Fertilising Gardenias in Australia: Expert Tips

Gardenias appreciate well-drained soil that has been enriched with lots of organic material.

Who doesn’t love the heady scent of flowering gardenias in the garden? But, to get plenty of those lovely white blooms and healthy thriving plants, you will need to fertilise your gardenias.

Gardenias are fairly heavy feeders and they need nitrogen for healthy green foliage, phosphorus for a strong root system, and potassium for plenty of gorgeous blooms.

What type of soil do gardenias like?

Before we look at the best fertilisers for gardenias, we need to ensure that they’re growing in the right type of soil.

Gardenias really appreciate well-drained soil that has been enriched with lots of organic material.

Soil 1 | Plant care

The soil should also be slightly on the acidic side if you want your gardenias to thrive. The ideal pH range should be between 5.0 to 6.0.

If you’ve added plenty of matured compost to the soil, you should find that the pH level is just right.

Using a fertiliser regularly that is specifically formulated for acid-loving plants will also help to keep the soil at the optimum pH level.

In addition, you can use natural products such as coffee grounds around the base of the plant to help keep the soil acid.

What is the best fertiliser for gardenias?

Because gardenias need all three essential macro-nutrients (nitrogen, phosphorus, potassium) and also a good dose of micro-nutrients such as iron and manganese, you should feed them with an organic fertiliser such as Dynamic Lifter.

dynamic lifter | Plant care

Do this every two to three months from spring through to autumn. 

You can also use cow manure if you’ve enriched the soil with some compost before planting. Cow manure helps to put body back into the soil and is ideal for acid-loving plants such as gardenias.

If you prefer to use a liquid feed, choose something like Yates Thrive Roses & Flower Liquid Plant Food and apply this weekly during spring, summer and autumn. Liquid feeds will be taken up by the roots of your gardenias immediately.

How to fertilise gardenias

You can either use a pelleted fertiliser that you spread around the base of the plant and water in or you can liquid feed your gardenias by mixing a liquid plant food with water and applying this to the plants on a weekly basis.

If using liquid plant food, apply this to the base of the plant so that it gets straight down to the roots.

Gardenia Hedge 3 | Plant care

Liquid plant food is usually available to the roots immediately upon application and doesn’t remain in the soil. That’s why it’s important to reapply this weekly during the growing months.

On the other hand, pelleted organic fertiliser such as Dynamic Lifter is a slow-release fertiliser that the plant will take up as it’s needed. Therefore, this only needs to be applied once every two to three months.

Make sure that you water this in so that it gets down to the roots of the plants.

Fertiliser 1 | Plant care

Is Seasol good for gardenias?

Seasol is good for almost every plant in your garden. This is because it’s a soil conditioner and helps to strengthen the cellular structure of your plants.

Liquid seaweed products like Seasol also help to acidify your soil and gardenias really love this.

seasol bottle 4 | Plant care

However, to give your gardenias an additional boost, you might like to replace the regular Seasol with either Seasol Plus for Roses and Flowers or Seasol PowerFeed Pro.

These products contain important nutrients that flowering plants need which standard Seasol does not.

gardenia 2 | Plant care

If you are going to use the nutrient-fortified liquid Seasol products, you won’t need to apply any other type of fertiliser because these contain adequate amounts of all the nutrients that your gardenias are going to need.

Epsom Salts for Gardenias

Epsom salt is great for gardenias because it contains lots of magnesium. This will stop the leaves from turning yellow and give your plants a nice boost.

Epsom Salt | Plant care

You can read more about how to use Epsom salts on your gardenias here.

Basically, all you need to do is to mix around one tablespoon of Epsom salts with around four and a half litres of water and pour this around the base of the plant.


What soil ph is good for gardenias?

Ideally, gardenias need a slightly acidic soil with a pH level of around 5.0 to 6.0.

What is the best mulch for gardenias?

Because gardenias prefer acidic soil, the best mulch to use is composted woodchip or even sawdust.

Photo of author

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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