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According to popular belief, plants hibernate during the winter and restore their functions in the spring. Martin Küttim, a junior researcher at Tallinn University explains how this is actually untrue, as many evergreen and wintergreen plants grow and photosynthesise during the winter.

Snow is a great thermal insulator, and even during harsh weather, the temperature under the snow can still be above zero C. The environment under the snow is very moist, which means there is no danger of dehydration for plants. Unless the snow is unusually thick, there is also enough light for photosynthesis.

Many evergreen plants are able to keep photosynthesising during the winter and thus elongate their vegetation period. According to researchers from Helsinki University, the photosynthetic activity of the lingonberry during the winter under a couple dozen centimetres of snow is about a third of summertime photosynthesis, when the temperature has risen from minus ten to plus 15 degrees C – this is a remarkable result when considering the whole year.

We know even more about crops: winter wheat (Tricitum aestivum) can even increase its growth rates during a colder period in the winter. An even more extreme example is the common mallow (Malva neglecta), which increases in photosynthesis rates twofold in the winter.

The king of swamps, peat moss, also grows rapidly in the winter, helping tie down carbon from the atmosphere. According to research conducted by the Tallinn University Institute of Ecology and Helsinki University, we know that a third of the annual growth of peat moss happens during the winter. Given that a third of all carbon on land masses is trapped in peat, and it comes mainly from the decay of peat moss, this winter growth is remarkable in the context of carbon circulation.

Actually, the role of winter is important in the life cycles of all plants: the winter determines how well plants do in the summer. Constant thawing and freezing cycles during a winter with little snow damage plant tissue and diminishes their ability to grow and multiply, which in turn threatens to kill significant parts of plant population.

Unfortunately, the changes in climate on our latitude are the most rapid in wintertime – the period of snow cover is ever shorter, which leaves plants unprotected from changes in the temperature. As the plants’ ability to cope with winter stress vary, such winter climate and its changes will determine our flora in the future.