Going toe to toe with mistletoe

18 December 2020 7 minute read

Mistletoe (Viscum album) certainly has a celebrated role in the Christmas festivities - many folk hang up a green sprig in their houses as part of their yearly traditions. But what is it, where does it grow and how did it end up associated with kisses?

By Gurnam Bubber

A demure plant so in demand once a year, you can easily walk past and miss it.

Mistletoe has a lot more going for it than just being a spark for romance. It may surprise you to know that this favourite of would be Romeos is a parasite or more accurately is hemi-parasitic. It provides some of its own energy through photosynthesis but it also depends on taking water and nutrients from living trees. It’s a parasite that lives on tree branches and unlike ivy which gets all the bad press (see our Ivy article) it can weaken and damage trees.

It can’t survive in the earth but high up in the canopy it sends tiny roots into the bark to take in water and nutrients, slowly depleting the tree. A mature tree can cope with a small amount of mistletoe no problem, but if it spreads too much the tree may become depleted and be at risk of dying. In this case, the mistletoe can be managed so that both plants are kept healthy.

It’s important to note that Ecologists actually view mistletoe as an important part of a healthy ecosystem. The berries are a major winter food source for birds, who also find the dense foliage useful for nesting, even the dead trees are an important part of the ecosystem providing food and habitat for many creatures. Studies have shown that areas where mistletoe has been cleared have a significant decrease in the populations of birds and other species.

There are over 1,000 species found throughout the world and they have evolved to plant themselves on hosts ranging from pine trees to cacti. In the UK we have only one mistletoe species, European mistletoe (Viscum album). It’s the species most commonly associated with European-based mistletoe mythologies (like kissing beneath it on Christmas) and are typically found on large deciduous trees.

The best time to spot mistletoe is in the winter when the trees are bare of their greenery. It looks like a ball of tangled twigs from a distance, often quite high up in the branches. Once you’re closer you can see the pale green colour and in the winter and spring its milky white berries that are part of the festive look. These berries mature fully in spring and are poisonous to humans and many animals.

So how do they get up there? If the berries fell to the ground they wouldn’t be able to sprout, they need to get up into the heavens and perch on a branch. The berries contain a very sticky substance called viscin which helps the seeds to stick to the branches. The berries are a favourite wintertime snack for birds, who help to spread them when they poo out the seeds on branches high up in trees where they roost. This was also the source of its English name. Having noticed that mistletoe often sprouts from bird droppings on tree branches, the words for dung in an Anglo Saxon dialect—“mistel”—and twig—“tan”— were conjoined, and the mashup “misteltan” evolved over time into “mistletoe.” Another method for spreading is when birds wipe their bills on twigs and branches leaving behind the seed.

The pearlescent berries are enjoyed by many creatures including blackcap, thrushes especially the appropriately named mistle thrush and even occasionally squirrels.
There are a few insects which are only found on mistletoe, including the mistletoe marble moth (Celypha woodiana) who needs this unusual plant to complete its life cycle. Its larvae overwinter in small mines chewed into the leaves of the plant, which become inflated by late spring when the larvae are fully grown. The larvae then emerge from the mines and pupate in a cocoon under bark or among lichens on the host tree.

The mistletoe marble moth is rare and needs conservation in the UK, it’s populations are declining. It is thought that the amount of mistletoe harvested poses a threat to the future of this already rare species.

If you’re not completely convinced about the value of mistletoe, it has benefited humans as well as wild animals. There is evidence suggesting some mistletoe species may be useful in the treatment of cancer – in some parts of the world it's been used for this since the 1920s. The theory is that mistletoe therapy reduces the side effects of chemotherapy, improving quality of life and helping patients better tolerate the treatment.

Now is a good time to go in search of this wonder plant, but where to look? It can be found on a variety of host trees including apple, lime, poplar, sycamore, ash and hawthorn. It has been particularly popular in apple orchards. Its strongholds include Wales, the West Midlands and the South of England, with particularly large populations in Gwent, Herefordshire, Worcestershire, Gloucestershire and Somerset. You can still find the odd bit of mistletoe hanging around in other parts of the country too, so worth keeping an eye out for it, even in built up urban places like London.

Despite growing on trees, mistletoe is not generally found in a woodland setting, preferring hosts in open situations with plenty of light. You’re more likely to see it in gardens, orchards, parkland and even churchyards.

There is much folklore associated with mistletoe including the popular tradition of kissing under it at Christmas. Links and traditions associated with mistletoe date back to pre-Christian days. It also features in Druidic, Norse and Greek mythologies and has wide-ranging relevance to many cultures.

In the Middle Ages, it was believed that mistletoe have a variety of magical properties such as stopping the trances of epileptics and keeping witches at bay / warding off evil.

One of the most famous legends concerns the Norse god Baldur, who was considered invincible until an unknown assailant finally killed him with an arrow made from mistletoe. Separately, in an ancient Celtic ceremony, Druids would climb an oak tree to fetch some mistletoe to make an elixir that was said to cure infertility. Mistletoe was associated with peace as well as fertility.

While in the UK we associate mistletoe with Christmas, other countries link it more to New Year. For example, France sees it as a good luck charm and French people often give it to friends as a New Year gift to wish them luck in the coming 12 months.

So back to the most important question, how did mistletoe become entwined with romance? The short answer to this question is there is no one simple reason!

The UK tradition of kissing under the mistletoe is thought to have started in the 1700s, but it became much more popular throughout the 1800s. The Victorians especially became big fans of puckering up under the plant. The plant has been linked to so many stories and traditions over hundreds of years, and different people see it in different ways. Ancient Norwegian and Scandinavian tales agree that mistletoe has meanings of love and friendship.

It seems that mistletoe’s association with fertility and ritual and wintertime slowly morphed into the modern Christmas tradition. It makes sense that mistletoe, with its evergreen foliage would be brought indoors as decoration during the barren winter months, just as people do with fir boughs and holly branches.

Growing your own, yes it is possible! If you’d like your very own ancient symbol of peace and fertility the RHS provide some guidelines on how to seed trees you may have in your garden. You’ll need some patience as it can take plants 3 to 5 years before they can produce berries. In the meantime next time you’re out and about take a peek at the bare wintry trees and see if you can spot your very own mythical mistletoe.

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