Adding fertiliser to the soil has been practised from the time humans first started gardening, all cultures recognised the need to enrich the soil to aid the production of a healthy crop.  The biggest change to fertilisers came post the Second World War, before that only organic fertilisers were available, usually in the form of animal manure. The fifties saw a greater understanding of the specific needs of plants and new chemical resources.

A healthy well fed plant is better able to fight off pest and diseases but it is important to remember that, no amount of fertiliser will fix a plant that is in the wrong place, growing in poorly prepared soil or is under stress with too much or not enough water.


All plants throughout their growing cycle need nutrients, these needs are provided to the plant from the soil. There are many elements and minerals that plants use, but three that are the most important, as they are used in much greater quantities.

These elements will be represented in all fertilisers that you buy and are referred to as its NPK rating; this rating will be stated on the packet.  Following each letter will be a number; this number represents the percentage of the element in the product. It is important to read these numbers in relation to what they do and what you want it to do.  To give you an example using a high nitrogen fertiliser as a plant is producing it fruit and flower will stimulate green growth when you need to encourage the continued formation of the crop.


There are many other elements that the plant needs but  in much smaller quantities these are called trace elements, often  there will be enough already in the soil. Many fertilisers will include trace elements as a top up for your soil.


Fertiliser is classed as anything that supplies nutrients to a plant and whether they are liquid or dry they are either organic or in-organic, most gardeners will use a mix of both types. 

Organic - Composed of plant or animal by-products in their basic unrefined form. Biodegradable and sustainable organic fertilisers take time to work as they need time to break down in the soil before the plants can use the nutrients. Sheep Pellets, fish manures, blood and bone, seaweed are the most common organic fertilisers that are available

In-organic  - Manufactured or man-made sometimes refined from natural sources but not always. They are then blended to meet the specific needs of a plant or group of plants. They act quicker so more readily available to the plant. Most in-organic fertilisers are sold in dry granulated or pelletised forms, formed to even uniform sized pieces that spread evenly. 

Controlled - This is an in-organic dry prill; this prill has a protective coating, the release of nutrients is controlled by moisture and temperature - the warmer the temperature, the more fertiliser released. Clean and convenient it will feed for the amount of time stated on the packet.  This type of fertiliser is perfect to add when re potting which is why you often see it added to higher priced potting mixes.

Slow release fertilisers – This will do exactly what is says, slowly release its nutrients – this is done simply by the rain or you watering. Check the months that it will feed for then you will know when you need to replace.

Liquid fertilisers - An organic fertiliser, that is readily available to the plant. Usually in a concentrated form ready to mix with water, the nutrients are absorbed through the leaves as well as the roots so you can use a watering can to apply. Perfect for use during the growing season; they won’t burn and can be applied every 10-12 days. 

Soluble fertilisers - A powder form of in-organic fertiliser that needs to mixed and dissolved in water and instantly available for the plant to use. Also applied with a watering can.

A few tips from Team McGregor's

  • Always spread the fertiliser evenly, dumping it in plies will cause fertiliser burn to the foliage.
  • Side dressing is the practise of applying fertiliser to the soil during the growing season; it is spread around the plant or alongside a row of plants. Apply to the soil a 2-5 cm away from the stem and avoid the foliage. Lightly rake or fork it in to the soil and water well.
  • Always water the fertiliser after you have applied it, it needs to get in to the soil to do its work.
  • If applying fertilisers around established trees, shrubs or fruit trees, apply them around the drip line. The drip line is the tip of the branches that extends out from the tree. Follow this line around the tree in a circle as this is where the roots will be as well.
  • Keep a diary it is easy to forget when, what and where you have applied fertiliser.

Guide to McGregor's Fertilisers

McGregor’s PlantMAX 

 N - 14%, P- 3.5%, K-11.6% - Controlled release fertiliser.  It is designed to be applied once at the beginning of the season giving them a good start and feeding for up to 18 months. Use for all shrubs, citrus, rose and containers that have more permanent plantings.

McGregor’s MultiMAX

N-14%, P-3.5%, k-12.5% - This is also a controlled release fertiliser it will release its nutrients from spring through to autumn. Use for containers, shrubs, annual and perennials and soft fruit crops.

McGregor’s VegeMAX

This is a granular fertiliser that will slowly release its nutrients; it also contains added magnesium and trace elements. This is a shorter term fertiliser lasting 10-12 weeks. Use for all vegetables either in the ground or containers.

McGregor’s VegeMAX 

N-8%, P-8%, K-6% - Nice even balance of nutrients for your vegetables.

McGregor’s FruitMAX 

N-5%, P-8%, K - 12% - Higher rating of potash for the formation of fruit and flowers.