Ivy
The druids believed that ivy had magical properties that would repel the devil.  It was consequently often displayed as a means of preventing harm. 
   According to legend, if ivy grew on the walls of a house, the occupants would be protected from witches and other evil spirits.  If it did not grow however, disaster was imminent.  It was also believed that if the plant died, the house would pass into other hands, most likely from infertility.