Fertilising Citrus Trees in Australia (+ Best Citrus Fertiliser)

Citrus trees need all of the three major nutrients of nitrogen, phosphorus, and potassium.

In Australia, we love growing all types of citrus trees in our gardens.

However, for the trees to produce their fruit, they do need regular fertilising so that their roots can take up the nutrients needed for healthy growth and strong fruit production.

The best fertiliser for citrus trees in Australia

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Citrus trees need all of the three major nutrients of nitrogen, phosphorus, and potassium.

The nitrogen will promote plenty of leaf growth, the phosphorus will help with developing a strong root system, and the potassium will assist the tree to produce plenty of fruit.

In addition, citrus trees also benefit from some extra iron as this stops the leaves from going yellow and dropping off the tree. Remember that leaves are important for the tree to photosynthesize and continue to grow.

Whenever possible, I prefer to use natural fertilisers on my citrus trees. They are better for the soil, the plants, and the environment.

The best types of fertilisers for citrus trees are:

It’s also a good idea to alternate between using different fertilisers at different times of the year. This ensures that your trees are getting all the nutrients that they need and keeps the soil healthy.

How to fertilise citrus trees

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Applying fertiliser to your citrus trees is fairly easy. Here’s what to do:

  • Water the soil around your tree first
  • Scrape back any mulch to expose the soil
  • Spread the fertiliser around the base of the tree under the canopy but keep it away from the trunk
  • Water again and replace the mulch

There’s no need to dig the fertiliser into the soil and this should be avoided because you might damage the roots. The water will move the nutrients down into the soil.

When to fertilise citrus trees

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Ideally, you want to fertilise your citrus trees four times a year to ensure that they get an adequate amount of nutrients. This should be done once in spring, summer, autumn, and winter. 

The exact timing is not critical but, according to Jerry Coleby-Williams from Gardening Australia, you should not fertilise when the trees are flowering as this will produce plenty of new green growth but not many fruits.

It’s also recommended that you apply some extra trace elements such as iron, calcium, sulphur, and magnesium to your citrus trees in spring and summer.

Yates Trace Element Health Tonic (view at Amazon) is a good option because it contains a complete range of essential trace elements and releases nutrients gradually to minimise leaf burn.

You can also purchase trace elements from your local garden centre.

However, you need to be careful not to apply these in large quantities because they can harm the trees. Be sure to follow the instructions on the pack carefully.

To keep your trees really healthy and thriving, you can also supplement these fertiliser applications with a dose of liquid seaweed such as Seasol.

This will help to condition the soil and make it easier for the roots to take up the nutrients including the trace elements.

Being a liquid feed, you can apply this once a fortnight without any danger of overfeeding. This is because liquid seaweed does not contain any of the essential nutrients but just helps to promote the health of your trees.

Homemade fertiliser for citrus trees

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The best homemade fertiliser that you can use on your citrus trees is matured compost. Making your own compost is easy if you use a compost bin or tumbler and it should form part of your sustainable gardening routine.

You could even go one step further and start a worm farm. Worms are the ultimate experts in breaking down organic matter and producing excellent waste material referred to as castings. These castings are high in nutrients and your citrus trees will love them.

Most commercially available worm farms will have an outlet tap where the liquid produced can be dispensed from. This liquid worm waste is referred to as worm tea.

All you have to do is take some of this worm tea, mix it with water and apply it around the base of your trees.

Another thing to remember is that if your citrus trees are not producing fruit, it probably means that they’re not getting enough potassium.

Encouraging older citrus trees to fruit

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When I moved into my current house, I noticed a fairly mature lemon tree that had been sorely neglected, probably for many years. It was not growing in the ideal spot and was not producing any lemons.

So, I decided I would try a few things to see if I could encourage it to fruit. The first thing I did was give it a good prune to remove a lot of excess growth and overlapping branches. Then, I gave it a dose of Dynamic Lifter.

Because I have a fire in the house, I get a fair bit of wood ash that I always put out onto various areas of the garden. As you might be aware, wood ash contains ample amounts of potassium.

During the first winter in this house, I would often scatter the wood ash around the base of the lemon tree. Now, for the first two years, the tree did nothing except put on plenty of new growth.

I gave it another more gentle prune and finally this year, the tree is producing some lovely lemons and plenty more flower buds are forming.

I do believe that adding the wood ash to the soil was one of the reasons that the tree is now finally fruiting after two years.

Citrus Fertiliser FAQ

Is cow manure good for citrus trees?

Cow manure is excellent for citrus trees as it contains all the essential nutrients that the trees need.

Is blood and bone good for citrus trees?

Yes, blood and bone is great for citrus trees because it contains essential nutrients. It also usually includes cow manure and helps to improve soil health, structure, and drainage.

Is Seasol good for citrus trees?

Seasol is good for most of the plants in your garden because it’s a soil conditioner and will help to improve the health of your plants. Standard Seasol is not a fertiliser as it does not contain essential nutrients such as nitrogen, phosphorus, and potassium.

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Annette Hird

Annette Hird is a gardening expert with many years of experience in a range of gardening related positions. She has an Associate Diploma of Applied Science in Horticulture and has worked in a variety of production nurseries, primarily as a propagator. She has also been responsible for a large homestead garden that included lawn care, fruit trees, roses and many other ornamental plants. More recently, Annette has concentrated on improving the garden landscape of the homes that she has lived in and focused a lot of energy on growing edible plants as well. She now enjoys sharing her experience and knowledge with others by writing articles about all facets of gardening and growing plants.


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