Published December 4, 2021, in the McAllen Monitor
Story and photos by Anita Westervelt, Texas Master Naturalist
The beautiful crimson bracts of the poinsettia plant have long been associated with Christmas. Its botanical name is Euphorbia pulcherrima, meaning the most beautiful Euphorbia.
While not as vibrant nor commercially lucrative, the Rio Grande Valley has its own beautiful euphorbias: wild poinsettia (Euphorbia cyathophora), also called painted leaf, dwarf poinsettia and fire-on-the-mountain, is a North American annual. It grows to 18 to 24 inches tall, taller if growing in shade and reaching for more light.
A close cousin is the painted spurge (Euphorbia heterophylla), also called summer poinsettia, Mexican fireplant and painted euphorbia. Native to tropical and sub-tropical America, it is found in the southern half of North America through Mexico to South America. It has been introduced to many countries, including Africa, Asia, Europe and Australia.
The commercialized poinsettia (E. pulcherrima) is native to Central America; it has been cultivated for more than 150 years and sold worldwide. There are more than 100 varieties in colors ranging from red, white, pink, salmon, burgundy, yellow, purple, marbled and speckled. In its native habitat, it is a perennial shrub that can grow 10 to 15 feet tall.
The large Euphorbiaceae or spurge family of plants consists of about 7,500 species and 300 genera. The euphorbia genus has about 1,600 species. Unique characteristics set these plants apart from other botanical families. Most of the species have a toxic white latex in their stems and leaves that is an irritant to skin, eyes and mouth. Many herbivores avoid these plants because the sap can irritate the lining of their mouths and digestive tracts.
Euphorbia flowers are unique in that they rarely have petals. In fact, the flowers are tiny and massed together in a cluster called a cyathium -- a cup-like cluster of modified leaves enclosing a female flower and several male flowers to resemble a single flower. This feature is present in every species of the genus Euphorbia, but nowhere else in the plant kingdom.
Instead of the flowers being the eye-catcher, they tend to be surrounded by colorful bracts, which are leaf-like structures just below the flower clusters. Leaf bracts are a modified or specialized leaf, often different in size, shape, color or texture to the foliage leaves. Bracts function differently from leaves. Leaves may be anywhere along the stem; bracts are generally located on a stem just below a flower, a flower stalk or an inflorescence -- the plant’s floral axis.
Both Valley native species attract bees, butterflies, flies, wasps and ants.
In the wild, in regions of Central America and Mexico, hummingbirds feed on the sugar-rich nectar of the yellow flowers of E. pulcherrima, significantly aiding in the plant’s pollination.
December 12 has been designated as Poinsettia Day. The date marks the death of Joel Roberts Poinsett (1779-1851), a physician, botanist and the first United States Ambassador to Mexico, who first introduced the poinsettia to the United States from Mexico in 1828, by sending cuttings of the plant to his home in Charleston, South Carolina.
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