“Mistletoe,” said Luna dreamily, pointing at a large clump of white berries placed almost over Harry’s head. He jumped out from under it. “Good thinking,” said Luna seriously. “It’s often infested with nargles.” – J. K. Rowling – ‘Harry Potter and the Order of the Phoenix’.

Mistletoe, Viscum album, growing in an apple tree.

It’s less than a week until Christmas, and it seems like a good idea – or at least a topical one – to write about Mistletoe, Viscum album.

Mistletoe is associated with the Winter Solstice and midwinter celebrations, specifically, the tradition of kissing under the mistletoe. Mistletoe plants are cut from trees, brought indoors and hung up. According to the WhyChristmas.com website, the original custom involved picking a berry from the sprig of Mistletoe and then kissing, until all the berries had gone. Nowadays the berries are left on the sprig, which is much more economical.

In continental Europe Mistletoe was regarded as a plant of peace and luck and in France it was often given as a Porte Bonheur (a gift for luck), at New Year, rather than Christmas.

The association between Mistletoe and kissing seems to date back to ancient beliefs about fertility, which are older than the Christian church. Mistletoe is an evergreen plant that grows mainly on deciduous host trees and provides a dramatic flush of greenery in the middle of winter amongst leafless boughs. Mistletoe’s shape may also be significant: its branches fork, it has paired leaves and its berries are full of sticky white juice – all suggestive of sexual organs in both shape and content. There are also links to the Ancient Greek story of Aeneas and the Golden Bough and the Norse legend of Baldur.

The kissing tradition may be in decline, which is a shame. A survey by a major British supermarket found that 71% of respondents under 35 had never been kissed under mistletoe, and only 14% of those surveyed had kissed under the mistletoe in the last year. But enough of kissing for now: Mistletoe is fascinating in lots of different ways.

Mistletoe, Viscum album, is a member of the Sandalwood Family, the Santalaceae. (It was previously considered to be in the family Viscaceae,  the Mistletoes.) It is a hemi-parasite. It needs to grow on a host plant for support, water and nutrients, but it has green leaves and manufactures its own sugars by photosynthesis. In the UK Mistletoe (subspecies album) can be found growing on several different tree species, including Poplars, Limes, Apple and Hawthorn. Mistletoe rarely grows on Oak, in spite of legends of druids with golden sickles gathering it from sacred oak groves, a story that seems to have originated with Pliny the Elder. In continental Europe, there are two more subspecies of Viscum album: austriacum grows on pine trees and abietis on fir trees.

Mistletoe is dioecious, with separate male and female plants. The males flower between February and April and produce clusters of insignificant flowers with four tiny petals in the fork between two branching stems. Female plants produce the familiar white berries in November and December.

Mistletoe berries are very sticky and are spread from tree to tree by birds, which eat the berries and remove the sticky seed by wiping their beaks against the bark of a tree. The scientific name of the Mistle Thrush, Turdus viscivorus, means “thrush that eats mistletoe”. Fieldfares also like the berries, but Blackcaps appear to be best at spreading them about. At one time Blackcaps were only found as summer migrants in Britain, but in recent decades continental birds spend the winter here, at the time that Mistletoe has its berries. As a result, the plant may be on the increase in the East of England. It seems to be particularly common in Common Lime and poplar trees in South Norfolk and we have some plants here in Norwich. (One can be seen when heading eastwards by train out of Norwich station; another is high on a tree on The Avenues, only hundreds of yards from my house.)

Once a Mistletoe berry has stuck to a suitable host tree, it forms a swollen holdfast. A stem and root-like haustorium grow out from the holdfast and the haustorium penetrates the host and starts to take water and minerals from its vascular tissue . Mistletoes are very highly adapted to their hemi-parasitic lifestyle. It is claimed that the germinating seeds of one species, Loranthus globosus,can ‘walk’ along a tree branch by flipping end over end until they become successfully wedged into the bark.

Mistletoe’s former stronghold was in apple growing areas along the Welsh boder, such as Herefordshire, though it has declined with the loss of our traditional orchards. Mistletoe is traditionally harvested and sold as a crop at Christmas time, and this harvest is beneficial because it stops the plant from becoming too vigorous. If left unchecked, Mistletoe reduces the productivity of its host tree, can cause stress in dry weather and may ultimately kill its host.

Mistletoe is locally common in the UK: Here are maps of Mistletoe distribution in the UK and worldwide. (The plant has been introduced to other parts of the world, including the United States.)

Worldwide, there are over a thousand species of Mistletoe and in Europe there are three more species of Mistletoe, as well as our Viscum album. The Red-berried Mistletoe, Viscum cruciatum, is found in southern Spain and grows on Olive trees, the Yellow-berried Mistletoe, Loranthus europeaus, is deciduous and grows on Oak trees and the tiny Dwarf (or Juniper) Mistletoe, Arceuthobium oxycedri, grows on Juniper. There are several North American and African species. A spectacular species from Western Australia, Nuytsia floribunda, is known locally as the Christmas Tree because it flowers in December. It grows as a free-standing tree but is nevertheless a hemi-parasite, with roots that reach out and take nutrients from nearby plants. When it grows near houses its roots will even latch onto underground electric cables and small irrigation pipes, causing damage (and even a short-circuit).

Mistletoe is poisonous to humans, though its toxicity is described as ‘slight‘ and the Plants For A Future website says that the ripe berries are edible (with caution). The active ingredients are viscotoxins and mistletoe lectins. Mistletoe poisoning can cause pale lips, inflamed eyes, dilated pupils, slow pulse, hallucinations and coma and may result in hepatitis. Mistletoe extracts have been used to treat stomach, lung and ovarian cancers and they are now marketed in Germany as ‘Iscador’ and ‘Helixor’, although their exact mechanism of action is still under investigation. Mistletoe has also been used to treat epilepsy, ulcers, high blood pressure and rheumatism and appears to have antiseptic, antispasmodic, astringent, digestive and diuretic properties.

If you want to grow your own Mistletoe, there are some great instructions and photos here.

The Mistletoe Pages website has lots and lots more information, plus free information sheets to download, posters and even a book about Mistletoe.