The Fertiliser Guide

The Fertiliser Guide
The Fertiliser Guide

A wise man once said, ‘good lawn management calls for a regular lawn feeding programme’. We couldn’t agree more with Dr D.G.Hessayon, who said this exact sentence in the gardener’s unofficial bible – The Lawn Expert.

Garden lawns benefit massively from lawn fertiliser feeding. Grass is a fast-growing plant; without these extra nutrients, it will soon use up food reserves in the soil. When this happens, the grass will go pale, and your lawn will begin to thin out or stop growing in the worst-case scenario. The best way to keep your lawn growing strongly is by using fertilisers. And our fertiliser guide will help you get the best results when using them.

If you agree with Dr D.G.Hessayon's wisdom or want to enhance the growth of your garden lawn, then our Fertiliser Guide is the right place for you. 

In this lawn fertiliser guide, we aim to cover the science behind fertiliser, what it's made of and when in the year is the best time to use it.

You can read our 'Fertiliser: What is it? guide to help you understand what fertiliser is and to give you more understanding of what this guide talks about. This post offers advice that will help get you up to speed on building your knowledge of garden fertilisers. It also helps to know how to easily keep your pets and local wildlife safe when using fertiliser.

Our step-by-step fertiliser guide

Are there times of the year when I should and shouldn't use fertilisers?

The truth is you should apply a fertiliser feeding schedule. It is ideal to follow a schedule for most of the year while avoiding January and February when your lawn is dormant.

One of the best times to use fertiliser is in autumn.

The rest of the year is fine for fertiliser use, but we will discuss that in more detail later. We will also look at how to sow fertiliser, giving you insight into best practices, techniques and safety.


It is commonly thought that the main purpose of fertiliser is to make grass green. While it is true that this happens, a typical compound fertiliser will do more than just that. 

What are the benefits of Compound Fertilisers?

By using a compound fertiliser instead of just the lawn nutrient on its own, you’ll see that the grass really is greener on the other side. Not only will the grass be green, but the compound fertiliser helps the grass to be well established and better protected against disease come autumn/winter. 

So, what is a compound fertiliser? Find out in our ‘Science-y Bit’ below.

Guide to the elements in lan fertiliser

Next up, we’ve got the science-y bit of fertiliser. This section details what your lawn needs and what is in fertiliser. 

The three nutrients that any lawn needs are: NitrogenPhosphate and Potassium – also known as the acronym NPK (each letter represents the nutrients element initial).

These nutrients all serve varying purposes and, when combined to make a compound fertiliser – are very useful.

  • Nitrogen (N) is responsible for giving the lawn its lush green colour by stimulating leaf growth and helping to establish the lawn.
  • Phosphate (P) is known for building up the root system and improving seed-to-soil contact.
  • Potassium (K) can help to harden grass so that it builds up immunity/tolerance to disease and drought.

The goal of our spring/summer fertilisers is to make grass grow green and establish the lawn quickly - and this is evident in their NPK breakdown. 

Quick Release and Slow Release Fertilisers

An example of the NPK level of our QUICK RELEASE: Spring / Summer is 9.7.7. 

This shows that the Nitrogen concentration is slightly higher than the Phosphate and Potassium. This encourages fast growth and greener grass with the added bonus of a strengthened root system and protection against drought. As there isn’t much difference between the levels of each nutrient – you could consider this fertiliser as a bit of an ‘all-rounder’ to kick start the spring season. 

An example of a slightly different NPK level to this would be our SLOW RELEASE: Spring / Summer fertiliser which has an NPK of 12.6.6. 

You can tell that the concentration of Nitrogen is double that of the Phosphate and Potassium concentrate. This means that it will help your grass grow greener and stimulate leaf growth over a longer period of time in comparison to our Quick Release. But it will also slowly build up your lawns root system and tolerance against drought, disease and discolouration.

When to Fertilise a Lawn 

There are some other fertiliser factors to consider besides NPK levels. Weather, season, types of fertiliser (granular/liquid) and how to apply them will influence your final fertiliser choice. You will also need to consider what the main utilities and characteristics of the lawn are and what you are expecting from the lawn.

The Ideal Weather to Fertilise

Whatever season, or for whatever reason you may be fertilising your lawn – you should do it a few days after the weather forecast is to be ‘showery’. However, try not to do it when it is actually raining! 

The ideal day to fertilise your grass is when your grass is dry, but the soil is still moist. This allows it to absorb the fertiliser you are applying. If you can, please avoid applying fertiliser when there has been a prolonged dry weather period. If you really must apply lawn feed, hose down the lawn and apply the fertiliser the next day when the grass has dried. 

Once you’ve applied your chosen fertiliser, you should hope for some showery weather to roll back again so the soil can absorb the feed further. If the rain has gone to Spain and doesn’t make an appearance – hose down the lawn again to give it a little help along the way. Remember you can manually water your lawn if needed, and if you can, try and do it on an overcast day.

The Best Season for Fertilising your Lawn 

You’ll find that most fertiliser products will specify the season they are for. At The Grass People, we specify our fertilisers by Autumn/Winter, Spring/Summer. 

Different fertiliser mixes with different NPK concentrate levels are created specifically for each season. As we previously covered, varying Nitrogen, Phosphate and Potassium levels can have different effects on your grass. Although a high concentration of Nitrogen is useful in a Spring/Summer fertiliser, it won’t be in an Autumn/Winter fertiliser when you’re hoping to give the mower a much-needed break!

Types of Fertilisers

There are two types of fertilisers – liquid and granular. For our domestic fertilisers, we promote a granular product. Granular fertiliser is a foolproof fertiliser and may cause less scorching as the fertiliser goes directly into the soil. Alternatively, a liquid fertiliser may end up coating the blades of grass if not used correctly. In short, a liquid fertiliser takes much more preparation and expertise. In addition to this, the liquid fertilisers we sell could fertilise a football pitch!

Fertiliser guide tips for application types

There are four main ways to apply fertiliser to a lawn, and this is where the type of fertiliser does matter. Be aware that no one should apply liquid fertiliser with their bare hands!

The four main ways are:

  • Hand Application – used for granular fertiliser to scatter across the lawn.
  • Hand-Held Distributor – there are two types on the market – one that requires you to wind the handle to distribute granular fertiliser and another that has a nozzle to allow you to spread the liquid fertiliser.
  • Liquid Dilutor – this is for liquid fertiliser that is spread through a hose.
  • Wheeled Distributor – this one requires quite a bit of skill and is for granular fertiliser – completed correctly, you should be able to thoroughly cover the lawn.

There are pros and cons to each method. Ultimately you should choose the application method that is easiest for you, suits the fertiliser product you intend to use and will provide full coverage without the risk of scorching and/or double-dosing your lawn.

What to expect from fertilising a lawn

Fertilisers can be quick or slow acting depending on their NPK levels which will also dictate what time of year they should be used. A quick way to understand what to expect from fertilising a lawn is to check the NPK level on the fertiliser you have chosen – this will give you the best indication of the speed at which your lawn should go green / establish and be protected against disease.