertiliser unless irrigation is possible. Waiting for rain is the best option.

[Mike Tebbitt]

Hi; I plan to Scarify next week and having never used I am unsure on the affects of my very poor lawn. I also have a problem of a hidden slab of concrete that I know is just below the surface which is to big to dig out. What affect would happen to the scarifier tines if they hit the slab? Also looking at the crop marks I think there is an old path under the surface. I do not want to damage the hired machine.
After scarifying do I seed same day or do I need to prep the area first
Any advice would be grateful.
Novice gardener

[Philip Voice]

Mike

I would be extremely careful of obstacles beneath the surface - why not do a little test dig in the location of the path and concrete slab and perhaps mark out their extremities?

You could bend the tines if you it any hard obstacles and it could be expensive - if the concrete is close to the surface, no amount of maintenance is going to keep the grass in good condition.

You don't need to seed the same day but when you do, make sure that there is somewhere for the seed to dribble into; either the slit/tine marks or aeration holes from a fork or dedicated machine.

It always pays to dress the seed with soil or compost to protect it from birds and dring winds/sun.

[albert.pettit]

when is the best time to scarify the lawn.
albert.

[Andrew]

Scarifying your yard will assist with drainage and the health of your lawn. I run a small Birmingham Landscape Company and can tell you that doing so will save you lots of water and fertilizer!

[Barbara]

Help me if I am wrong but a friend said that after you scarify the lawn you have to put fine sand down first then grass seeds. My lawn has so much moss and weeds in its very hard to find the grass, but I am going to have a go and try my best to have a lawn to be proud of, Wish me luck.

[melvin farrell]

Hi.
I live in the Algarve Portugal. I need to scarify my lawn. As it is January would it be o.k. The weather here is mild 16/17c. Also I have irrigation so water is not a problem. Can you advise me if now is a good time and do you have any further advice.
regards.
Mel.

[Ivar]

I live in Scotland, Edinburgh, and I scarify my lawn once per month from April through to Sept. It's prone to lots of moss.
I apply 4 in 1 fertiliser/moss/weed killer 3 times per year, in April, June and Sept.
I add a little seed after each scarification to help any patches that look a little bare.
Am I doing anything wrong? The lawn seems to be recovering slowly from years of neglect.

[andrew loraine]

hello, I have a large lawn and with the recent hot weather a lot has died or gone lite brown! now that we have had some rain can I scarify and reseed or just leave till end of September? andy.

[Philip Voice]

Hi Andrew

Really best to leave it until the potential for hot weather has subsided.

[Jay]

Hi
I need to scarify about a acre of lawn is this a good time to do it what with the ground being wet and temps are turning
Many thanks
Jay

[anni]

Do you have to kill moss before scarify? Or if scarifyer has a collecthen box can I just scarify withoutmoss kill first? Thanks

[Phil]

Hi Anni

It's best to kill the moss first as it reduces the bulk of arisings when scarifying.