Overseeding: How to Plant a New Lawn over an Old Lawn

Lawns are bound to take lots of beating from weather elements like snow. This may leave some areas with more grass and other patches with no grass at all. At times, weeds and mosses may take over your lawn, leaving it looking messy and very unpleasant. 

In this case, you start thinking of a new lawn. Since planting a new lawn from scratch takes lots of resources and time, overseeding remains the best option. It involves a few steps that include: dethatching, raking, aeration, sowing, and maintenance. 

So now we ask ourselves, how do you plant a new loan over an old one?

How to Overseed your Lawn

Here are the steps for planting a new lawn over an old lawn:

Step 1: Dethatching

When weeds and moss take over your lawn, it is left with some patches that have less amount of grass than the rest of the lawn, while some do not have any grass at all. At times, the grass in these patches may have turned brown or discolored. 

So, before you begin your overseeding work, you must first get rid of the unwanted grass and debris in the patches. This process is important because the overlying thatch and organic material that comprises dead green matter can prevent the new grass from thriving. 

You should, therefore, get rid of such matter to allow sunlight, nutrients, and water to penetrate the soil. You can get rid of the thatch by using a mechanical dethatcher. You can easily get from a local agricultural outlet.

Step2: Mowing

Before overseeding, you need to get rid of the browned or unhealthy grass patches. Also, the size of the grass needs to be reduced to a level of not more than 1 ½ inch. This allows sunlight and nutrients to reach the roots of the new grass. 

But even as you do your mowing, remember to remove the clippings to create room for better seeding when the time comes. You can use your handheld mechanical mower to do the job. When mowing, ensure to overlap your paths slightly to achieve a uniform grass height all over the lawn.

Step3: Aeration

The next step in land preparation when overseeding is aeration. Aeration of the lawn is important because, by this time, your lawn soil is very compact, such that the roots of the new grass may not go deep enough into the ground for enhanced growth. 

We advise using the hollow tine aerator over the solid tine one. This is because the solid tine aerator only pushes the soil further down, hence compacting it even more. On the other hand, the hollow tine aerator breaks the core of the soil, allowing the roots of the new grass to penetrate deep. 

Step4: Sowing

Then comes the main event of the process: the sowing of the new grass seed. But before this, you should have your soil tested. Soil testing is important because it helps decide what type of grass does well in your soil, since different soil PH supports different species of grass. 

You can take some small samples of your lawn soil to the agricultural department near you for testing. When it comes to sowing the new grass seed, I advise you to use a seed spreader so that you can achieve a uniform distribution of the seed. Ensure to overlap each pass to eliminate bare spots in the lawn. 

Step 5: Maintenance

Sowing the seed is not enough; it must be followed by effective maintenance of the seed until it grows to the level of the old grass. After you have sown the new grass seed, you can apply a thin layer of topsoil.

This helps in hiding the new seed from the birds’ eyes and the elements. It also gives the seed a solid medium for proper and faster germination. Besides, the seed will be deeply rooted in the soil and will not be displaced when watering the lawn. 

Alternatively, you can mulch the new grass seed with straw. This also helps in reducing the loss of water through evaporation. By doing this, you can be assured of almost 99% germination of the new grass seed. When the grass is grown, do not mow it until it is ¾ inch taller. 

Do I need to remove old grass before overseeding?

Whether or not you need to remove old grass before reseeding depends on the condition of the existing grass in the patchy areas. If it is browned or heavily infested with weeds and moss, then you can consider killing it altogether. 

If it does not have so much weed or is still in good condition, then you can opt to kill only the ones you want to do away with. To kill all the grass in the patchy areas, you can spray it with a chemical kill. And as you do that, ensure to bring the nozzle of the sprayer close to the grass to avoid killing even the one you would want to retain. 

The only disadvantage with this method of grass killing is that once it gets into the soil, it may affect the normal, proper growth of the existing and the new grass because of the surge in PH levels. 

The alternative is to cover the old, unwanted grass with a black poly film. This prevents sunlight from reaching the grass, hence killing it, but this is if you want to remove the old grass altogether. The best method of removing old grass from the patchy areas is by using a sod cutter. 

How long after killing the grass can I overseed?

Whichever method for killing the old grass you decide to go with, the grass takes between 2 and 3 weeks to die, after which you can sow the new seed. Dead grass is usually dry and brown, resembling hay. 

And because it dies together with moss and weeds, you will need a rigid tine rake to remove it. Do not throw the dead grass away yet; you might need it for mulching after sowing the new grass seed. You could also use the grass for compost and use the fertilizer to grow veggies in your kitchen garden.

Final thought

Spreading grass seed directly over an existing lawn without tearing up the soil or replacing the turf is an easy way of enhancing lawn density, improving color, and resistance to drought and diseases. It is faster than starting a new lawn from scratch and saves on many costs.