Mistletoes – magical, mysterious, misunderstood and quintessentially Australian – part 1

Mistletoes are like exquisite earrings on native trees. This beautiful specimen is Drooping Mistletoe, Amyema pendula growing on Coast Manna Gum, Eucalyptus viminalis subsp. pryoriana. Photo Ellen White

Earrings on native trees

To the imaginative eye, mistletoes may look like earrings hanging gloriously at the outer edges of native trees, providing a brilliant splash of bling. Though, they mostly try to be discreet and blend in, like the most exquisite earrings, they do transform during the day with changes to in the natural light, and especially from month to month, as they transition from chandelier-like leafy splendour, to a delicate floral beauty, and ultimately to eye-catching, pendulous, fruity,  orbs.
  
Mistletoes are also a critical part of healthy Australian ecosystems, that hundreds of wildlife depend on for food and for shelter. Sadly, they have been maligned and misunderstood for nearly as long as non-indigenous Australians have lived here.  

Did you know that in 1904, native mistletoes were declared a noxious weed and for 50 years we tried to exterminate them from our woodlands and forests? Thankfully, we didn’t succeed, largely because of the dedicated work of a little Aussie battler, the tiny Mistletoebird and his career partner, the Painted Honeyeater.

But first, here are the ABCs of mistletoes, before we begin to explore the full mistletoe story.

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A Mistletoebird wiping the sticky fruit onto a branch where it will germinate. Click on the image to watch a facinating 3 minute video with David Attenborough.

The word mistletoe's quirky origin

Mistle-toe is from two Anglo-Saxon words, ‘mistel,’ for dung and ‘tan,’ for twig, which makes sense when you know that mistletoe seeds are spread by birds in their droppings onto the small branches of various host trees.

In Australia, the Mistletoebird and the Painted Honeyeater are the mistletoe specialists. They have evolved a technique to efficiently ‘plant’ the sticky seeds onto host-tree branches. It takes only 15 minutes for a meal of sweet berries to pass through the Mistletloebird’s modified gut. A quick wipe of its bottom on a suitable branch and there the seed sticks until it germinates. 

Then each seed sends out a ‘root’ that penetrates the bark of a branch until it reaches the sap-stream. Studies have shown that nearly 100% of the seeds germinate when they are expertly placed by Mistletoebirds and Painted Honeyeaters.

Mistletoe seeds then develop into woody plants that continue to ‘hitch a ride’ on their host for decades, taking water, minerals and nutrients. Mistletoe leaves photosynthesize their own sugars, so they're not fully dependent on their host, and are therefore classified as semi-parasites or hemi-parasites.
 
…and they do give something back to their host tree, as you will read a little later. 

Click on the Mistletoebird image to watch David Attenborough's very cute 3 minute video of the Mistletoebird doing its 'seed planting dance.'                                          

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Small, ripe Lychee-like fruit on the Wire-leaf Mistletoe, Amyema preissii.

First Australians valued mistletoe
 
Unlike the first settlers from Europe, Aboriginal and Torres Strait Islander peoples appreciated mistletoe for its food and medicinal values. For example, the berries of mistletoe were food for the Wadawurrung people from the Geelong, Ballarat, Werribee region of Victoria. They called it ‘Bal-yep’ (bal – to pound & yep – to eat), which suggests that they may have made a pesto-like mixture, with the seed and the soft fruit blended into a sweet protein-rich paste.

Among their favourites were the Wire-leaf Mistletoe berry, which looks and tastes like a miniature lychee and the Harlequin Mistletoe berry (Lysiana exocarpi) which is a sweet red berry about the size of a red current.

From central & western NSW, the Wiradjuri people called it ‘Wilburugil’ which may relate to the berries of the Box Mistletoe, Ameyema miquelii, that they called ‘Snotty Gobbles’ and ate like a natural chewing gum.
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Mistletoe foliage was ground into poultices to treat scabies and other skin conditions and the leaves were steeped in water to make a tonic for the common cold.

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The ecology of Mistletoe in a single image – from floral bling to berry to bird to bottom to branch to bud burst to beautiful mistletoe. Image. Surf Coast Nature Search

The diminutive and beautiful Mistletoebird

The male Mistletoebird has a bright scarlet-red chest, a glossy blue-black head and wings, with a white belly. Because it’s a member of the Flowerpecker family, the males have been nicknamed ‘Fire-breasted flowerpeckers’.

​The females, as often is the case in the bird world, are much more subdued with dark grey above, pale grey to white below, and no red chest.

The Mistletoebird’s nest is built within the mistletoe plant itself, from spider webs and flower blossoms to create a warm and cosy nook.

The Mistletoebird has formed a symbiotic relationship with mistletoe plants, so in exchange for its delicious fruits, the bird distributes the mistletoe seed. They tend to stay in areas of the woodland or forest where the mistletoe grows.

Other fruit eating birds also eat the berries and spread them further afield, though not nearly as efficiently, with far less seed successfully germinating on host trees.

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Getafix the Druid, demonstrating OH&S best practice, while harvesting mistletoe from a sacred oak tree. Original artwork by Albert Uderzo

Mistletoe magic

In the famous Asterix comic series, the village druid Getafix collects mistletoe to brew a magic potion that gives the Gauls superhuman strength.
In ‘Asterix the Gaul,’ Getafix explains;
 
"Here is the potion that makes the drinker invincible. It increases his strength tenfold for a limited period of time." (René Goscinny, 1959)
 
The druid made his magic potion from European Mistletoe, Viscum album, which is one of 4 species of mistletoe native to Europe and the only mistletoe native to Great Britain. This mistletoe is also famously known as the ‘kissing mistletoe’ with the belief that it will bring fertility and peace.
 
Getafix always harvested the mistletoe with a golden sickle during the winter solstice from a ‘sacred’ oak tree. Curiously, oak trees are an extremely rare host for this mistletoe species. It is usually found on apple, linden, poplar, willow and hawthorn, though some sub-species of European Mistletoe select fir and pine as their preferred host trees. Though European Mistletoe is not found in Australia we are one of the worlds hotspots for mistletoe diversity.
 
Compared to most of the world, Australia is rich in mistletoes with 97 species. DNA evidence indicates that the most diverse and colourful family of mistletoes (Loranthaceae) first appeared here, on the Gondwana supercontinent, 50 million years ago, so they are undisputably native to Australia.
 
Our indigenous mistletoes are hosted by over 4,500 species of flowering plants from 20 different plant families. 47 of these native mistletoes are found in southern Australia and 12 are found in Victoria.
 
‘Mistletoes are found throughout mainland Australia (not Tasmania). In forests and woodlands, deserts and heathlands. They also abound in urban and agricultural areas, making them some of the continent’s most cosmopolitan plants.
(David Watson, 2019. Mistletoes of Southern Australia. Second Edition)

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Southern Large Azure & Imperial White Butterflies on Box Mistletoe. Image from Mistletoe Propagation in Eastern Australia by Birdlife Australia

Mistletoe mystery – how it ‘punches’ well above its weight!
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Australian mistletoes have their own super-powers, and like Asterix the Gaul, they punch well above their weight. They are described by mistletoe expert Dr. David Watson as a ‘keystone species’ because so many wildlife depend on their nectar, their berries, and their nutrient rich leaves. If keystone species are lost, entire ecologies are likely to collapse, just like a brick-arch will crumble if its keystone is removed.
 
41 species of birds, mainly honeyeaters, have been recorded feeding on mistletoe flowers. The endangered Regent Honeyeater depends on them as a source of nectar and for nesting. Mistletoe nectar is highly attractive to butterflies and moths and other invertebrates. Brush-tailed Possums and Yellow-bellied Gliders have been seen feeding on mistletoe flowers. 33 bird species have been recorded feeding on mistletoe berries.
 
Many birds nest in mistletoe because it provides cool, dense shelter. Even Ringtail & Brushtail Possums use mistletoe clumps for daytime shelter and eat the nutritious leaves.
 
Many butterflies have developed a unique association with mistletoe. The larvae of Azure Butterflies and Jezabel’s depend on mistletoe leaves as their main food source. Genoveva Azure, Ogyris genoveva, caterpillars feed at night on Box Mistletoe leaves, while they are watched-over and protected by ants. The ants escort the caterpillars to their nest for safe shelter by day and are rewarded with the caterpillar’s sugary secretions.
 
For birds, possums and insects, mistletoes are natures air-conditioners, pumping out cooled air on hot days while providing a shadier environment. With warmer summers predicted, the densely branched clumps of mistletoes offer cool respite because they never stop transpiring and cooling the air around them. Unlike their host trees that conserve water on hot days by shutting down transpiration.

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The fleshy nutrient-rich leaves of Creeping Mistletoe, Meullerina eucalyptoides, with unripe berries, growing on Weeping Myrtle, Agonis flexuosa

Testing the ‘keystone species’ theory
 
‘Mistletoes are keystone species and an important feature of healthy woodlands and forests.’ (Watson, 2012)

David Watson led a radical 3-year study in 2012 to test this ‘keystone species’ theory. With the help of volunteers, he removed all the mistletoes from 17 native woodland areas of 44 box & gum grassy-woodlands in south-west NSW, to measure the effect on birds.

He found that the numbers of woodland bird species dropped by a remarkable 33%, and the total bird species richness fell by an extraordinary 20%. Rather than just the fruit-eaters and nectar feeding species, the group showing the greatest decline were the insect-eaters, especially those birds that feed mostly on the forest floor. 

This unexpected discovery was explained by looking more closely at mistletoe leaf-litter. Mistletoes produce a lot more leaf-litter than their hosts, and they concentrate the nutrients provided by the host tree, significantly increasing potassium, phosphorous, manganese and a range of other elements.

One study showed that trees with around 10% of their canopy as mistletoe, yielded double the amount of leaf litter over a 12-month period. This was particularly important for the build-up of litter under eucalypts that hold on to their leaves for 3-4 years.

Their companion mistletoes drop leaves within 1 year, providing a much quicker turnover of nutrients. An added boost for ground feeding insects, birds, and reptiles is that mistletoes shed leaves regularly throughout the year, whereas their host eucalypts and acacias, shed mostly in the summer. Therefore. mistletoes substantially increase the quantity and the quality of ground litter, so much so that a recent study found over 1,000 more insects per square metre when mistletoe is present. (Watson et al. 2022).
 
This is a link to the mistleitoe section of David Watson’s excellent website:
Follow his links to some facinating reading.

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The pendulous earrings of mistletoe dangling from native trees, may historically have been considered a high-end luxury item that the trees couldn’t afford, but fortunately bold research has shown them to be a ‘keystone species’ that countless wildlife depend on.

The question then arises, what is a healthy and sustainable number of mistletoes that a native tree can support? The answers to this enigma, as it is with many of the ecological challenges we face, will be found in patient observation.
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But there is much more to this fascinating mistletoe story, and that will be revealed in part 2.

Wire-leaf Mistletoe berries ready for propagation

What's next in Part - 2 of the mistetoe story;

• How mistletoes are being introduced into Melbourne's London Plane trees to help wildlife 
• Mistletoes are the 'canary in the coalmine' as they are a measure of environmental health - the Regent Honeyeater story
• Commonly seen species of mistletoe in Victoria
• Propagating mistletoes at home. 

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