Scarifying a lawn is not something you do to get into the spirit of Halloween. Nor is it a spell from the Harry Potter universe. Scarifying a lawn means to break up, loosen, or roughen its surface. Why would you want to do that? Well, over time lawns tend to acquire thatch. Thatch is what happens when organic debris such as dead grass, moss, leaves, stems, and weeds build up. This build up can prevent nutrients, oxygen, and water from getting through the soil to the roots of the grass. In such a situation, a large chunk of the moisture that should be slaking the thirst of the grass ends up just sitting on the surface instead, creating ideal conditions for the growth of moss. To add insult to injury, thatch has very little nitrogen, but a whole lot of carbon, which is certainly not the way to have grass that is green. If allowed to remain untreated, thatch can create a breeding ground for plant disease and insects. The worst cases of thatch can kill a lawn completely.
Scarifying a lawn is the process of cutting through the topsoil to break up the moss or thatch. What this does is aerate and loosen the soil, which makes it healthier and more able to grow seed. As an added bonus, scarifying also gets rid of any weeds that might be lurking.
What to do before scarifying
Before you scarify a lawn, you’ll need to mow it a few times first, beginning a week or two beforehand. The day before you scarify, mow the lawn one more time, at the lowest possible setting. The whole scarifying process is easier and more efficient when everything is as short as you can get it – but do take care not to scalp your lawn. Remove any weeds by hand, but do not use weed killer, which not only messes up the natural weed killing process, but runs the risk of killing any new grass seedlings. Make sure the ground is reasonably moist, but not soggy. This will help the lawn bounce back as quickly as possible.
How to Scarify a Lawn
There are several ways to scarify a lawn, and which method you choose will depend on your individual circumstances. For those whose lawn is really just a patch of grass, a garden rake might be sufficient. However, you’ll want to wear a sturdy pair of gloves sprinkled on the inside with a baking soda or cornstarch based powder in order to keep your hands from getting blisters. If you have a larger span of grass – or don’t fancy using a rake – your best bet is a manual or electric lawn scarifier. Manual lawn scarifiers look a great deal like manual lawn mowers, only instead of wheels and horizontal blades they have wheels and vertical blades or tines (blades are more effective against thatch). They also resemble manual lawn mowers in the way they are operated; simply push the scarifier down the length of the edge, take a step in, then turn around and push in the other direction, repeating until the entire lawn has been scarified.
Related: Lawn Scarifier Reviews
For those with even larger lawns, there are electric scarifiers and scarifiers that run on petrol. These are used in a similar manner to their electric and petrol mower counterparts. Like the manual mowers and scarifiers, the first pass should be down and up in strips.
No matter which scarifier you use, it’s vital not to let it cut too deeply. Most scarifiers have adjustable blades or tines; to make they are set at the right height, place the scarifier on a hard surface, and make certain that the blades or tines are just touching it. You want to scarify, not plough. The idea is to coax the stuff out of the grass, not yank it and great globs of soil out. You’ll know after a few feet if you’ve adjusted the height correctly.
After the first pass of scarifying, you’ll need to collect the debris. For smaller spaces, a hay or landscapers rake is just the thing. For larger spaces a petrol or electric lawnmower is best.
Once you’ve made the first pass and cleaned up the debris, you’ll want to scarify at least one more time. For this second pass, take a diagonal approach - meaning your second set of scarified strips should be at a 45-degree angle from the first set. This applies to manual, electric, and petrol scarifiers. You should also consider lowering the height of the blades or tines a little. As with the first pass, collect the debris so that you have a clean slate.
How many subsequent passes you make will be determined by the state of your lawn. If your lawn doesn’t have a big moss or thatch problem, or you’re doing the scarifying in the spring, two passes might very well be all you need. On the other hand, if you do have a big moss or thatch problem, you’ll probably need to make four or five passes (in the Autumn).
After you scarify
Once you’ve finished scarifying your lawn it is a wise idea to over seed it with fast growing grass seed, so that weeds don’t end up replacing the grass you’ve taken such pains to save. Of course, if your moss or thatch problem was really bad, then you might have to try lawn moss killer products or failing that, completely reseed the lawn.
When to scarify your lawn
If all your lawn needs is a little scarifying, then you can do it either in the spring – usually in April – when it warms up, or in the Autumn – usually in late August or September, when the rain has begun but it hasn’t yet gotten cold. That way, your lawn will have time to recover.
If your lawn needs major scarifying, then you’ll need to do it in the Autumn in most cases. This is because major scarifying by its very nature leaves the lawn thin in most places and bare in the rest. This creates the perfect canvas not only for new grass seed to grow, but also for any stray weed seeds that might be lurking about. By saving major scarifying for Autumn, you’ll avoid most of those weed seeds.
However, there are cases when major scarifying should be done in the spring. These cases are as follows:
- You were unable to do it the previous Autumn, and it really, really needs it. You might end up with more weeds than you’d like but waiting until next Autumn could mean dealing with a lawn that’s dead as a door nail.
- The space you need to scarify is shady. Coverage in shady areas tends to thin out over the winter anyway, so scarifying in the Autumn will just exacerbate the problem.
- The space you need to scarify is under trees. While the leaves are still on the trees, they will create shade, but when those leaves fall they diminish the health and vitality of the grass underneath. In the earlier part of spring, the trees are still bare, which will allow the sun to shine through and encourage the new grass seed to grow.
I am the editor of Lawn Mower Hut and produce most of the content on the site. I have over 25 years experience in the gardening industry and have worked in multiple roles throughout that time. My passions are gardening and golfing. If you have any questions please get in touch I will be happy to help.