Director's dung on a twig

It's now long enough after Christmas for me to write about mistletoe without reference to northern European mythology or folklore, or to the kiss-inducing mistletoe, the European Mistletoe, Viscum album.

I will mention the anglosaxons though. It was them that came up with the word 'mistle', for dung, which when added to 'toe', for twig, aptly sums up mistletoe as dung on a stick. At least to start with. 

Fruit-eating birds distribute mistletoe seed in their droppings, or sometimes by wiping their beaks. The mistletoebird, a small bird with bold red markings, is the most common perpetrator, effectively propagating its own food crop.

Mistletoes are a much maligned group of plants. Perhaps because the term ‘parasite’ is seldom used in praise. In fact, mistletoes are semi-parasitic: they use sunlight to produce sugars like other plants, but get their water and nutrients from their host. In the case of the one featured here, a lot of water and nutrient...

There are over a 1000 species of mistletoe in the world (all belonging to the plant order Santalales), with about 80 in Australia. Most of them attach themselves to tree boughs, often mimicking the foliage of the host, but there are also root parasites such as sandalwoods, quandongs (Santalum) and the Ballart Cherry (Exocarpos). I've written before about the spectacular Western Australian Christmas Tree, Nuytsia, is a root parasite producing rich orange flowers in the heat of the south-western summer. 

Nearly all Australian ‘aerial’ mistletoes grow on a range of host species, but in look they tend to mimic their most common host. Some always grow on other mistletoes. The one I've featured here today is a massive Creeping Mistletoe, Muellerina eucalyptoides, growing on a Narrow-leafed Peppermint (Eucalyptus radiata) just near by daughter Em's home in Mittagong. Here are leaves of the mistletoe, then the peppermint. I've seen better matches but you get the idea.

Mistletoes are like any (semi)parasitic plant, maintaining some kind of balance in the ecosystem so that they thrive but so too do their hosts. It's not dissimilar to any dependency in nature. Too many kangaroos or koalas will damage and kill vegetation upon they depend. Too much mistletoe can do the same. 

Usually a tree will only die if already stressed. The added strain of supporting a heavy mistletoe infestation can tip a tree over the edge if already under drought or disease stress. Trees are unlikely to become draped with mistletoes unless they are already under some environmental pressure, or isolated from pack, as in this case on a roadside.

If you do want to remove  mistletoe, it's difficult. The simplest method is to saw off the supporting branch. Some people cover the mistletoe in black plastic and deprive it of essential sunlight (it’s only a semi-parasite remember). Although a selective herbicide is available, it is not particularly effective, but there has been research in the USA on a growth hormone that might help the host and harm the hostee.

Bear in mind that when you remove even a common mistletoe you risk loosing a whole ecosystem. Other rarer mistletoes might need this species to live on. Lots of birds rely on mistletoes for food and nesting – in arid areas mistletoe may be the most reliable source of nectar because they can flower all year. 

A horde of invertebrates thrive in mistletoes, including a number of butterflies and moths that depend upon mistletoe during their caterpillar stage. The brushtail possum is a frequent diner, and is perhaps one of the major controls to a population explosion of mistletoe in parts of Australia.

If you are mistletoe fan, you can encourage them to settle - but it’s hard work! You need to press the sticky seed to a branch in a sunny spot, where the bark is not too thick. Although the seed will often germinate, most mistletoes may not advance much further. Perhaps they miss their companion birds, or at least a tour through their gut. Still, the City of Melbourne, is actively spreading mistletoe through the streets of Melbourne with some success.

You could do worse than start with the Creeping Mistletoe, which is found naturally across much of eastern Australia and grows on various eucalypts as well as introduced plants such as oaks, birches and peppercorn trees. Its genus, Muellerina, is one of 65 in the plant family containing most, but not all mistletoes, the Loranthaceae; all four species are all found only in Australia. 

Oh, and the genus is named after Ferdinand Mueller who, as you know, was the first director of Royal Botanic Gardens Victoria.