This page introduces some aspects of mistletoe biology, including an explanation of what mistletoe is, a brief discussion about the many other mistletoes around the world and then an account of the hosts and habitats where European mistletoe Viscum album thrives in Britain.
For information on conservation status, distribution and biodiversity value visit the Conservation page.
What is mistletoe?
The familiar white-berried Christmas mistletoe of Europe is just one of many hundreds of mistletoe species worldwide. All are plant parasites, growing on tree branches (though a few grow on roots), and in their native lands many have similar folklore and superstitions to our own species.
Strictly speaking most mistletoes are only ‘hemi-parasitic’ as most have green leaves to photosynthesize and rely on their host for ‘just’ water and mineral nutrients. But the interaction is often more complex than this, with some exchange of metabolites between host and parasite vascular systems too. Many have peculiar pollination systems, and most have interesting insect and bird associations.
As parasites they do, of course, seriously distort and suppress the host branch they grow on. That’s not a problem if just a few branches are affected – but if the mistletoe becomes established on every branch it’s bad news for the tree and, ultimately, the mistletoe.
Mistletoes pose intriguing biological and evolutionary questions for the biologist, and sometimes problems for tree managers and foresters, but to most people they are only interesting for their traditions and folklore – especially the Christmas kissing tradition.
The native mistletoe of northern Europe, Viscum album, is at the core of most of the popular traditions and legends about mistletoe, including the association with Christmas, the Kissing tradition, and the ancient associations with Druids, Romans, Norse gods etc.
Other mistletoes around the World
There are about 1500 species of mistletoe around the world, and all of them are shrubby plants that grow parasitically on trees. Most grow in the tropics and subtropics, with relatively few species in northern temperate areas.
Exact numbers, and their botanical classification system, are both variable, depending on current fashions in botanical naming. There are, traditionally, two main mistletoe families, the Viscaceae (which includes our Viscum album) and the Loranthaceae, which includes many of the more colourful tropical species.
The Viscaceae is currently considered (under the current APG system) to be a subgroup of the much larger Santalaceae, or Sandalwood family. That family includes many other parasitic species as well as the former Viscaeae species.
Europe is at the edge of the mistletoe families’ range and so has only a few species. These are described briefly on the Conservation page here.
In North America there are several mistletoe species – primarily the leafy Phoradendon species, which are used, in the USA, as a substitute for the European Viscum at Christmas and the much smaller Arceuthobium species. These are the so-called dwarf mistletoes, with scale like leaves. They can be serious pest species of trees in forestry plantations.
Further south, particularly in Africa and Asia, there are many more mistletoe species, ranging in appearance from the showy-flowered loranth species to the more discreet Viscaceae types. The picture below is one of the loranths, Agelanthus sansibarensis, growing on a mangrove tree in a southern Kenyan coastal swamp.
There are Viscum species in Africa too. The two pictures below show how they vary in appearance.
Many more mistletoes could be described here, but this site is primarily about Viscum album – there’s more about that species below:
Viscum album hosts and habitats
Hosts in Britain
In Britain the commonest host for mistletoe is cultivated (not wild) apple trees. But it also occurs on many other tree species, with other favourites including limes, poplars, and hawthorns.
The full British host list runs to many hundreds of tree species, and our species of mistletoe (Viscum album subspecies album), is thought to have the widest host range of any mistletoe species in the world.
The graph above left, based on data from the 1990s National Mistletoe Survey, shows relative proportions on the most common hosts – the full list is very long and so if that graph had every species included it would continue to the right for many metres.
Habitats in Britain
Mistletoe’s main habitats, other than the obvious need to be on a tree, are worth considering closely. Despite needing trees mistletoe is not, generally, a woodland or forest plant, so it is a mistake to look for it there. Instead it prefers its host trees to be in open situations with plenty of light around the tree.
So favourite habitats include gardens, orchards, parkland (traditional and modern), churchyards etc. It is interesting to note that most of these are ‘man-made’ habitats – and that in Britain before widespread woodland clearance mistletoe would have been restricted to open areas and woodland edges, possibly mainly on natural boundaries such as waterside sites or cliffs.
There is a downloadable information sheet on hosts and habitats in the UK here.
European hosts & habitats
Viscum album’s hosts in Europe are similar to those in Britain – many possibles but some definite favourites (apple, poplar, lime etc). The main difference in mainland Europe is a wider host range, with mistletoe often seen on some species (e.g. Birch, Sugar Maple) that it is rarely seen on in Britain.
There are some more technical differences too, as there are more subspecies of Viscum album on the continent than in Britain. There are three in total, including the usual Viscum album subspecies album (this is the one we have in Britain) on the many deciduous hosts but also subspecies austriacum on pine trees and subspecies abietis on fir trees. A fourth subspecies (V a ssp creticum) is only found on Crete, also on pines.
Mistletoe habitats across Europe are, unsurprisingly, very similar to Britain, with much in gardens, orchards and other suburban habitats, and only found in woodland with fairly open structure, such as poplar plantations or, for the evergreen host species, the open forests of upland areas.