How to Scarify a Lawn
Scarification or Scarifying is an essential part of cultured turf or lawn management. It is carried out with hand tools such as a Spring Bok Hand Rake or, for larger areas, purpose built machinery called a Scarifier. The aim of scarifying is to produce a healthy vertical type growth of desirable grasses, to improve the turf surface and appearance. Very light scarification (like with a drag brush or rake on a cylinder mower) is used simply to raise the leaves of the grass in the sward before mowing, to leave a smarter looking finish.
It helps to control the knap or grain, which can form on some types of turf. Rather more severe scarification removes dead and dying parts of the turf (thatch), thus letting in air and encouraging new growth. It also brings up stolons of both creeping grasses and weeds, such as White Clover, allowing them to be mown off. Unwanted grasses, such as Yorkshire Fog, have leaves that tend to lie flat below the height of the cut. Scarification, by bringing the foliage up to the mower, results in the grass being less conspicuous. Severe scarification tears out much of the surface growth of weed grasses such as Yorkshire Fog and Couch Grass and can weaken the plant to the point of near elimination. Many seed heads of Poa annua grow very close to the ground and light scarification, or brushing, helps to bring a large proportion of these within reach of the mower with a view to reducing the spread of this less than desirable grass. Many fine turf areas are likely to suffer from an excessive production of fibrous material at the surface, and scarification is a big factor in prevention and cure.
You can hire a ScarifiThese can be hired for a Day, Weekend or Week. Scarification of general lawn areas is concerned with many of the same problems met in fine turf management, but with different degrees of emphasis. If a lawn had not been scarified for a long period of time, or perhaps never before, the amount of material taken out will be enormous and will surprise the hardiest of gardeners. Do not be afraid – this is an operation that can only do the lawn good. Scarification is best carried out in two or three passes in different directions, corner to corner and lengthways. For the first pass, do not set the blades too deep (approximately 5mm is ideal). On the second pass, the blades can be set at no more than 10mm and the final pass can be set a little deeper, making sure not to penetrate the soil.
All material removed from the lawn should not be put on the compost heap, as it may contain fungal spores. Scarification is best carried out in the early autumn, especially if over seeding is to be carried out as well. Light scarification may also take place in the spring, but it must be noted that the grass should be actively growing or severe damage to the sward may occur.
SCARIFYING - STEP BY STEP Check lawn for grass cover. Kill any weeds and moss (using Suphate of Iron) beforehand at least a month beforehand. Mow the lawn really low, almost scalping it to lose the volume of the grass. It will make scarifying so much easier. If the lawn is predominately moss and weeds and weed grasses, after scarification not a lot is going to be left so you will need to over sow. Scarification is best carried out when the lawn is a little moist – not too wet or too dry. Only carry out scarification when the grass is actively growing, so no later than end of October traditionally and never before grass picks up in the spring months.
If there is a serious thatch problem, the spring type tines, which are mounted freely on the axle, should be used. If vertical cutting and seedbed preparation is the target, then the more solid type blades should be used. To set the depth of the blades, go to an inconspicuous area of the lawn and start the blades just flicking the tips of the grass. Set the machine a little lower and go over this small area again. The aim with de-thatching is to go as deep as possible without disturbing the surface of the soil. The aim for vertical cutting is to go deep enough to root prune the grass, so again do not enter the soil. Only when preparing a seedbed should the soil be disturbed but the Scarifier is not a rotovator!!
When the desired depth has been determined, normally by adjusting the front roller, go round the perimeter of the lawn a couple of times as this saves throwing debris into borders and allows a turning circle at the end of a pass. Start by going up and down the lawn in straight lines. Never turn with the blades in the ground. As some machines are supplied with a grass collection box, very little hand raking to clear up should be needed. Workings on lawns that have never been scarified before will necessitate in many empties of the box so it may be easier to leave it off and clear the debris after the second pass. 
If the plan is to blanket over seed the lawn afterwards (and after aeration) you can be cruel to be kind and really give it a good damn scarification! Don't be scared, go for it. After scarification, always mow the lawn again in different directions to the scarification. When scarifying, keep the machine as straight as possible, as it will leave stripes as with mowing. To follow - Aerate and Fertilise and blanket over seed and top dress with a loam. Currently at the time of posting this article, the weather in august is wet so you might be able to start the renovation process a little earlier to take advantage of the available soil moisture but the lawn will look a bit of a mess for around 6 weeks until the new seed germinates.If you want some more information on the Types and causes of Moss, take a look at an earlier post on the subject and Controlling Moss with Sulphate of Iron
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