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Choosing the Right Fertiliser for a Hibiscus in Australia

Being a flowering plant, hibiscus needs a balanced fertiliser. Choose one that has plenty of nitrogen for lush green growth.

Growing hibiscus in Australia is a delight for many gardeners, especially when they come into full bloom.

However, it’s important to note that hibiscus plants are heavy feeders so to keep them looking their best, you need to fertilise them often in the warmer months when they’re in active growth.

What nutrients does hibiscus need?

Being a flowering plant, hibiscus needs a balanced fertiliser. Choose one that has plenty of nitrogen for lush green growth.

hibiscus hedge 3 | Plant care

Your chosen fertiliser should also have a good amount of phosphorus for healthy root development and a larger amount of potassium for good flowering.

The level of these nutrients is stated on the pack in a series of three numbers as N:P:K. The N stands for the nitrogen content, the P is for phosphorus and the K is for potassium.

While most fertilisers won’t have equal amounts of these, many will have higher amounts of nitrogen and smaller amounts of phosphorus and potassium.

Which fertiliser should you choose for hibiscus health?

Go to your local Bunnings, Mitre 10 or garden centre. You’ll actually find quite a lot of fertilisers that are specifically labelled for hibiscus and similar flowering plants such as bougainvillea.

Searles has a specialised hibiscus fertiliser called ‘Searles Hibiscus & Bougainvillea Fertiliser’.

The N:P:K of this granular fertiliser is 13.5 : 3.4 : 12.5.

This is ideal for flowering plants such as hibiscus and will promote lots of lush growth and flowering.

hibiscus hedge | Plant care

While this is a good, quick solution to keep your hibiscus looking their best, regular readers will know by now that I always look for more organic solutions.

This is because many formulated fertilisers can build up salts in the soil and can leach out into surrounding waterways if you have any of those around where you live.

My go-to fertiliser is Dynamic Lifter which has an N:P:K of 3.6 : 1.1 : 1.7.

This has a decent amount of nitrogen and phosphorus but not quite enough potassium for tons of blooms.

So, if you want to use this, you might need to supplement the potassium if your plants aren’t producing enough flowers.

Another alternative is to use a similarly natural product such as cow manure with an N:P:K of 0.6 : 0.4 : 0.5. This is about as balanced a complete fertiliser as you’re going to get.

Similarly, horse manure has an N:P:K percentage of 0.7 : 0.3 : 0.6.

You will also find that the compost that you make in your own compost bin also has an excellent N:P:K composition for flowering plants like hibiscus – 0.5 : 0.27 : 0.81.

What about liquid fertilisers for hibiscus?

If you prefer to use liquid fertilisers, then a good solution is Charlie Carp.

Charlie Carp | Plant care

This comes as either an all-purpose fertiliser which has an N:P:K ratio of 10 : 1 : 6 or a premium organic fertiliser with an N:P:K ratio of 2.0 : 0.4 : 0.75.

Of these two, I would use the all-purpose fertiliser because it has a higher ratio of potassium to nitrogen.

Another good solution is Seasol’s Powerfeed fertiliser. This has an N:P:K ratio of 12.0 : 1.3 : 7.0. 

Bear in mind that if you’re using a liquid fertiliser, you will have to apply it often during the warmer months because the nutrients will be available to your plants immediately and are not slow-release like granular or pelleted fertilisers.

For this reason, you should reapply them at least once a fortnight.

My tip for adding more potassium

If you have an open fire or a wood heater, don’t dispose of the ash in your rubbish because this is high in potassium.

Instead, scatter this on top of the soil around your flowering or fruiting plants in the garden.

Your hibiscus will benefit enormously from this but it does take a little while to see the results.

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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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