I came across this plant on Matecumbe Key in Florida a couple of months ago. I hadn’t got around to identifying it, but while thumbing through a field guide the other day I accidentally stumbled across it. It seems most commonly known as fire on the mountain (Euphorbia cyathophora, Euphorbiaceae), but has a host of other common names including wild poinsettia, dwarf poinsettia, false poinsettia, Mexican poinsettia, Mexican fire plant, and painted-leaf spurge.
This plant has leaves that are extremely variable in size and shape. They can appear thin and grass-like as with this specimen, broad and fiddle-shaped, or anything in between. The red blazes are on the surfaces of young, bract-like leaves; they’re not part of the flowers. The flowers themselves are the inconspicuous green structures in the center.
Native to the southeastern United States southward to northern South America, fire on the mountain has been introduced in many new areas as an ornamental. It spreads readily, however, and has since become invasive throughout the Pacific and southeast Asia.