At this time of year, you hear an awful lot of jokes about kissing under the mistletoe. For years, the creeping - not creepy - plant has been part of our Christmas decor, even though it has nothing to do with the birth of Christ. So what exactly is it? And where have the myths around mistletoe - wow, trying saying 'myths around mistletoe' fast - come from? Mistletoe is a parasite that grows in various forms on trees across Europe, Africa, Australia and North America. Unlike many other plants, mistletoe remains alive and green during winter, so it's easy to spot on apple or oak trees. The plant has leathery, oval leaves and red or white berries. These berries are eaten by birds who then spread their seeds from one branch to the next. This means that, again unlike other plants, mistletoe never has to touch the ground. In fact, people once thought mistletoe grew from bird poop. Therefore it's ironic that in South Africa the berries are used to make a sort of glue to trap birds. However, although mistletoe can be dangerous if used by people who don't know what they're doing, it has earned its nickname of 'All-heal' for a reason. Over the years, the plant has been used to cure many things by many people - most famously by the druids, priests of an ancient European religion. Five days after the first new moon following the winter solstice - the name for the shortest day of the year - the druids would gather mistletoe. Working by moonlight, they took only the plants growing on oak trees, which they believed to be sacred. The mistletoe was placed in a special white cloth to keep it clean and untouched by the ground. After special ceremonies in which two white bulls would be sacrificed, sprigs of mistletoe were handed out to everyone. These were hung over doorways, as people believed the plant had strong magical powers and could ward off disease and witchcraft. Whether it can help against swine flu, though, hasn't been proven. There are lots of legends about mistletoe, most of them European, of course. Some French folk believe the plant is poisonous because it grew on the tree used to crucify Christ and is therefore cursed. The Norwegians believe the white berries are the tears of Frigg, the goddess of beauty, love and marriage. Frigg wanted to protect her son, Balder, so she asked everything that grew not to harm her precious boy. Loki - all-round bad god and now super-villain in Marvel comics - worked out that mistletoe didn't count because it doesn't touch the earth. Loki used it to poison Balder, thereby earning his infamous reputation. Mother Frigg wept so hard she turned the mistletoe berries white with her tears - and hey presto, her son was cured. Frigg was so happy she forgave the plant and kissed anyone who walked under it. These days, mistletoe is an excuse to steal a kiss from your true love, or at least someone you fancy. If you catch them standing under it, they're fair game. If you want to play by the book - but these days few people do - the boy should kiss the girl and, after each smooch, take one of the white berries. Once all the berries are gone, the kissing has to stop. But, whether you follow the rules or not, now's the time to pucker up and enjoy.