Every household is invaded with poinsettias (euphorbia punchemingobbia) at this time of year; they're an indispensable present for someone who's already got a shedload of socks, eighteen bad taste jumpers and cellars full of bath salts.
And every household is similarly invaded with Auntie Gertie who will tell you that they're poisonous and that you should be moving next door if one of these arrives (which would be OK but next door have got them too).
The idea originated in Glossop in 1934, when a small child munched its way through the family poinsettia and was then run over by a bus. There WERE queries as to whether this was poisoning, but the story was repeated at the bus stop, Diana's Diner and the Cats' Protection shop - and passed into urban mythology. There was some initial confusion with helleborus niger, and because 'Christmas Rose' was the name of the madame of the local knocking shop.
However, Professor Anna Prongg has been conducting a seventeen-year investigation into the toxicity of the poinsettia. It took so long because not that many people live on a staple diet of poinsettias, and had to be force fed. Only one case of serious poisoning was found during all that time, but closer scrutiny showed it was the result of overindulgence on brandy and mince pies.
"Mind you", she said. "These things taste so awful that you're more likely to get poisoned by the saveloys at Diana's Diner. I'd rather eat stuff off the bird table".