‘Tis the season for Flora and Fauna Friday because I have our native relatives of the crimson tropical trimming on display this holiday. This week we’re talking about Mexican Fireplant (Euphorbia heterophylla) and Fire-on-the-mountain (Euphorbia cyathophora), both who go by the name Wild Poinsettia.
Mexican Fireplant is a low-growing annual plant with large alternate leaves of variable shape. It’s in the same genus as the tropical ornamental Poinsettia (Euphorbia pulcherrima). It blooms in late summer producing a cluster of small, inconspicuous flowers above a ring of bracts, flecked with spots of red and a tinge of pink. Fire-on-the-mountain has more impressive crimson coloration to the bases of its bracts. It’s life history is much the same as Mexican Fireplant but with a greater tolerance for shade.
What’s interesting about the flowers of Poinsettias is that there are multiple layers of imitation going on. The red leaves of Poinsettias are bright, colorful, and draw in pollinators like petals but they’re not petals. They’re regular leaves modified to be colorful. So where are the petals? If you look closely at the central cluster, you’ll notice several pale yellow structures that look a lot like petaled flowers. However, the color you see is not the flowers themselves. Rather, they’re parts of a complex compound flower unique to the Euphorbiaceae family called a cyathium. The actual flowers are unisexual and lack both petals and nectar! The pale yellow structures that resemble petals are again modified leaves called bracteoles. Outside of these bracteoles you may notice a golden funnel shaped structure. That’s a nectar gland. Its sole function is to produce nectar for pollinators. The flowers themselves are located in two places. The tiny white stalks with two pink discs on the end are the male flowers. The three-sided lumpy ball hanging out of the middle of the male flowers is the maturing seed capsule and that small cone on the other side is the female flower. The cyathium is truly odd and unlike the flower of any other plant family. The next time you see a Poinsettia, appreciate the weirdness that makes it as beautiful as it is!
