Discover Your Patch: Adelaide Nature Notes by Dr Sandra Taylor
The word ‘mistletoe’ refers to many different woody plant species that have the same life form. The distinguishing features of the mistletoe life form, in addition to a woody stem and branches, are evergreen leaves and, especially, the mistletoe’s unusual method of obtaining moisture and mineral nutrients. Trees and most other woody plants have roots that anchor them in the soil and absorb moisture and mineral nutrients from the soil. In contrast, a mistletoe’s stem is anchored to a branch in the canopy of a tree by a structure called a haustorium that sends root-like filaments into the branch in order to absorb moisture and mineral nutrients from the host tree’s sap. Because the mistletoe’s evergreen leaves allow it to manufacture its own organic nutrients by photosynthesis, mistletoes are classed as half parasites (hemiparasites), unlike wholly parasitic plants (holoparasites) that obtain all their nutritional needs from their host.
In ancient Britain, the first plant to be called ‘mistletoe’ (Viscum album) was used in winter solstice ceremonies because of its seemingly miraculous ability to remain green and produce fruit during the season when the host trees shed their leaves and become dormant. At Christmas, in Europe and North America, it is still customary to kiss for luck under a sprig of mistletoe.
Many Australians regard mistletoe as an exotic plant introduced from overseas and damaging to Australia’s native ecosystems. In fact, all of the 91 species of mistletoe that occur in Australia are native, and mistletoe is increasingly being recognised as a keystone component of Australia’s biodiversity because it provides food and shelter for a wide variety of native animal species, from possums, to birds and butterflies.
In Metropolitan Adelaide, the Harlequin Mistletoe (Lysiana exocarpi) has spread from its native hosts (mainly Acacia, Allocasuarina, Cassia, Eremophila and Santalum species) to exotic street trees and ornamental garden plants, including Citrus, Jacaranda, Lagerstroemia (Crepe Myrtle), Magnolia, Nerium (Oleander), Platanus (Plane Tree), Prunus, Quercus (Oak), Salix (Willow) and Schinus (Pepper Tree) species.
Winter and early Spring are the best times to spot mistletoes on exotic hosts that have shed their leaves at these times of year. You can contribute to our understanding of the distribution of mistletoes in Metropolitan Adelaide and other cities and share your sightings with other mistletoe spotters by posting your digital images and locational information on the BowerBird website. If you can identify the species of the mistletoe and its host, that would be a bonus.
Watson, D 2001, Mistletoes of Southern Australia, CSIRO Publishing, Collingwood VIC.