Lemon myrtle: fresh, fragrant & evergreen

Currently producing a mass of delicate creamy-white flowers at Auckland Zoo, this stunning specimen is Backhousia citriodora, the hero of our horticulture blog this month.

Backhousia takes its name from James Backhouse, an English botanist, archaeologist, and geologist and was named by German botanist Baron Ferdinand von Mueller. Mueller was the national director of the Royal Botanic Gardens in Melbourne from 1857 to 1873 and founder of the National Herbarium of Victoria, which led to him naming many of Australia’s endemic plants.

Within the Myrtaceae family of plants, the Backhousia genus includes thirteen known species, all of which are found growing in the coastal rainforest areas of New South Wales and Queensland.

More than likely, you’ll know this plant as the lemon myrtle, and if you crush the glossy green leaves in your hand they will release a pungent, distinct lemony smell. Used in essential oils, its lemon scent is said to be ‘more lemony than lemon’ due to a high citral content of 90-97%.

As with Rongoā (Māori traditional medicine) in Aotearoa, Australia’s Aborginal communities have long harnessed the natural world around them (including plants and seeds) as medicines, to treat a range of physical and spiritual ailments. For thousands of years lemon myrtle has been utilised for its medicinal properties as a powerful antiseptic for healing, as well as flavouring in ‘bushfood’ (traditional dishes) and for making fresh tea.

Sadly these plants are susceptible to myrtle rust, a fungal disease that attacks plants in the myrtle family including pōhutukawa, mānuka and rātā, so it’s good to be aware of what to look out for and how to best deal with it. First discovered in Northland in early May 2017, this fungus has now spread to the North and South Islands of Aotearoa.

Myrtle rust attacks a plants new growth - young leaves, shoot tips, fruits and flower parts. When a plant is first infected, the leaves will display tiny raised spots that range from brown to grey, ringed with red-purple halos, which then go on to produce a mass of yellow spores. If you spot it don’t touch it! Instead contact MPI through the hotline 0800 80 99 66 and take these steps.

Great for the home garden, this evergreen shrub, can grow up to 6 metres in height and will continue to produce flowers from summer through to autumn. It prefers to be planted in well-drained soils with plenty of organic matter and compost, and is not frost tolerant.

You can see the lemon myrtle at Auckland Zoo on the walkway from Galapagos tortoises to emperor tamarins – sit and admire it over a cold drink at our Old Elephant House café! Stay tuned for the next blog in this series and if you have any recommendations on plants we should cover or questions for our horticulture experts, flick us an email!