When it comes to feeding a lawn, many gardeners get it wrong, either by applying too much or not enough.
So, how much lawn feed should you apply?
It can be difficult to provide an answer because there are many variables including;
- The product used
- Whether it’s a liquid or granular feed
- What the NPK values are
- The time of year
- The weather
To point you in the right direction, I’m going to offer you my advice.
The Manufacturers Guidelines
All domestic lawn fertiliser products come with a recommended application rate so check the product label.
If a label advises you to spread 25 grams of lawn feed per square meter, you would require 2.5kg of lawn feed for a 100 m2 lawn.
It’s a decent guideline but they often require tweaking.
You Shouldn’t Always Follow the Advice on the Label
Because these are often the maximum application rates for a given product.
Most labels provide a warning along the lines of, ‘DO NOT exceed the maximum recommended rate of 25g per sq. metre.’
Applying even the maximum dose is rarely a good idea.
There’s Too Much Nitrogen in Most Domestic Fertilisers
Domestic lawn fertilisers are designed to make you think the product has worked, as quickly as possible.
You apply them and watch the lawn become greener and grow faster. The product has clearly worked so you buy the same grass feed again when your lawn needs feeding.
The ingredient which causes this dramatic growth and lush green colour is nitrogen.
So, fertiliser manufacturers simply add lots of nitrogen to their fertilisers to provide the best results.
Unfortunately, this excessive growth and greening usually occurs at the expense of healthy root development as the roots grow too quickly.
This fast root growth causes another problem which is excessive lawn thatch.
New roots grow much quicker than microbes in the soil can break down dead grass roots and organic matter. The result is a build-up of thatch that happens quicker than it normally would.
The Type of Grasses Your Lawn is Made Of
Different species of grass require different amounts of fertiliser.
An ornamental lawn that consists of fine fescue grasses naturally produces a lot of thatch so applying too much fertiliser will exacerbate the problem. Too much lawn feed or fertiliser also turns this type of grass a blue colour.
For ornamental lawns, a dose of 20g of lawn feed per square meter is sufficient.
Lawns made up of ryegrass take well to a higher dose, so 25g to 30g of lawn feed per square meter is a good amount.
You could also apply some liquid feed a few weeks later but make this a half dose due to the high nitrogen content. We’ve outlined the differences between granular and liquid fertilisers in a separate article.
The weather also determines when you should feed your lawn as well as the amount of fertiliser you apply.
If there has been lots of rain which means good grass growing conditions, apply it at the upper end of the application range.
This equates to 25g per m2 for an ornamental lawn and 30g per m2 for a normal lawn.
If ground moisture is present but it hasn’t rained, use the lower end of the scale.
20g per m2 for an ornamental lawn and 25g per m2 for a normal lawn.
If it has been hot and dry for weeks, don’t apply any fertiliser as it could cause scorched, brown grass.
Learn how to apply granular lawn feed with our guide.
Why You Should Be Careful with Weed and Feed Products
Weed and feed products need to be applied carefully as too much nitrogen can damage grass as can too much weed killer. If your chosen product contains moss killer too, your grass can really suffer.
This means you should be applying less than the recommended dose as with regular lawn feed, although this may not kill every weed.
This approach takes more time but gives you ultimate control over how much of each product is applied.
Domestic fertilisers are adequate for most gardeners. They’re also the only product available to amateur gardeners. Professional products are very expensive in comparison and require specialist knowledge for their safe use.
When used properly, domestic lawn feeds are good products. It’s important to get the application process right for granular fertilisers and liquid feeds to make sure you don’t apply too much.
Grass is a hardy plant and needs less fertiliser than you might think to stay strong and healthy, so underfeeding is always better than overfeeding.