(Editor's Note: This article was originally published on May 16, 2008.)
Australia has a large number of mistletoe species, all of them growing as parasites on various trees and shrubs. Some 84 species are recognised, 70 in the Loranthaceae and 14 in the Viscaceae.
In the South-east of the country, much the commonest species is the Drooping Mistletoe - Amyema pendulum. This plant is a parasite of several Eucalyptus trees and several species of Acacia. It has also been found growing on several introduced plants including Hawthorn - Crataegus monogyna and some fruit trees.
The plant has long narrow leaves, perhaps a little like Eucalyptus leaves and the stems and leaves hang downwards, leading to its name of drooping mistletoe. The flowers are orange-red, borne in dense clusters in groups of three. They have a long slender tube, which is split in 5 almost to the base. Flowers can be found throughout the year, but mainly in the late spring and early summer.
The flowers are succeded by berries, brown as they develop, but ripening to off-white.
Drooping Mistletoe plant
Drooping Mistletoe stem
Drooping Mistletoe buds
Drooping Mistletoe flowers
A fully grown plant often has the form of an inverted cone hanging below a branch of its host plant and the plants are often very conspicuous, looking so different from their host.
Many people look on mistletoe as a pest species and claim that it will kill the tree it is growing on. Clearly killing its host would also kill the mistletoe, which cannot survive on its own. Some trees retain mistletoe plants for a great many years and show no sign of stress. It does happen however that one mistletoe plant often results in many more in its close vicinity and this can result in a tree getting to the point where it has more mistletoe leaves than its own leaf. An example is shown below of a Blackwood tree - Acacia melanoxylon, which has so many mistletoe plants, that the blackwood leaf is mostly obscured. When the tree is as overwhelmed with mistletoe as this, it may go into decline and eventually die.
Drooping Mistletoe berries
Drooping Mistletoe is attractive to birds and several species of honeyeaters visit the flowers in their search for nectar.
New Holland Honeyeater
The New Holland Honeyeater - Phylloptera novaehollandiae is one I have often seen at mistletoe flowers.
There is another little bird that plays a very important role in the life of this and several other Australian mistletoes. The Mistletoe Bird - Dicaeum hirundinaceum has a very close relationship with mistletoe plants. The Mistletoe Bird feeds mainly on the berries of the mistletoe and it is the main vector for distrubuting the seeds. Most birds perch across a branch or twig and as a result their droppings fall to the ground. The Mistletoe Birds always perch facing along a branch or twig and their fairly sticky droppings land on the branch and usually stick to it. This deposits the seed, with a dose of fertiliser and gives the new mistletoe plant a good chance of establishing itself on its host plant. This explains why when one mistletoe plant establishes in a tree it is quite common for additional plants to appear in the same tree as the Mistletoe Bird doesn't fly far between meals!
Here are the mistletoe birds:
Male Mistletoe Bird
Female Mistletoe Bird
We built our house on a clear block apart from a few mature Eucalypts, and there were no mistletoe plants in our garden for several years. We had planted a Black Wattle - Acacia mearnsii however and a Mistletoe Bird must have visited us, because a large Drooping Mistletoe soon developed. Since then additional mistletoe plants have appeared in a Blackwood - Acacia melanoxylon and a West Wyalong Wattle - Acacia cardiophylla as well as additional plants in the Black Wattle.
I spotted one plant in the Blackwood when it was very young (it subsequently grew to a full flowering plant).
Drooping Mistletoe seedling on a Blackwood branch
I also discovered an even smaller new mistletoe growing on a Melaleuca pustulosa, which is an endemic Tasmanian plant and Tasmania has no mistletoes. This may be the first ever mistletoe on Melaleuca pustulosa, but despite its healthy beginning, this one died without reaching its flowering stage.
We have a local park which attempts to display a lot of the local native plants and I wanted to establish mistletoe there. I came across some mistletoe with ripe berries and found that many of them has already germinated. I tried placing several of these on appropriate host trees in the park, but not one of them got started. Since then one mistletoe plant has appeared in the park, so a mistletoe bird must have paid the park a visit. He is much better at planting mustletoe than I am!
Having mistletoe in the garden is not just another attractive and interesting plan, it is also a breeding ground for other creatures. On one mistletoe plant in our garden, I found this cluster of yellow eggs:
Imperial White eggs
Baby Imperial White caterpillars
Imperial White caterpillars
Imperial White chrysalises
Imperial Whites emerging
Male Imperial White butterfly
Female Imperial White butterfly
I watched them hatch into tiny caterpillars, which fed communally on the mistletoe leaves and they grew into large purple-brown caterpillars. When fully grown, the caterpillars wove a large communal web in what was left of the mistletoe plant and turned into orange chrysalises. As the chrysalises matured they turned black and eventually a number of beautiful Imperial White - Delias harpalyce butterflies emerged.
The male butterfly has white upper wings with a broad black and white border, while the female is grey, but both have brilliant red and yellow markings on their underwings.
Mistletoe Moth on Buddleia Mistletoe Moth caterpillar on mistletoe
We have a Buddleia shrub beside our driveway and its flowers are very attractive to many species of butterflies (including the Imperial White). One day I found a large colourful moth feeding on the Buddleia and I found that it is known as the Mistletoe Moth - Comocrus behri. It is called Mistletoe Moth, because like the Imperial White it feeds its caterpillars on the mistletoe, and 2 years later I was delighted to discover a Mistletoe Moth caterpillar feeding on the Drooping Mistletoe leaves in our garden.
We are pleased that the Mistletoe Bird has brought mistletoe into our garden and delight in the birds, butterflies and moths that it attracts.