In Scandinavia, a period of festivities known as Yule contributed
another impetus to celebration, as opposed to spirituality. As Winter
ended the growing season, the opportunity of enjoying the Summer's
bounty encouraged much feasting and merriment.
The Celtic culture of the British Isles revered all green plants, but
particularly mistletoe and holly. These were important symbols of
fertility and were used for decorating their homes and altars.
New Christmas customs appeared in the Middle Ages. The most prominent
contribution was the carol, which by the 14th century had become
associated with the religious observance of the birth of Christ.