How did poinsettias become our favourite Christmas plant? Gardeners have probably heard that a reducing day length triggers flowering and the development of those glorious red bracts. But do you know how this wild plant was ‘trained’ to be an inside plant, and not drop all its leaves?
In the 1970s Robert N. Stewart, a geneticist with the USDA’s Agricultural Research Service (ARS) looked closely at the poinsettias that were being used to bring a festive red and green display to hotel lobbies around Christmas time. He noticed that he could go into a meeting at the hotel and then find that by the time the meeting finished, the poinsettias had reacted so quickly to being in artificial indoor light that they had already begun to drop their bracts and leaves.
Stewart began breeding poinsettia that were naturally much more compact than the 3m (8ft) tall wild Mexican plant, and that would also hold their leaves outside the ideal conditions of a greenhouse. The ‘Ruff and Ready’ poinsettia varieties he created are still used as parent material for the many colour variations we enjoy to day.
Newer work by ARS plant pathologist Ing-Ming Lee has concentrated on finding why these compact poinsettia forms are so dense and naturally free-branching. It seems that plant phytoplasmas, which can also cause plant diseases, cause this prized habit.
Each year Americans buy 80 million poinsettia over the 6 week holiday period, making it the USA’s favourite potted plant.
[Note – for all those in the southern hemisphere enjoying poinsettias on the Christmas table, the plants have been induced to flower in summer by using black-out curtains in the greenhouse to mimic a reducing day length. But it means that they will never flower at Christmas again, unless you remember to put them to bed early every night!]