Understanding fertilisers

Maintaining a glorious garden brimming with scented flowers and vibrant foliage is easy - just give plants what they want:

  • Water
  • Sunlight/Shade
  • Nourishment

You’ve already chosen their positions and you know how to wield a hose, but how do you make sure they have all the nutrients they need to develop strong roots, masses of flowers and lush foliage?

By using fertilisers, of course!

Let’s take a look at what you need to know to select the right fertiliser for your garden, including:

  • Types of fertilisers
  • Understanding fertiliser ratios
  • What to use and when
  • The importance of pH
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light-bulb-icon@2x.png What you need to know

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The type of fertiliser you choose will have a huge impact on the health of your garden. There are lots of options available, and choosing the right one at the outset can save you time and money in the long term.

Types of fertiliser

The most common types available:

  • Organic based - either certified 100% organic or including organic matter
  • Composts and soil improvers
  • 'Instant hit' powder, granular and liquid fertilisers
  • Slow-release fertilisers
  • Controlled release fertilisers

Learn more about the frequency, pros and cons of each 

Understanding fertiliser ratios

Fertilisers are combinations of essential elements (nutrients) that have been mixed at specific ratios to encourage plants to grow, flower or fruit.

 

  • Fertiliser manufacturers list these ratios on the packets, usually shown as N:P:K or Nitrogen (N), Phosphorus (P) and Potassium (K). These are the macro or major chemical elements that directly impact plant growth and development.

  • Plants also require micro nutrients and trace elements to maintain optimal health. To see what these are and why they are important to plants, look at Fertiliser Components and their Uses

Most fertiliser packaging will include a Guaranteed Analysis that lists all major, minor and trace elements included and their relevant percentages or parts per million.

The importance of pH

  • The pH of your soil determines the availability of some nutrients
  • Test your pH every 3-4 years and adjust accordingly
  • pH should be between 5.5 and 6.5 for most flowering trees and shrubs.

To find out more about soil pH and healthy soils read our story
How to establish a new garden bed

light-bulb-icon@2x.png What fertiliser and when

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Different fertilisers are required at different stages of plants' lifecycles. Whether it's establishing a new tree or encouraging more flowers and fruit, there's a fertiliser to suit each stage of growth and development

Plant type

Young and newly planted trees

What: Use a high nitrogen fertiliser to help develop strong growth.

 

Note: Additional applications of chicken manure will also be of benefit.

Acid-lovers like gardenias, camellias, azaleas and roses.

What: Use a fertiliser like Osmocote Plus Trace Elements for Roses, Gardenias, Azaleas & Camelllias which has been specifically designed to give acid-loving plants the nutrients they need to flourish

 

Note: Use a controlled release fertiliser to ensure the right nutrients are available when required.

Native trees and shrubs

What: Use a fertiliser designed for phosphorus sensitive plants

 

Note: Native plants need fertiliser but they are accustomed to phosphorus-deficient soils and will react badly if high P fertilisers are used.

Flowering plants

What: To encourage flowering, most plants benefit from a fertiliser high in phosphorus like Miracle-Gro MaxFeed Flowers & Blooms which has NPK 16 : 7 : 18 This is best applied as needed in Spring and Summer

 

Note: Use an all-purpose controlled release fertiliser  twice a year, and apply liquid feeds throughout spring and summer for maximum wow!

Dormant (deciduous) trees and shrubs

What: Do not fertilise them while they are devoid of leaves!

 

Note: Wait until the first signs of new leaves and flowers appear in Spring before fertilising

Additional fertilising

What: Pure Organic Premium Seaweed Planth Food will improve plant health as well as pest and disease resistance.

 

Note: Liquid fertilisers help to give plants an instant boost as they contain a mix of macro, micro and trace elements.

Tips, tricks & advice

How to establish a new garden bed

Step by step guide to establishing new garden beds including:

Read more

Drought proofing your garden

Growing a beautiful garden in drought conditions is easy with:

Read more

Other products you might need

Osmocote® Plus Trace Elements: Total All Purpose

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The smart way to fertilise the entire garden - one easy application feeds continuously for up to 12 months

Osmocote® Plus Bio Stimulants Roses, Gardenias, Azaleas & Camellias

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Easy to use, double action liquid plant food for roses, gardenias, rhododendrons and similar shrubs that prefer an acid ('sour') fertiliser and soil to perform well

Osmocote® Plus Trace Elements: Roses, Gardenias, Azaleas & Camellias

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A set & forget plant food for roses, gardenias, rhododendrons and other shrubs that prefer an acid ('sour') fertiliser and soil to perform well

Osmocote® Plus Trace Elements: Native Gardens

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A low phosphorus complete plant food developed specifically for Australian native plants and members of the protea family

Miracle-Gro® MaxFeed Flowers & Blooms Plant Food

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Water soluble fertiliser that gives flowering plants (apart from natives) the nutrients needed to produce larger, better coloured and more abundant blooms

Osmocote® Plus Bio Stimulants All Purpose

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Easy to use, double action, all purpose liquid fertiliser feeds for up to 3 months with the added benefit of bio stimulants to boost soil and plant health.