There’s a difference between renovating your lawn by adding new seeds and by starting from square one with new turf. If more than 40 per cent of the grass in your lawn is damaged, you should go with the latter, but if you’re looking at less than 40 per cent of the lawn being damaged or covered with weeds, a good overseeding – that is adding more seeds to your existing grass plants – will be sufficient. In this article, we will focus on renovating your lawn by overseeding. Helping us is Jan Karlsson, Commercial Lawn & Garden Expert at Husqvarna. If he is to give you just one piece of advice it’s to do a soil test - digging up some soil and sending it to a lab for results. Many homeowners skip this step because they don’t know about it. Or because of the cost. But in fact, kicking the renovation off with a soil test is a solid investment.

“If you don’t analyse the soil, you’ll never know what it needs to get better. You might end up fertilising over and over without achieving any results. A soil test will tell you what to do, but also what not to do. It provides you with a cost-effective action plan”, explains Karlsson.

How to do a soil test varies in different parts of the world, but commercial labs generally do it. The lab will provide you with a detailed mode of procedure that will be helpful when you move on with your renovation.

Renovation season varies depending on where in the world you live, but it’s important to make sure that the ground is warm enough for the seeds to germinate and grow. That means that the ground temperature should be at least 10° Celsius.
“One rule is to wait until after the first cut of the season, when the lawn has turned green and you know that it has started to grow,” Karlsson comments.

If you work out why your lawn has deteriorated, you can use that knowledge to make the right decisions during your renovation. For example, if the lawn has thinned out due to growing trees that shade the lawn and compete for water and nutrients, you should select shade-tolerant grass varieties. You might also want to prune some of the tree limbs, opening up for more sunlight and rainfall.

“You can get some information by just looking at the lawn, but I definitely recommend to do a proper soil test,” says Karlsson.

Start the actual renovation by removing weeds – especially the perennial ones – manually or with a herbicide. This keeps other species from competing with your new grass. If you use herbicides, be sure to read the labels and follow the instructions. Most products will allow you to seed in seven days, but some weedkillers will keep your seeds from germinating for three to six weeks.

Check your thatch status by digging up a small plug of turf, several inches deep. If the spongy layer is more than three quarters of an inch thick when you compress it, it’s time to have your lawn dethatched. If your lawn is larger than 300 square metres, you would want to use a power rake or a scarifier towed by a garden tractor. For smaller lawns, a manual thatching rake will do.

Apart from using it for thatch removal, a vertical mower with a scarifier can be used to prepare the seedbed for new seeds. Go over the entire lawn with the tines set to nick the soil surface to a depth of approximately 1/8 to 1/2 an inch and then rake the large clumps of debris from the site. Another way to prepare the soil is to do an extensive aerifying. If you choose this method, you need to go over the entire lawn 3-5 times to make it completely aerified. However, the very best result is achieved by doing both of the above: aerification followed by vertical mowing. This will strongly improve water supply to seeds and emerging seedlings.

“A soil that’s too dense or the ground is too hard are common problems for landowners. It makes it hard for water and oxygen to reach the roots of the grass plants, which leads to poor growth. An aerator creates ways into the soil for the air and water and a vertical mower with a scarifier splits the grass plants, leaving you with more plants and a thicker lawn.”

Grass seeds and seedlings need water to germinate and root. Your ground doesn’t have to be soggy, but make sure the soil is at least moist. If the lawn feels dry and the chances of rain are low, start building a reserve of water in the soil by running the sprinkler for an hour or two a day several days prior to seeding.

“To keep your lawn evenly supported with water is very important. If you do that and the ground temperature is decent, you are well on your way”, Karlsson points out.

Fertilisation will encourage establishment and growth of your new seeds and seedlings and should be done just prior to seeding. Apply a slow-release nitrogen fertiliser. If you’ve done a soil test you’ll know if your lawn also needs additional phosphorous and potassium.

When your lawn is in relatively good condition, you can use the seed mix you used in the past. If you’ve done a soil test, you will have a good indication of which seeds to use.

You can spread the seeds by hand, but if you want to make sure that the seeds are spread evenly, the best thing to do is to use a spreader.

“Some spreaders can be connected to your scarifier. I would recommend a centrifugal spreader,” adds Karlsson.

“There is no need to wait a certain amount of time before you start enjoying your newly renovated lawn. When you’ve overseeded it, you can start using it right away, mowing it as you normally would,” says Karlsson.