Autumn has come twice this year, according to the Woodland Trust, after the dry spring and invasive pests caused some trees to drop their leaves early.
Traditionally the season of “mists and mellow fruitfulness” falls in late September as trees begin to turn gold and shed foliage. But this year many species lost their leaves early due to one of the warmest and driest springs on record. The Royal Horticultural Society recorded leaves turning yellow on hazelnut, acer and laburnum at the beginning of August. Horse chestnuts, or conker trees, lost their leaves early due to the leaf miner moth, from Turkey, that has been spreading across the country. Autumnal flowers like winter hellebores, viburnum and magnolia also came out early. But this was a “false autumn” caused by a lack of water rather than cold weather, explained Professor Tim Sparks, nature adviser to the Woodland Trust. Trees shed their leaves during a drought in order to retain water and survive. He said the real autumn is only just happening as native species like oak and ash, that are more used to the capricious British weather, begin turning. Prof Sparks urged the public to help record the “real autumn” by looking out for the vivid red, golds and browns of turning leaves. "Autumn is the best season to get out and make the most of our trees and woods, the beautiful reds, browns and golds are an awe-inspiring sight. We're calling for the public to help us record the changing seasons, which helps inform scientists about the effects of climate change on our native flora and fauna." The study of the seasons, known as phenology, is important for measuring how the weather is changing in Britain with global warming.
The Woodland Trust recorded the earliest spring so far this century this year, leading to the expectation that autumn will come early because of the “shelf life” of leaves. However this is not necessarily the case, if temperatures remain high and there is enough rain trees may continue blooming later. It tends to be more difficult to work out when autumn falls because there are more complex factors than just temperature, such as rainfall and high winds. Ultimately the leaves will turn as the days get shorter, meaning plants and trees photosynthesise to a lesser extent and produce less chlorophyll – which provides the green colouring seen in leaves. Sudden drops in temperature at night also destroy the chlorophyll, all of which leads to the appearance of the yellows, reds and browns of the season. Data recorded by the charity over the past decade suggests that trees across the UK will on average be showing the first signs of autumn colour during late September, with so-called 'full tinting' appearing by late October. reds, golds and browns. The benchmark date for the UK's most symbolic tree – the oak – to show the first signs of autumn colour is September 25th2, with full tinting appearing by October 30th. The Woodland Trust has only been recording the onset of autumn for ten years so it is too early to find a trend due to climate change. The public are not only asked to look for the turning of leaves but the departure of summer migrants like swallows and the arrival of winter migrants like fieldfare. - Telegraph.