Poinsettias Are For the Birds
by Jim Hole
No question, poinsettias are incredibly showy plants. The poinsettia’s Latin name Euphorbia pulcherrima alludes to its gorgeous display, pulcherrima means beautiful in Latin.
But the truth is that the flowers really aren’t all that spectacular. Instead, it’s the large colourful leaves called bracts that catch our eye and get us in the Christmas spirit. The poinsettia’s real flowers are the tiny, yellow structures located at the central hub of each cluster of bracts—nice, but I wouldn’t describe them as spectacular.
Still, beauty is in the eye of he beholder, and from a poinsettia’s perspective our judgment of its flowers is irrelevant. The only judges poinsettias really care about are birds—hummingbirds to be specific.
In the wild (i.e. the regions of Central America and Mexico) hummingbirds seek out poinsettias. These tiny birds feed on the sugar-rich nectar produced by the flowers and inadvertently spread poinsettia pollen when flitting from plant to plant. This dispersal of pollen transfers each individual plant’s genes far and wide, ensuring that there will be future generations of poinsettias (some insects do transfer pollen but they play a much smaller role).
However, before hummingbirds will deign to visit poinsettias, the plants must undertake a splashy advertising campaign. Since the flowers are small they don’t catch the bird’s eyes, so poinsettias have cleverly adapted and modified some of their upper leaves to display bright-red pigments.
This advertising strategy works because all birds have a keen sense of colour; not that far removed from our own. Also, since birds, including hummingbirds, don’t have much of a sense of smell, poinsettias don’t waste their time producing aromatic compounds. In fact, most bird-pollinated flowers have little fragrance for this vary reason.
But if poinsettias depend on their bright red bracts to attract hummingbirds, one might ask “why do white poinsettias exist then?” Even though a poinsettia’s normal bract colouration is red, occasionally, a plant will mutate and produce pigment-deficient bracts. Normally, this would spell doom, reproductively speaking, since hummingbirds tend to ignore white bracts. But whenever a poinsettia sprouts a mutation—white or otherwise—we humans find the beauty of these new types irresistible and begin propagating them.
So while hummingbirds might find white poinsettias uninspiring, there are a lot of people who love them—me included. White poinsettias don’t last too long in the wild but they do just fine with the help of amateur and professional plant breeders.
— Jim Hole