Can holly forecast winter weather?

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  • Holly struggles to grow in the snow, especially in spring when it should be flowering. Source: Joe Giddens/PA.

    Robins are often associated with holly as the eat the berries. Source: David Jones/PA Wire.

    Avoid your berries being eaten by making sure there are plenty of seeds available for the birds (and squirrels) to eat. Source: Anna Gowthorpe/PA Wire.

  • Can holly forecast winter weather?
    10.12.2011 15:51

     

    Nearly everyone has heard the old wife’s tale; lots of holly berries means a big freeze is on the way. However, is this actually true? With masses of red berries on the holly bushes this year, are we set for another cold winter? Based on the last five years it could be argued that it is true, however there are other factors that affect a bumper crop of berries.

    Holly is one of the best known evergreens because of its association with Christmas. There are over 500 different species of holly or Ilex. Hollies are dioecious, meaning there are both female and male plants, which cannot bear fruits without the other growing close by. The most common species in the UK is Ilex aquifolium, with the female plant growing the berries. The berries are poisonous to humans however they are one of the few berries available in the winter and therefore are loved by birds. This is may be one of the reasons why Christmas cards often illustrate robins and holly together.

    According to gardeners, the holly this winter is the best for over 70 years, but there were also plenty of berries in 2008 and 2010. To support the tale, 2008 and 2010 were both followed by chilly winters, however so did 2009 when berries were scarce. It is the spring months that actually affect this quantity of berries, not the likelihood of a chilly winter. If, in general March and April are cold, but not freezing, and a warm summer follows then holly with be fruitful. This is because harsh frosts kill the white flowers produced in early spring, so pollination does not occur. Similarly, if the holly is not regularly watered in summer, it is to hot or the plants are not in the shade, no berries will grow as the flowers fall off early. For this reason there are surplus berries on holly bushes this year. The UK had a chilly January, followed by the warmest spring in over 300 years, with temperatures in the south-east 2.5C above average. However the summer was reasonably moist in most areas and cool, especially in June, which allowed flowers to bloom. In addition to this, a warm autumn has meant there are also surplus seeds available for birds to eat, so they are not eating the berries as early.

    According to the Woodland Trust, holly is fruiting about 17 days earlier than a decade ago, with an annual trend of berries increasing. It is thought this is due to the climate becoming warmer. If the current warming continues then this trend of plants flowering and fruiting early will continue, as for every 1C increase in temperature, the growing season for plants will increase by 10-20 days. So based on these findings, there will be more of the bright red berries on the holly in the future, but this will not necessarily imply a cold winter.

    By: Sally-Jean Webb