While many of us have been complaining about the cold and snow this winter, some UK fruit growers are happy with the lower temperatures and the length of time that they have been around.

Winter chill, prolonged periods when the temperature stays above freezing but below 7oC, is essential for the successful growing and harvesting of many perennial woody crops, particularly fruits such as apples, pears, blackcurrants and hops.

And recent warmer winters in many areas where fruits are grown, including the UK, have taken their toll. Milder and shorter winters may now be seen as the norm. Declining winter chill is expected to be a growing problem as temperatures continue to rise as a result of climate change.

Now, in a bid to help commercial growers across the world, plant specialists at East Malling Research acknowledge the need to seek a more detailed understanding of the science behind the winter chill effect that triggers consistent time of blossoming, and subsequent fruit development which maximises the yield potential the following summer.

Head of Science at East Malling Research, Chris Atkinson, said: “We must not fall into a false sense of security after this winter. We need to be investing in approaches that enable UK growers to adapt to the changes already apparent in winter chill as well as the further decreases forecast to occur by the end of the century.

“Our climate records, kept since 1913, when compared to data from other UK locations, show that throughout the country the amount of winter chill has already declined. In the south-east we are already experiencing a 12 per cent reduction in the number of chill hours each winter, while the number of spring frosts has declined by a much higher percentage.

“Climate scenarios of the future suggest that as concentrations of greenhouse gases continue to rise, and global temperatures increase, the amount of chill the UK receives will decline further. Under the worst-case greenhouse gas emissions scenarios, winter chill in Kent has been predicted to decline by more than 50 per cent by 2080. Winters will continue generally to become shorter and milder. This winter has been closer to our experiences of 25 years ago.

“This will impact significantly on growers. As the south-east’s climate fails to deliver the period of chill and dormancy required for maximising the yield of commercial perennial crops, the traditional varieties that require larger amounts of chill will likely be disappearing or migrating north to chillier or longer winters.

“UK fruit production can ill afford any reduction in production efficiency given the economic situation and the demands for high production efficiency per unit of available land.

“Forward-looking growers will need advice on how to adapt to these new demands in order to sustain UK-based food production levels. This may require the use of alternative cultivars with lower chill requirements.

“There may also be a need to use entirely novel replacement crops which have low chill requirements. UK grape production is increasing and this crop generally has a much lower chilling requirement than traditional tree fruits, particularly apples.

“We also need to consider that similar declines in winter chilling are likely to become apparent in other fruit producing areas around the world including those that are key to the UK reliance on imports of perennial fruit out of the UK season; we need to step up our R&D in this area to sustain overseas growers as well.

“We need more research into measuring and modelling chilling responses in perennial plants. We are unfortunately unable to advise growers regarding the chill requirements of newly available fruit cultivars.

“With a greater fundamental understanding of how plants actually measure and respond to chilling we should be able to help growers overcome some of the negative consequences of warmer winters. For example, this could include breeding programmes to develop cultivars that can thrive with less chilling and produce the high quality plants and fruits with the long-term storage capacity we need to supply UK consumers. “