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Scientific survey reveals the future of British bluebell woods is under threat

A  comprehensive survey reveals the future of British bluebell woods is at risk of cross-fertilisation with increasing non-native varieties that are spreading from gardens to the countryside.

Hyacinthoides non-scripta (bluebell) in woodland (Image: Peter Gasson)

The British bluebell wood is one of the most glorious of botanical marvels. Nowhere else in the world do bluebells bloom in such profusion: half the global population of Hyacinthoides non-scripta is found in the British Isles.

Under threat

In recent years alarm bells have sounded as ornamental bluebells – larger Spanish relatives of our native species, and various hybrids – have spread from gardens into the countryside. Quite how and when these introduced, or alien, plants got into the British countryside remains a mystery.

‘It seems very likely that most of the aliens out there have been planted or dumped, and that repeated deliberate introductions are still the main route,’ says ecologist Deborah Kohn of the Royal Botanic Garden Edinburgh, who recently completed a comprehensive survey of a representative slice of the British countryside.

Conservationists suspect that these vigorous incomers are still expanding their range and might ultimately out-compete and replace our native bluebell or erode its genetic integrity through interbreeding. But how worried should we be? Do natives and non-natives actually occur together in the wild, or do they occupy quite different haunts?

Bluebell Survey results

To find out, Kohn and her colleagues looked at the distribution of bluebells across south-central Scotland. Their survey took in traditional bluebell territory such as woodlands, riverbanks and road verges, as well as urban Glasgow and Edinburgh.

The good news is that 99 per cent of the bluebells they recorded turned out to be natives. ‘At the moment the distribution of aliens is still closely tied to the built environment,’ says Kohn. Aliens rarely appeared on heathland or conifer plantations distant from urban areas, or in remote coastal, boggy and acidic habitats.

It’s too soon to call off the alarm, however, because the aliens are probably still on the move. ‘Because the naturalisation of the alien species is a relatively recent phenomenon,’ Kohn explains, ‘their current distributions probably do not reflect a natural equilibrium with the environment.’ So far, their spread doesn’t seem limited by climate, as Spanish hybrids grow even in Shetland.

Cross-fertilisation of native and alien bluebells

Direct competition for space isn’t a problem at the moment – only 10 per cent of native bluebells were found growing alongside non-natives. Cross-fertilisation of the natives and aliens appears to be a serious worry, however. The survey found that more than 40 per cent of natives grew within about a kilometre of aliens, close enough to pose a significant risk of hybridisation.

Gardeners can take action

Kohn admits that it would be hard to get rid of what’s already out there. ‘But if people would stop putting alien material out into the countryside, that would limit the damage – and what’s there might eventually die out.’

Author: Gail Vines

Kew magazine
 

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