Some mistletoe species curiously resemble their host.
Mistletoes are parasites that invade their host plant. The seed of the mistletoe is deposited on the chosen host plant by a bird or aboral animal, when the seed germinates a stem called a hypocotyl emerges and grows into the tree’s vascular tissue, as it grows it conduct fluids and nutrients from the tree for its own use.
Many mistletoe species are host specific and will only grow from one species of plant. It is often difficult to recognise a mistletoe growing in a tree as some mistletoe species curiously resemble their host and remain hidden in their camouflaged mimicry of the host plant’s foliage ever so cunningly that they cannot be identified until they flower and fruit.
The flowers of mistletoe are often bright orange or yellow and when the colourful petals shed and fall to the ground they are easily seen and that can be the first time one is aware that a mistletoe has invaded a tree. A heads-up-look will quickly identify the source of the colourful carpet of petals.
Indeed some mistletoe flowers are so spectacular that a friend asked me the other day what was that spectacular, flowering, small tree with the orange flowers in my driveway?
He was shocked to learn that the tree - which was surrounded by insects and birds feasting on an abundance of flowers abundance - was in fact a Panama Berry, (muntingia Calabura), burdened with two large outcrops of mistletoe attached to its branches, the species Dendrophthoe falcata, a common mistletoe in Far North Queensland.
This species is not host specific and can be identified growing on a wide range of rainforest and orchard trees.
There are 92 varieties of the parasitic mistletoe native to Australia. Whereas mistletoe can be tolerated by many, large, native trees, a mistletoe infestation within an orchard can result in low to no crops of fruit.
A dense clump of heavy, water holding, mistletoe growing from the extremity of a tree’s branch adds weight making the branch susceptible to breakage during wind events.
Mistletoe grows very quickly on trees that are healthy, well watered, and fertilised, such as orchard trees.
In many cases the mistletoe will grow and fruit quickly in one season with birds spreading the seed to infect every branch of the tree. If control is not undertaken at the outset a small orchard tree will not recover from the onslaught.
The mistletoe’s vascular tissues around the attachment source grows runners penetrating within and along the branch of the tree.
The mistletoe can regrow from these runners, so it is recommended to completely remove the infected branch of the tree to be sure there are no nodes left for the mistletoe to regrow.
In dry eucalyptus country, fire is a natural control of mistletoe. Eucalyptus are fireadaptive and re-sprout after fires. On the other hand, mistletoe are fire sensitive and die after fire, cleansing the forest of the parasite.
The only way to remove mistletoe from a fruit tree is by the complete removal of the infected branch.
Within a natural forest setting mistletoes are a keystone species with a number of insects, birds and animals dependent on them. Birds are the main consumer and disperser of mistletoe fruit, especially the tiny mistletoe bird.
There are a number of marsupial fruit and leaf eaters who relay on the high water content of mistletoe leaves for food, especially in extended dry weather events.
Arboreal birds and animals discover that the seed of the mistletoe is not easy to excrete as it is covered in a sticky layer. It is amusing to watch a bird or marsupial twisting and turning and rubbing its anus on the branch until it is clear of the seed. The sticky seed quickly dries and sealed to the branch it germinates, then penetrates the tree to grow and loot water and nutrients from its host.
Cassowaries search the mangroves for snails and tasty fruits, when they discover the mistletoe in fruit they stretch high to harvest every ripe fruit.
It’s the end of the line for this seed as the cassowary expels its mangrove feasts on to the mangrove floor in a muddy acid bath of scat.
Mistletoes are host to a wide range of butterfly and moth species and other insects. The
spectacular Northern Jezebel, Azure and Union Jack butterflies’ caterpillars feed on the leaves of the mistletoes, Dendrophthoe curvata, D. Glabrescens and D. Vitellina and are dependent on these species for their life cycle with Jezebels and Azures feeding exclusively on mistletoe.
Possums, sugar gliders, twig beetle, and a range of other bugs and spiders rely on the succulent high water, and nutrient content, of mistletoe leaves for food and nesting.
The mistletoe flowers are particularly high in nutrient filled nectar and the critically endangered Regent Honeyeater favours the nectar of the mistletoe as well, the dense canopy formed by mistletoe leaves offer it a protective nesting site.
Aboriginal nations around Australia ate the nutrient rich mistletoe fruits and the leaves were used for a wide range of medical conditions including to ease menstrual cramps.