In Northern Europe Christmas occurred during the middle of winter, when ghosts and demons could be heard howling in the winter winds. Boughs of holly, believed to have magical powers since they remained green through the harsh winter, were often placed over the doors of homes to drive evil away. Greenery was also brought indoors to freshen the air and brighten the mood during the long, dreary winter.Legend also has it that holly sprang from the footsteps of Christ as he walked the earth. The pointed leaves were said to represent the crown of thorns Christ wore while on the cross and the red berries symbolized the blood he shed.(text from: http://www.allthingschristmas.com/traditions.html)