1990s National Mistletoe Survey

A major project updating 1970s data

Much of what we know about mistletoe distribution in the UK comes from survey work by the Botanical Society of the British & Ireland (BSBI) in the 1970s and a follow-up project, jointly run by BSBI andPlantlife in the 1990s. The 1990s survey was coordinated by Jonathan Briggs, who now runs Mistletoe Matters.

Summary information is given below, followed by some commentary on regional studies since the 1990s and possible/likely change to mistletoe distribution in Britain.

Summary of 1990s survey results

The peculiar pattern of mistletoe across the country is immediately visible by mapping the survey results, shown in the banner image at the top of this page. Most of Britain's mistletoe is clearly concentrated in the south-west midlands, specifically the counties of Herefordshire, Monmouthshire, Worcestershire, Gloucestershire and Somerset. Apple trees came top in the survey as the favourite host tree, and gardens and orchards came top for habitat. The graphs below summarise the overall host and habitat data from the 1990s survey.

 

It was that preference for apple trees that initially prompted the 1990s survey - was the decline in traditional apple orchards, a traditional landscape feature of mistletoes SW midlands homeland, causing a similar decline in mistletoe?

Results, as you can see from the comparitive maps above, were not very conclusive. In distribution terms the 1990s pattern was very similar to the 1970s, with an apparent increased distribution in the east of Britain. But that distribution data hides information on quantity which, according to the views expressed in the survey, was changing with apple orchard loss. It would seem that mistletoe itself is not threatened and might even be thriving, but the Christmas harvest, from traditional apple orchards, might be endangered. The survey results were described in a joint BSBI/Plantlife report Kissing Goodbye to Mistletoe? written by Jonathan Briggs in 1999.

That report is, of course, not the end of the story. Why were there more records in the 1990s - was there better recording than in the 1970s or was there really more mistletoe in some areas? And is the mistletoe harvest from old orchards really threatened - in many orchards in mistletoe's main stronghold there seems to be even more than there used to be. But mostly only in very neglected orchards - which would suggest this is not a sustainable situation.

Those two key questions - about distribution change and about quantity available in orchards - are still unanswered but there is some information to work on. Some comes from the regional and local mistletoe survey projects mentioned above. These support the idea of distributional change, possibly linked directly or indirectly to climate change. As for the available crop from orchards, that continues to be a concern, and is one of the issues the current survey projects, particularly the mistletoe management in orchards project, are currently investigating.

For more information on all these issues visit our Information Sheets page where there are downloadable summaries on distribution, rarity and management/supply and links to some recent publications reviewing the issues.

Developments since the 1990s

Many regional, county-based and other local mistletoe surveys have been organised since the 1990s National Survey. Examples include surveys organised by county Wildlife Trusts (e.g. Norfolk, Herefordshire etc) and surveys of particular mistletoe populations outside of the main mistletoe areas (e.g. studies in Richmond, Essex, Cambridge and Dublin).

Some of these local studies have produced interesting and intriguing results, suggesting that mistletoe is spreading faster than usual in some relatively isolated eastern mistletoe colonies (particularly in Richmond, Essex and Cambridge). These results may simply be reflecting a natural increase in spread as mistletoe berry numbers increase (each plant produces double the number of flowers, and thereforedouble the berries each year, so accelerating spread might be normal) but, as some of these populations are already over a century old and have not shown this behaviour before, it may be that other factors are responsible.

One possibility is climate change - modelling using mistletoe's climatic preferences suggests that it will spread eastwards in Britain and northeast-wards in mainland Europe with expected climate change. So this could explain new spread in the east. An alternative and/or additional explanation is a change in bird vectors, which may themselves be due to climate change. Overwintering Blackcaps, which are very efficient mistletoe spreaders, have increased from a handful to many thousands in Britain in recent decades, and these birds may well be affecting mistletoe spread. More details on some of these issues are available in our Information Sheets.

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