Topdressing the lawn
What is top dressing and why top dress the lawn?
Topdressing the lawn is the process of adding a fine layer of ‘home mixed quality soil’ to the lawn surface. Top dressing benefits the lawn as it builds up the quality of the soil over a period of time, - sandy soils will be able to retain moisture better and so the lawn will be more resistant to drought, clay soils will drain better thus improving root development. Another benefit of top dressing the lawn is that it will help to even out any lumps and bumps that are present on an uneven lawn, filling in any small hollows that may develop. Top dressing also stimulates the grass to produce new shoots and so results in denser grass cover which helps combat the onset of weed and moss infestation.
Top dressing is carried out routinely by professional greenkeepers to ensure a top quality finish. If you want a really top quality lawn that can meet professional standards then you should top dress your lawn annually.
What topdressing mixture should I use?
First you need to make your topdressing by combining a mixture of loam, sand and peat. The proportions of these 3 ingredients will vary depending on your type of soil but for a loamy soil type then the following is a good guide: 3 parts sand to 3 parts loam to 1 part peat. The top dressing ingredients should be reasonably dry before you start mixing them to ensure that they are mixed as well as can be expected.
Try and use a good peat rather than garden compost as garden compost can contain weed seeds that will germinate in the lawn. Your sand should be lime free and so sea sand is not suitable.
For heavy clay soils you can increase the amount of sand and reduce the amount of loam.
For sandy soils you can reduce the amount of sand.
The topdressing mixture should be very fine so that it can penetrate the grass surface and reach the existing soil. Because of this you may want to run your mixture through a soil sieve (1/4” holes) before applying the topdressing.
How do I topdress the lawn?
The key to applying the top dressing is to make sure that you get an even spread of the top dressing over the area and to make sure that the top dressing does not remain ‘on top’ of the grass. The top dressing should penetrate down to soil level.
Before you begin you may find that on heavy / compacted soils aerating the lawn a few days before will help your top dressing application.
When your top dressing mixture has been evenly mixed you can start to apply it to the lawn by using a spade to deposit the mixture onto the lawn surface. A general guide is around 1.5-2 kg (3-4 lb) of top dressing mixture per square metre. This figure can be increased for lawns with a more uneven surface.
You then spread the top dressing over the required area using a flat surface such as the back side of a rake or a tool called a lute that is made especially for this purpose. You can make your own lute using a 5 foot long plank of wood. As well as spreading the top dressing over the desired area this action also works the top dressing down into the turfs soil surface. Make sure that the spreading action leaves no bumps on the surface and fills all the hollows in.
Do not leave top dressing lying on the surface of the lawn. If there is excess top dressing left on the grass surface after spreading then remove it
When should I topdress the lawn?
You should topdress the lawn in autumn. Lawns which are based on poor soil will benefit from top dressing the soil each year. Lawns based on good quality soil should not need top dressing every year although if you want a really top class lawn then you may wish to do so.
If you are scarifying the lawn in autumn (September is a good month for this) then you should do this BEFORE you top dress the lawn. Otherwise the thatch (layer of dead grass) will be mixed in with the top dressing and you will lose some top dressing and/or prevent the thatch from being effectively removed.