Hannah Stephenson discovers some myths and truths about our most popular Christmas plant.

It's the top-selling plant every Christmas - a staggering eight million will be sold in the UK this year alone.

But how much do you know about the poinsettia, apart from the fact that it's generally red and if you put it in the wrong place, it loses its leaves?

Here are some facts you might not know about our favourite festive plant, with help from Squire's Garden Centres (squiresgardencentres.co.uk), which sells 15,000 poinsettias a year.

1. It can grow to over 3.6m tall

Of course, it won't reach that sort of size in a small pot, but in its native habitat in tropical climates, it can grow to nearly four metres, with leaves measuring up to 20cm across. In fact, it's classed as a small tropical tree - Euphorbia pulcherrima - belonging to the euphorbia plant genus.

2. Leaves can dye fabric

In the 14th and 15th centuries, poinsettia leaves were used by the Aztecs to dye fabric for clothing, while the sap was used for medicinal purposes and was said to help control fevers. Red was also considered a symbol of purity, so the plants were often used as part of religious ceremonies.

3. It used to be considered a weed

The poinsettia is a native of Mexico, where it is called La Flor de Nochebuena, which translates to Flower of the Holy Night, referring to Christmas Eve. It was named after Dr Joel Roberts Poinsett, an amateur botanist and the first American ambassador to Mexico, who introduced the plant to the US.

He discovered the brightly-coloured shrub growing by the side of the road in southern Mexico in 1828 and sent cuttings back to his plantation in South Carolina, although initially, they were dismissed as weeds by his peers.

4. TV helped start the trend

Poinsettias didn't become traditional holiday decorations until the entrepreneurial Ecke family started promoting them more than century later. Paul Ecke Jr sent free poinsettia plants to TV studios across the country, including The Tonight Show and Bob Hope's Christmas Specials.

5. It's not as poisonous as you think

While some have described the plant as 'deadly', this myth was started in 1919 when an army officer stationed in Hawaii found his two-year-old child dead underneath a poinsettia and thought the child had eaten a leaf from the plant.

Researchers at Ohio State University, however, have found that a child weighing 50lb would have to consume more than 500 poinsettia leaves to incur any ill effect.

They are also only mildly toxic to cats and dogs. Even a small dog would have to consume a huge amount of the poinsettia to have a serious reaction.

It is highly unlikely an animal would eat more than one bite, because the leaves taste so bitter. However, if you have pets, it's worth keeping them away from the leaves, just in case.

And, like all euphorbias, the poinsettia has a milky sap which can produce skin problems if not washed off immediately.