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When is the winter solstice 2018 and what does it mean?

For many, winter is a time for celebration and togetherness. A time for family and friendship amidst the frosts, snow and chilly, bare landscapes. It also heralds the longest night of the year - the winter solstice. But what is the solstice, what causes it and how does this affect our native wildlife?

When and what is the winter solstice 2018?

The winter solstice is on 21 December. This is the shortest day of the year in the Northern Hemisphere, when the North Pole is tilted at its furthest point from the sun.

In the astronomical calendar, it marks the start of winter which lasts all the way through to the spring equinox on 20 March. These start and end dates vary slightly each year due to the elliptical orbit of the earth around the sun. For example, the winter solstice in 2019 falls on Sunday 22 December.

The sun only rises for a few hours on the shortest day of the year (Photo: John G Cutler/WTML)
The sun only rises for a few hours on the shortest day of the year (Photo: John G Cutler/WTML)

According to the meteorological calendar though, winter starts on 1 December and ends on 28 February. Each of the four seasons is neatly assigned three months, and the seasons start on the same date each year.

Unsurprisingly, our coldest weather is usually in January and February, the middle of the season. There is a lag between the shortest day and the coldest days as the earth gradually cools. 2018 was an exception, with the Beast from the East bringing us a bitterly cold March.

How does winter affect nature?

The change in season affects all plant and animal life. Many life-forms are adapted to our changing seasons and have evolved to cope in various ways. 

Trees and plants

Deciduous trees and some plants shed their leaves due to low light and use this opportunity to deposit waste products in their leaves before they are dropped. Others ease away for the winter, often retreating below the ground altogether. 

Deciduous trees lose their leaves in winter (Photo: Ben Lee/WTML)
Deciduous trees lose their leaves in winter (Photo: Ben Lee/WTML)

Some annual plants will have set their seed and expired while others will just be coming into leaf and flower, such as henbit deadnettle or pansies. 

Some plants are evergreen and don’t lose their leaves, such as holly. This species has become a symbol of winter as its glossy leaves and bright red berries are a popular winter decoration in the home. Mistletoe is another evergreen which has been used to brighten up winter since the 16th century, despite all parts of the plant being poisonous. The tradition of kissing under the mistletoe is thought to date back to 18th century Druids.

Holly is evergreen so keeps its leaves through winter (Photo: Shaun Nixon/WTML)
Holly is evergreen so keeps its leaves through winter (Photo: Shaun Nixon/WTML)

Many plants actually depend on a cold period of some length and intensity before they will grow. The reduced temperatures are a trigger for their growth mechanisms. The early spring bulbs are classic examples, such as snowdrops, crocuses, daffodils and - best of all from my point of view - wild garlic. 

In fact, some plants won’t grow at all if winter temperatures aren’t low enough – it’s very difficult to get winter aconite to flourish in London, simply because it’s too warm in winter.

Nonetheless, there will always be a few plants in flower through the depths of winter because they are:

  • normally in flower at that time
  • growing in a heat island like London, or
  • reflecting the borderline effects of climate change.

Some plants and insects are now on show through all twelve months, including the white dead-nettle, Lamium album. Our largest native bumblebee, the buff-tailed bumblebee, Bombus terrestris, now flies all year – I saw one last January!

The buff-tailed bumblebee can be seen all year round (Photo: WTML)
The buff-tailed bumblebee can be seen all year round (Photo: WTML)

Wildlife

Icy temperatures make winter survival tough for some wildlife. Maintaining their body temperature and looking for food in plummeting temperatures can burn energy quicker than they can consume it. Different species deal with this by:

  • hibernating, which helps animals like dormice and hedgehogs to survive for long periods without eating.
  • going into a state of ‘torpor’, which reduces body temperature and metabolic rate for shorter periods. Badgers go through cycles of torpor which last for around 29 hours. 
  • reducing their activity. Red squirrels spend much more time in their dreys in winter, but still venture out for food when their supplies get low.
  • Swallows have long gone by now, but fieldfares, redwings and other migratory birds are already arriving in the UK from further north.
Badgers spend more time in their setts during the cold of winter, but will still come above ground to find food (Photo: WTML)
Badgers spend more time in their setts during the cold of winter, but will still come above ground to find food (Photo: WTML)

Help us track the start of winter

The Nature’s Calendar project tracks the effects of weather and climate change on wildlife across the UK – its records date all the way back to 1736! Telling us what you see helps us to track how the seasons are really changing, rather than relying on a calendar date.

Keep a look out for seasonal signs where you live, such as bare trees or snowdrops flowering, and record the dates on the Nature’s Calendar website.

In 2015, our amazing recorders spotted snowdrops flowering at the beginning of December!

By taking just a few minutes to share what you see, you'll be adding to hundreds of years' worth of important data for studies worldwide. Every record is crucial. We couldn't do this work without you!

Your wildlife observations are vital to Nature's Calendar

Tell us what you've seen