Tilde's Talks: New Zealand Mistletoe — More Than Just a Christmas Kiss
You loved Charlie’s Chats, but now we are introducing Tilde's Talks! Tilde Sorensen, a Waiheke local and a Te Korowai o Waiheke Field Team Technician, graduated from the University of Auckland in 2022 with a Master's in bio-security and conservation, specialising in monitoring invasive and native skinks on islands. She played a key role in setting up the stoat pilot on Waiheke Island in 2016 and is currently training to become a stoat detection dog handler.
Among the long list of mystifying Christmas traditions is that of kissing under the mistletoe. Historians cannot agree on when this tradition began or why it started. There is a possible link between the tradition and the story of Baldur in Norse mythology. The legend goes that Baldur woke up one morning convinced that every plant and animal on earth wanted to kill him. Baldur’s mother Frigg went to every plant and animal asking them not to harm him and they all agreed. Baldur received the news and was relieved, but just as he allowed himself to relax, an arrow pierced his chest. Frigg had forgotten to ask the unassuming mistletoe.
Loki, the trickster god, took advantage of this, making an arrow out of the plant and using it to kill Baldur. The gods managed to resurrect Baldur, and Frigg, in delight, named the mistletoe the plant of love and kissed anyone who walked beneath it. While a good story, the link to this myth is rather tenuous. It is more likely that at some point in history, a man came up with the idea for his gains and managed to convince everyone else to go along with it.
Frigg has not been the only person to overlook the mistletoe (or pirinoa) and the plant is unknown to many in Aotearoa. New Zealand is home to 8 different species, with habitats ranging from mountain beech forests to low-lying coastal forests. A ninth species is now presumed extinct.
The showy flowers are red or yellow and carpets of fallen blooms can sometimes be seen under trees. The plants are semi-parasitic, meaning that they are parasites on their host trees, digging their roots into the bark and stealing a small amount of the tree’s nutrients. Mistletoe also have leaves containing chlorophyll which means that they gain some energy through photosynthesis. The host tree offers the plant nutrients and raises them above the forest floor to a point where they can access light without needing to grow their own trunk.
New Zealand Mistletoe
The lifecycle of Aotearoa’s mistletoe species is fascinating. Pollination is mostly carried out by honey eaters such as tūī, kākā and korimako (bellbirds). The petals of mistletoe are spring-loaded and must be squeezed in the right way to open. A bird that grabs the flower in its beak and squeezes, will trigger the petals to open and expose a pool of nectar in the flower. Without the birds, the flower remains closed and unpollinated. Bee species may also activate the flowers but it is by bumping into them and they do not appear to have evolved to pollinate them. Once pollinated, the flowers will ripen into berries.
Birds are also responsible for spreading mistletoe seeds. Seed dispersal by berry presents challenges to an epiphyte (a plant that grows on trees). When relying on birds to deposit seeds, how can the plant ensure that the seed will land on the branch of a tree rather than dropping onto the forest floor? A seed that lands on the forest floor will not grow as there is little light and the plant needs the resources of a host tree. The answer is that when a seed passes through a bird’s gut, the outer flesh is stripped off, revealing an immensely sticky layer around the seed. This layer causes the seed to stick to the bird’s feathers or feet until it lands on a solid surface, where it will be transferred.
Mistletoe were once common in the New Zealand bush but have declined significantly. For a long time, it was thought that the decline was due to loss of habitat due to logging and the introduction of possums. Research by scientists Jenny Ladley and Dave Kelly in 2004, suggests that this is only part of the story.
Due to the mistletoes’ reliance on birds for both pollination and dispersal, the health of bird populations must be important for their survival. Predators such as rats, feral cats, hedgehogs, and stoats may be at least in part responsible for the decline without ever praying to the plants directly. A small-scale experiment in Craigieburn involved stoat trapping during the bellbird breeding season and resulted in higher fledging of bellbirds. The increase in bellbirds failed to increase mistletoe pollination over a single season but would likely help over longer timescales.
Waiheke was once home to Adams mistletoe which was last seen in 1954 and is now presumed extinct. Mistletoe are supported by an entire ecosystem, so protecting trees and trapping predators is important to their survival. Without the conservation work done by thousands of organisations and volunteers around the country, it would be easy for the remaining species to share the fate of the Adams mistletoe.
As we begin our Christmas celebrations, spare a thought for this interesting and endangered plant. If you go for bush walks, especially in native beech forests, look out for the telltale red or yellow flowers in trees or dropped on the forest floor. All sightings of mistletoe should be reported to DOC.
— Written by Tilde Sorensen
Bibliography
https://www.nzpcn.org.nz/flora/species/trilepidea-adamsii/
https://www.nzes.org.nz/nzje/new_issues/NZJEcol29_1_69.pdf
https://newzealandecology.org/system/files/articles/NZJEcol20_1_69.pdf
https://www.nzgeo.com/stories/the-mystery-of-the-disappearing-mistletoes/