Palms, a reliable climate change indicator in Europe

Lovingly tended to as far as Kristianstad in Sweden, palms have never had it so good in Northern European gardens. The UK, which has not had a seriously cold winter for about 10 years, is a case in point. A specialized nursery called the Palm Centre in Richmond, just outside London, claims to sell 50,000 imported palms a year, which then go on to be planted all over the country, way up to the West coast of Scotland.

It’s not just that the British have always been slightly fanatical about gardening. The fact is, quite apart from having become fashionable over the past decade, palms seem to have become a reliable indicator of climate change in Europe. The research coordinated by plant ecologist Dr. Gian-Reto Walther from Bayreuth University in Germany within the ALARM project proved that Trachycarpus fortunei palm seeds can germinate and survive in the wild as far as Scandinavia and Germany, despite some losses due to the harsher winters there. In England, Ireland and France, the seeds scientists planted grew surprisingly well in the native forests.

It remains to be seen whether palm-mania in Northern European gardens will end up becoming a biodiversity-enriching agent in itself, with seeds spreading beyond in semi-wild conditions. Given the rising temperatures, they well might, although some scientists rule out any overly aggressive colonisation of the surrounding landscape.

Stories of cold-hardy palms growing from Scandinavia (http://www.scanpalm.no/kristianstad_english.html) down to the German Blackforest populate the message boards of The European Palm Society, a branch of that International Palm Society that gathers palm enthusiasts and scientists alike. As if to confirm a fresh focus on Northern Europe, EUNOPS (www.eunops.org), an informal association of biologists with a wide spectrum of research interests in palms, have scheduled their next meeting for April 25-26 at the Royal Botanic Gardens in Kew, an outer suburb of London.

The British capital has always been a bit of an exception, since the warmer microclimate created by the river Thames has allowed a prized specimen of Phoenix Canariensis to grow for the last 150 years bang in the middle of Chelsea Physic Garden. Dr John Dransfield, honorary research fellow at the Herbarium in Kew, points to the difference between palms that fruit in Northern Europe, like the population around Lake Locarno, in Switzerland, which has been flourishing since the 1970s, and those which don’t. “I would use the concept of “spreading” to natural vegetation with caution, because I cannot envisage palms reproducing aggressively in Northern climate conditions”, he says.

But Trachycarpus likes an oceanic climate quite a lot, Dr Dransfield says. And he quotes the British examples of Abbotsbury and the West Coast of Scotland. Also, he adds, “here, in Kew Botanic Gardens, Trachycarpus is doing quite well outdoors”.

As far as palm nurseries go, there are some “in Holland, Belgium, Denmark and Sweden”, says grower Toby Shobbrook from the Palm Centre in Richmond, England, which sells about 15 species of palms that can grow outside, including Chamaerops (which is also the title of the Palm Society magazine, Ed.) and the Chilean wine palm. “Most of these palm trees are imported”, he adds. “There is certainly a greater availability of palms on the market in Northern Europe nowadays. The most common in this part of the world is Trachycarpus, one of the most cold-hardy species there is. In the UK, especially, I think it’s certainly feasible to have a population spreading naturally in semi-cultivated conditions: we have quite a few around here already. We growers know haven’t had a really cold winter for about 10 years and people get more confident in experimenting with borderline plants such as palms”.

The UK seems to have the biggest number of palm enthusiasts after Spain, Italy and France, Mr Shobbrook says. “We have a lot more growers here, as far as the West coast of Scotland, than in Holland, Belgium or Sweden, as the climate is slightly milder. There are probably tens of thousands of gardeners here in the UK who have one palm, since these trees have got into the mainstream of gardening over the past few years. The hard core enthusiasts who have got quite a few palms in their garden are about 1,000”.

The most northerly European palms are definitely in Scandinavia. The coast of Western Norway benefits from especially propitious growing conditions. But these days it seems that all over Europe people will buy anything from seedlings to expensive mature palms. In Germany gardeners cross their fingers a bit more. Climate change could soon make the increasingly common sight of garden palms, now encased for their protection in the coldest days of winter, an exotic feature of the neighbouring Northern landscape.

(30 April 2009)