Using a Lawn Raker or Scarifier
Ready the Lawn for Scarifying or Raking
Planning ahead is important. You need short dry grass for raking or scarifying so bring the grass height down gradually over a week or two before hand. This doesn't shock the grass whilst also allowing air deeper into the turf helping dry the grass.
If you have any weeds in your lawn then you had best get them a week before you scarify. Though scarifying can help control some creeping weeds, nothing is more permanent than a little correctly timed and placed weed killer.
The final bit of preparation is to have good soil moisture so that the lawn recovers as quickly as possible afterwards. If there is too much (soft ground) or too little (dry hard soil) you need to either wait until the conditions improve, assist them to improve or not rake or scarify at all.
The day before attacking the lawn mow it as close as possible without scalping. Long grass just creates resistance to the scarifier with ultimately more rubbish to collect. Dry grass and moss makes life a lot easier as well. Plan to rake on a dry day with no dew around. The afternoons are often best. If the weather doesn’t play ball, keep the grass short until you get another raking opportunity.
Manual Scarifying or Raking
If you're using a hand held rake wear leather gloves with talc in them to prevent blistering. Good pressure is required and rake vigorously and repeatedly to lift out the moss or thatch. The easier option, and therefore the better option in my mind is to invest in a proper lawn scarifier* that has wheels such as the one itemised above and shown opposite. It's far less work and just as effective.
You will find it easier and get better results by doing the lawn once in one direction and repeating the raking in the other. Use the mower or a landscapers rake to collect the debris.
Using Powered Scarifiers or Lawn Rakers
If you’re using an electric raker then repeated runs up and down the lawn to ‘tease’ the moss or thatch out will be best for the machine and grass.
If you’re using a petrol scarifier you have the power to go deep but don’t! Teasing the moss or thatch out with progressively deeper runs is the best way.
If your machine has height adjustment (most do) then set it up (turned off please) on a hard surface so that the blades or wires just touch the ground. Then do a few metres on the lawn and make minor adjustments so that debris is removed without great chunks coming up – tease it out!
Moss and thatch collection is often best with a large 2 to 3 foot wide ‘landscaper’s or hay rake’ or by using the lawn mower. The mower does an extra cut helping the debris to pack better. The box is also normally bigger than those on rakers or scarifiers so I suggest leaving the box off the scarifier.
If the moss or thatch is particularly bad you may need to collect it regularly to keep the lawn clear for the next run with your scarifier.
Changing direction for the second and progressive runs is beneficial. You’ll remove more each time and complete the job sooner.
As progress is made and less debris remains you can lower the machine for each new run. If you are scarifying with blades you can even allow the machine to penetrate the soil by up to ¼”. This also helps seed to take if you are going to wisely over seed the lawn on completion. If you are using an electric lawn raker or wire tines in your scarifier or mower then keep them off the soil as they cause too much damage and can also break.
At some point you have to decide how far to go with debris removal. If the moss or thatch is not particularly bad or you’re doing this in spring then two runs, one up and down and one across should suffice. Keeping the machine on the high side will minimise damage and enable the lawn to recover in no time with a little rain and fertiliser. However, if the problem is bad and the conditions are good, then a total of four or five progressively deeper runs is in order. The resulting landscape (not too dissimilar from the dark side of the moon) may well scare you, in fact, it should scare you but, with a little help it will come back better than ever!
Scarifying and Raking Tips
If your lawn is on anything more than a gentle slope you may have to resist a heavy scarify as any seed added to aid recovery may easily wash away if there is heavy rain. Consider moderate scarifying so that enough grass remains to hold the seed in place should a deluge occur.
If there are bumps in the lawn you may cause damage in these areas even though you are only raking or scarifying lightly. Unless you take action to correct the bumps this damage will be inevitable and perhaps typical of most lawns. Don’t worry, just follow the recovery procedures and in a few weeks the lawn will be as good as new.
If shallow dips or bumps are a problem and you feel that top dressing will resolve much of it then top dressing (3-4 kilo per square metre) after scarifying is ideal. If you’re also overseeding this is even better. Depending upon which book you read some say seed then top dress and others top dress then seed. I’m in the latter school. See Soil & Lawn Top Dressing for more detail.
Sometimes thatch is so bad that, as explained earlier the lawn has rooted into it. In this case either great lumps of lawn will literally pull away or you end up with just thatch and no grass. In this case you need to consider whether neglect is the cause or if soil compaction and disease is the cause. If it is the latter consider a new lawn, if it is the former just keep going with the scarifier until you get down to the soil. The likelihood will be that, in a heavy thatch situation, you will remove most living grass; therefore you will have to re-seed the lawn. The moral of the story; A stitch in time....! See Over Sowing with New Grass
If you’re feeling really adventurous this is also a good time to hollow tine or spike the lawn. Just follow the instructions in Lawn Aeration & Equipment
NB If you are de-mossing you don’t need to kill the moss first. For more info go to Moss Control