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Plant of the Month December 2017

Viscum album

When Bing Crosby sang about his plans to be home for Christmas- alongside the powdery snow and obligatory gifts, he also requested the presence of a semi-parasitic plant with poisonous berries. This would seem strange if it wasn’t already engrained so deeply in our culture. A plant with significance for a wide range of people including Pliny the Elder, ancient Druids, Pagans, Christians and of course all those hopeful romantics, we have fallen in and out of love with mistletoe for at least the last 2000 years. 

Mistletoe, or Viscum album, currently in the Santalaceae family, grows on mainly deciduous trees throughout most of Europe, central and northern Asia to Japan, south to North Africa. Common in central and southern England, it becomes harder to find north of Yorkshire. When looking for mistletoe, common host trees are apple, poplars and limes. It is sometimes confused with bird nests from a distance, however the plant appears rounder than most bird nests and not as tightly packed. Despite being an evergreen plant, it is in autumn and winter after leaf drop, that the masses of plant become visible high up in the trees.

For ancient Druids, it is said that they considered mistletoe growing on oaks as to be associated with immortality and believed it to be a cure for everything, possibly due to it rarely being found growing on oaks, which themselves were highly revered. It was also considered to make sterile animals fertile, which is possibly where our own associations with romance begin. However, it is unlikely that those at Christmas parties will be considering the viscous pulp of the berry and the belief that it was absorbed into an animal’s sperm and consequentially promoted fertility. 

Customs later existed for children to wear mistletoe around their necks for protection, despite the danger in poisoning them. The church banned the use of mistletoe due to the associations with Pagan beliefs. It is however the toxins that are of much interest today as possible anti-cancer agents. 

Shakespeare also mentions mistletoe, although just the once, and it reveals a reputation that mistletoe may have had as sinister, it is referred to as ‘Baleful mistletoe’ when Tamora and her sons visit a dark evil forest in Titus Andronicus.  

Seen much more commonly indoors than out during the festive period, leaves are opposite, growing in pairs 5-8cm long and 2cm across, with white translucent berries, each containing a single seed. The stems appear forked, growing additional sets of ‘forks’ each year, once established. Plants exist as separate male and females, each with insignificant flowers which are scented and thought to be insect pollinated.

Cluster of mistletoe berries

Squashed mistletoe berries

Should you want to grow your own mistletoe, all you will need is fresh seed and a host plant (ideally an apple, poplar or lime tree), but also a lot of patience as it can take at least 3-5 years for a plant to establish. The best time to collect and sow seed is February-March in the UK, and if you are worried about it being lost to birds, covering ripening fruit with fine nettling before Christmas will protect them. Seed cannot be kept for long, and certainly not in the dark (including the fridge) as the seeds are actively photosynthetic and will die without light.

Applying the seed

Sprig of mistletoe for kissing under

Once collected, the single seed from each berry can be squeezed out, which is covered in a jelly like substance called viscin, of which just a little (and not too much of) is needed and will help stick to the host and germinate later. Young tree branches (approximately 2-6cm in diameter) work best as hosts and will support the weight of the plant in years to come. Choose branches further away from the trunk and place 4-6 seeds at 10cm intervals along the surface. There is no need to make a cut into the branch, just firm seeds in place by pushing them gently against the bark. A label with the date will enable you to later locate the hopefully germinated plants. Applying numerous seeds will increase your likelihood of success as unavoidably some will be lost to birds or insects. By April, seed should have germinated, although very little growth will be seen in the first year. Small green shoots are a good sign and by the third year you should hope to spot tiny leaves, although this can take up to 5 years. Once the plants start leafing up, they will start to grow much quicker. 

There are a few myths regarding successful germination of mistletoe and are generally unhelpful, and some completely false. It is unnecessary for seed to be planted on the same species of host tree as it was collected from. Seed also does not need to be passed through a bird first in order to germinate and neither is bird droppings required. Seeds do not need to be held in place with a muslin, nor applied to old thick branches, and finally, never store your seed in the fridge.

This rather surprising plant is as historically interesting as it is biologically, and will no doubt be inspiring many more crooners to come, but will hopefully inspire future medical research too. 


Andrew Luke and Miranda Janatka Posted by Andrew Luke and Miranda Janatka

Andrew Luke is Head Gardener at Wrest Park (English Heritage). He can be contacted on Twitter @PlantGrafter
Miranda Janatka is a Botanical Horticulturist at Kew Gardens, she can be contacted at Twitter on @Miranda_J​

1 Comments To "Plant of the Month December 2017"

eddie On 18.12.2017
Thanks both, i enjoyed reading the article. It is always good to have myths exposed too - there are a lot of them in our line of work. Reply to this comment
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