Unseasonal wild flowers in Cardiff: Winter 2012
New Years Day 2012 witnessed unusual widespread flowering of plants around the city of Cardiff.
The very mild winter weather of 2011-2012 ended the second warmest year on record since 1910. The mild weather allowed many wild flowers to continue flowering through the winter, when they would normally have finished in the autumn.
On New Year's Day 2012, a wild flower hunt by Dr Tim Rich (Amgueddfa Cymru) and Dr Sarah Whild (Manchester Metropolitan University) showed how unusual the 2011-2012 winter had been: a search around Cardiff found 63 wild flowers in flower. Most of the wild flowers had continued to flower because autumn frosts had not been severe enough to knock the plants back for the winter, but three spring-flowering species - hazel, primrose and lesser celandine - were flowering very early. The 63 wild flowers found is way above what would normally be expected, which is perhaps 10-20 species.
Not only is the overall diversity of species flowering unusual, but so was the repeated pattern of widespread flowering of many individual plants of each species. Good numbers of Hogweed, Knapweed, Red Clover and Meadow Buttercup were found in different sites. Cock's-foot grass with flowering heads were also seen for about 1.5 km along the central reservation on the A470 road.
Especially interesting was the Mediterranean grass Compact Brome which was in full flower. Compact Brome is a winter annual known to be sensitive to cold, which only persists in south-western Britain. It would normally flower from May to July in Britain, but the winter flowering is more indicative of its behaviour in the Mediterranean, where it has to flower early in the year to avoid summer drought.
2011 - 2012: Winters of contrasts
The 2011-2012 winter was a complete contrast to that of 2010-2011, when there was the coldest December on record. The only plant seen flowering on New Year's Day 2011 was Gorse - and this was not so much flowering as frozen under a blanket of snow.
The mild winter also allowed many garden flowers to bloom early, with Camellia, Forsythia and Laurastinus flowering in January. The findings of the survey received national media attention, and the response to the coverage made it clear that similar observations were being made throughout Britain.
If the unusual flowering patterns are a result of global warming, they may indicate what we will see in the future. Although the wild flowers were flowering, they could not set seed as their pollinators such as bees and moths were not flying. Cold winter weather normally knocks back pests such as aphids and pathogens but, if they survive during mild winters, these could now be a more significant problem. Arctic-alpine plants are known to rot off in warm, wet winters, so could be disproportionately affected. Warmth-loving and evergreen species could flourish.
Article by: Tim Rich: Head of Vascular Plants
Article Date: 20 December 2012