This page covers geographical distribution of mistletoe, primarily Viscum album in Britain but also looking briefly at distribution abroad, and at some other mistletoe species in mainland Europe. Contents down the page include
Where does mistletoe grow? For the traditional mistletoe of Europe the answer is across much of continental Europe, petering out as you move further north, with discrete colonies confined to particular areas.
For other mistletoe species the answer is much more complicated, – the little map on the left gives a broad indication of where all the members of the two main mistletoe families live – all 1500 or so of them. You’ll spot that most are in the tropics and southern hemisphere, with relatively few in the north.[space]
In Britain most mistletoe is found in the south and west midlands, with particularly good populations in Herefordshire, Worcestershire, Gloucestershire, Gwent and Somerset.
There is mistletoe elsewhere, particularly in the south, plus a few rare occurrences in north and east England, Wales, Scotland and Ireland.
But it is only regionally abundant in that core area of the south-west midlands. Many assume this to be somehow linked to apple orchards (apple is a favourite mistletoe host, and orchards a favourite habitat). This assumption is almost certainly incorrect – there are many apple orchard areas elsewhere in Britain that don’t have mistletoe, and studies across Europe link mistletoe distribution to particular climate preferences, which do seem to match the main distribution in Britain.
You can see some clear climatic preferences, particularly altitude, in the detailed enlargement on the right. The line of the Cotswold escarpment forms the main eastern edge to the mistletoe area, whilst on the western side the valleys of the Rivers Wye and Usk can be traced as lines of mistletoe records, taking mistletoe towards the Welsh uplands.
The northern boundary of the area is formed by the Clee Hills (north-west) and the Birmingham plateau (north-east). The central empty area is the upland area of the Forest of Dean – good proof that mistletoe, despite loving trees, isn’t fond of woodland.
Much of what we know about mistletoe distribution comes from survey work co-coordinated by the Botanical Society of Britain and Ireland (BSBI) in the 1970s and a follow-up project, jointly run by BSBI and Plantlife in the 1990s. Data from both periods are shown in the small maps on the left.
The 1990s survey aimed to assess whether the decline in traditional apple orchards was affecting mistletoe too – was mistletoe declining? Results were mixed – orchard loss is affecting mistletoe abundance, but distribution patterns remained broadly the same as before. Indeed the new data suggested more mistletoe in the east and south-east, though that might reflect better recording effort more than real change – though there may be change in future, and it may have started already:
In the last 10-15 years there have been several reports suggesting that mistletoe is spreading faster than it used to in Britain. This is particularly noticeable in eastern areas, where established mistletoe populations, whilst often long-established, have previously seemed slow to spread as they are outside their climatic comfort zone.
Something is changing though – as many of those previously static mistletoe colonies are shifting. It could be subtle hints of climate change – computer modelling does suggest that mistletoe will head east with climate change. Or it could be something else.
One possibility is better spread of the seeds by Blackcaps, a bird species that is particularly efficient at spreading mistletoe. British Blackcaps migrate for the winter so they do not, usually, affect mistletoe here. But in recent decades continental Blackcaps have started overwintering in Britain, with many thousands now spending their winters here. Perhaps mistletoe is spreading more because of their activity.
Since the 1990s National Mistletoe Survey, which investigated whether mistletoe in Britain was threatened by the ongoing loss of apple orchards (its favourite habitat) there has been a widespread general belief that mistletoe is rare.
And yes, mistletoe in Britain is, generally, rare. There is very little in most parts of the country, and it is only abundant in the south-west midlands. But, as discussed on above, that relatively rarity in much of Britain may be to do with climatic preference – it shouldn’t be mis-interpreted as a decline.
Any decline due to apple orchard loss is only likely to be detectable in the south-west midlands where both mistletoe and apple orchards are abundant. There is certainly ongoing loss of both (mistletoe and apple orchards) in this area and that is an ongoing cause for concern – but it is, arguably, ‘just’ a significant decline in abundance not a threat to the species per se.
There are other factors to consider too, especially in areas outside mistletoe’s main range. In those areas it is commonest in garden and parkland habitats, and unlike apple orchards there’s no threat to these habitats. Evidence does suggest mistletoe is increasing in these areas and habitats.
Plus there’s the management factor – in older apple orchards in the main mistletoe ‘zone’ some mistletoe-bearing trees are becoming so neglected that mistletoe is increasing dramatically. This is only a short-term gain though – those neglected trees are dying and will be gone, taking their mistletoe with them, within a decade or two.
Factoring in biodiversity and commercial issues complicates this further. The biodiversity value of mistletoe is considered relatively high, with several dedicated species relying on it. But it isn’t known how much mistletoe is optimal for these species – with some evidence that they survive well in isolated mistletoe colonies and might dislike crowded mistletoe-laden trees.
From the commercial angle the ongoing loss of mistletoe in apple orchards is significant, as most of the Christmas mistletoe comes from these sources (it is not usually abundant enough or sufficiently reachable in other habitats and hosts).
So, drawing general conclusions for the whole country is difficult. There are several key points to consider, including;
- mistletoe is rare or scarce in many areas
- mistletoe is abundant, sometimes unsustainably so, in others
- mistletoe quantity is declining alongside apple orchard loss
- loss of apple orchards only really affects mistletoe in its core growing area
- mistletoe distribution is not affected by apple orchard loss
- mistletoe distribution may be changing, possibly increasing
- optimal quantities of mistletoe for maximum biodiversity is not yet understood
- loss of apple orchard mistletoe will reduce the seasonal mistletoe crop
In mainland Europe mistletoe is much more widespread, occurring across most of the continent and spreading eastwards well into Asia.
Distribution here also depends on subtleties of climate, and the absence of mistletoe in the Netherlands, northern Germany and most of Scandinavia reflect mistletoe’s climatic requirements. Small colonies occur in those areas but, like the isolated eastern colonies in Britain, tend to be fairly static.
A complicating factor for traditional mistletoe, Viscum album, in Europe, is the presence of additional subspecies. In Britain we have Viscum album subspecies album – a plant that only grows on deciduous hosts. But on the mainland this is joined by subspecies austriacum and subspecies abietis which only grow on evergreens (pines and firs respectively).
Plus, further south in Europe, some other mistletoe species begin to be found – these are outlined below:
1: Red-berried Mistletoe
As well as those subspecies of Viscum album there is one other full species of Viscum in Europe – and that’s the Red-berried Mistletoe, Viscum album.
Apart from the berry colour this mistletoe is similar to the familiar white-berried species, and grows in similar habitats – often on Olive trees.
In distribution terms it is very limited, being found only in Iberia, and mostly in Spain.
2: Yellow-berried Mistletoe
This is particularly peculiar, in comparison to the familiar white-berried species because of two key factors. Firstly it likes (actually prefers) oak trees as hosts – whereas the traditional northern species is so rare on oaks that those oaks are considered special and held scared (allegedly) by the druids. But this is common on oaks.
Secondly, it is deciduous. So, for this species at least, those special properties of ongoing life through the winter months, doesn’t apply – it loses its leaves at the same time as the host.
This species has a wide distribution across central southern Europe.
3: Dwarf Mistletoe
The last of the mainland Europe mistletoes is another oddity – our only representative of the Arceuthobiums or Dwarf Mistletoes. These are species with reduced leaves, almost holo-parasitic on their hosts and they are major forest pests in North America.
Our species doesn’t cause much damage, not least because it only grows on Juniper trees and bushes.
And it isn’t very widespread. occurring mainly around the Black Sea and parts of the Adriatic and Mediterranean.