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Australian Grow Guide: Lemon Myrtle Tree (Backhousia citriodora)

The lemon myrtle is one of my all-time favourite plants. Nothing beats the lovely citrusy scent as you brush past this tree and the stunning display of large white pom-pom-type flowers.

Not only is this a beautiful tree or large shrub with its glossy green leaves and clusters of fluffy white flowers, but the leaves are commonly used to flavour all types of cooking.

Lemon myrtle is a rainforest tree and grows naturally in northern New South Wales and southern Queensland. It prefers to grow in a sub-tropical or warm temperate climate but it can tolerate light frosts.

Choosing a location and preparing the soil

Where you decide to plant your lemon myrtle will depend on your local climate. In hotter regions, it’s best to locate the tree in a more shaded spot especially if you have periods of hot, dry weather. Dappled shade is best for your lemon myrtle.

Backhousia citriodora Lemon myrtle 1 | Plant care

However, in cooler or milder climatic areas further south, you can position your lemon myrtle in full sun. If your area is susceptible to frosts, you are going to have to provide your tree some protection while it’s young and still becoming established. 

As lemon myrtles grow naturally in rainforest areas, you want to prepare your soil well by adding plenty of organic matter such as compost. These plants can adapt to most soil types but if you have heavy clay, you might need to add some gypsum to break down the heavy clay particles and open the soil up to allow better drainage.

Lemon myrtles can even be grown in large pots. Make sure that you use a premium potting mix and keep the plant well-watered during periods of hot, dry weather.

How to plant Lemon myrtle tree

Once you’ve prepared the soil, dig a hole to accommodate the root ball of the plant. It’s always better to make the hole twice as wide as this helps to loosen the soil and allows the roots to spread out. The hole should be around the same depth as the rootball.

hole for plant | Plant care

Then, all you have to do is take the plant out of the pot, tease the roots out slightly and place it into the prepared hole. Backfill the hole with the excavated soil and firm it down to secure the plant.

Water the newly planted lemon myrtle well as this allows the soil to settle down around the roots. Add a layer of mulch around the base of the plant. This helps to keep the soil cooler and retains moisture.

How to care for Lemon myrtle tree

Once your tree is well-established, it won’t require much maintenance. However, to encourage your tree to grow after planting, it’s a good idea to give it a boost with a dose of liquid seaweed every two to three weeks.

Once the tree is mature, it shouldn’t need additional fertiliser unless your soil is very depleted. However, if you replenish the organic mulch regularly, this should give the tree enough nutrients to sustain it.

Lemon myrtle Backhousia citriodora | Plant care
Backhousia citriodora / Photo by Krzysztof Ziarnek / Wikimedia / CC BY-SA 4.0

One thing that is vitally important is that you should ensure to give the lemon myrtle regular water. You should endeavour to keep the soil moist at all times during the warmer months of the year. However, you want to ensure that the soil is free-draining and doesn’t get waterlogged.

Once again, regular mulching will help the soil to retain moisture so this is very important.

Another thing you want to do while your lemon myrtle is still young is to tip-prune the new growth regularly. This will help to produce a more dense growth habit and a nicely shaped tree or shrub.

For mature trees, pruning is not necessary but you might want to do this after flowering has finished in order to keep your lemon myrtle looking neat and tidy.

Lemon myrtle problems, pests, and diseases

In general, lemon myrtles don’t suffer from too many problems if they’re growing in rich soil and are kept well-watered. However, while your tree is still young, you might want to keep an eye out for sap-sucking insects like aphids, spider mites, and scale.

These insect pests love tender new growth and will excrete a sticky sap that then facilitates the growth of sooty mould which can look quite unsightly. You can control these insect pests with an oil-based product such as neem oil. The resultant sooty mould can just be wiped off with a damp cloth.

Another problem to look out for is Myrtle rust. This fungal disease can be identified by the appearance of small lumpy spots with a reddish halo on new growth.

myrtle rust | Plant care
Myrtle rust / Photo by Scot Nelson / Flickr / CC0 1.0

If you spot any evidence of this disease, the first thing to do is to prune away the affected foliage and put this in the rubbish.

You can then spray your tree with an organic fungicide to kill off any remaining fungal spores. It’s a good idea to spray your tree again two weeks later.

What does a mature lemon myrtle tree look like?

Backhousia citriodora | Plant care
Backhousia citriodora / Photo by Krzysztof Ziarnek / Wikimedia / CC BY-SA 4.0

A mature lemon myrtle tree has a natural narrow cone shape with lovely glossy dark green leaves.

In summer, the tree produces masses of fluffy white flower heads. These are very attractive to butterflies, bees, and nectar-feeding birds.

Backhousia citriodora Lemon myrtle | Plant care

How to use Lemon myrtle for a hedge

To create a lovely dense lemon myrtle hedge, space your plants around 1 metre apart. Once planted, regularly tip prune in order to promote dense, bushy growth and keep your plants well-watered.

As the hedge starts to take shape, continue to prune regularly to maintain its dense growth habit.

Is there a dwarf Lemon myrtle tree?

As far as I know, there is no dwarf lemon myrtle cultivar available. However, with regular pruning, it is possible to restrict the growth of a lemon myrtle to a shrub size that is even suitable to grow in a pot.

‌FAQ

How big do lemon myrtles get?

Lemon myrtles can reach an ultimate height of 20 metres with a spread of around 5 metres. However, it is possible to grow this plant as a large shrub with regular pruning to keep it more compact.

Are lemon myrtle roots invasive?

No, lemon myrtle roots are not invasive.

Does lemon myrtle grow fast?

In general, lemon myrtles are not particularly fast growers. In fact, it can take around three to four years for them to reach maturity. This is one of the reasons why these trees can be kept quite compact.

Where can you buy a lemon myrtle tree?

You should be able to buy a lemon myrtle tree at your local garden centre or nursery and they’re also available in Bunnings.

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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