The wild poinsettias grow around 15 feet tall and are a single stemmed shrub with smaller bracts being about an inch wide and four inches long. Commercial poinsettias have bracts that are three to four inches wide and four to six inches long.
“The domestication process has created a plant that is a lot more showy and compact and able to be produced commercially in large numbers in containers,” said James Faust, floriculturist and associate professor at Clemson University. “It’s really a totally different plant, except for the flower, you wouldn’t recognize it.”
The plant was introduced to the United States when the first American ambassador to Mexico, Joel Roberts Poinsett, sent the plant home to his greenhouses in Greenville, South Carolina.
“Poinsett was a horticulturist and was really interested in how plants might be used to help the economy develop, so he kind of facilitated the shipment of plants between Mexico and the United States that had potential commercial value. So, he’s sending food crops that he’s seeing in Mexico, things like avocados, and he’s sending seeds up from Mexico while he’s the first ambassador,” Faust said.
Yet the plant that Poinsett introduced to the United States, Faust suspects, was not wild. It had already been domesticated by the Aztecs, who selected plants from the wild and grew them in their landscapes. The Aztecs were in fact the first to have botanical gardens and domesticated other flower crops like marigolds, zinnias and dahlias.
“We don’t have direct evidence that they domesticated the poinsettia, but they were certainly used in the landscape and had already been collected out of the wild when the Europeans had first arrived,” he said.
The Aztecs’ botanical gardens cultivated plants for medicinal purposes, and the people used the poinsettia as a source of purple dye and as medicine for fevers.
“My suspicion is that when you look at the drawings of the first plants Poinsett brought back, they don’t look like the wild ones,” Faust said. “They look more like a domesticated poinsettia and that the bracts were much larger, but that’s why I think the plants were already domesticated to some extent. Now it’s still not anything close to a commercial poinsettia today, but it was certainly a lot showier than the wild ones.”
It has only been over the past 100 years that the commercial industry has really domesticated the poinsettia, bred varieties for their compactness and larger flowers, allowing it to become a commercial product that can be grown in a small pot and produced in the millions.
The wild poinsettias are only scattered along the western coast of Mexico and tucked away in deep canyons and ravines, so a person really has to go out of the way to find the ancestors of the Christmas flower.
While they are not on the endangered species list, there is concern about genetic purity for the wild poinsettias.
“If you have modern varieties near some these wild populations, if the insects pollinate the wild ones with pollen from commercial varieties, you’re going to lose the genetic purity of them,” Faust said. “So that’s a bit of a concern, and preserving those wild spaces that they still grow in because it’s really the only place they survive well in the wild when they’re pretty isolated. A lot of those are still not national forest type of lands.”