Flowering Spurge

Euphorbia corollata

Last week we looked at a milkweed, which had very odd flowers.  This week we look at a plant with flowers that are odder still.  At first glance, see the closeup at bottom right, they appear rather ordinary, if small, with 5 brilliant white petals surrounding a cluster of sexual parts that seem odd only in being too abundant.  Botanists, however, say that the flowers of all members of the genus Euphorbia are very tiny and much simplified.  In fact, within the five white "petals" in the center of the picture at bottom are probably over a dozen flowers.  The male flowers are reduced to a single stamen, and the female flowers are usually reduced to a single pistil.  None of the flowers have petals or sepals.  One female flower will be surrounded by several male flowers in a tiny cup called a cyathium.  In flowering spurge several cyathia are clustered together and surrounded by nectar-producing glands.  These glands have white appendages which look like petals, and are called petal-like appendages by botanists.  If it weren't for the petal-like appendages, flowering spurge would be scarcely noticeable, and, in fact, many members of the genus lack these appendages and are rarely noticed by ordinary folk.  In the picture at lower left, looking down on an inflorescence, one can see several female flowers that have begun to expand and grow into fruits, which are three-parted capsules.

Flowering spurge likes dry woods in the east, and loves dry prairies in the midwest, where it is very abundant.  It can be found from Massachusetts and southern Ontario to Minnesota, south to Florida and Texas.  In Wildwood it favors the bluffs under the powerline along Wildwood Drive.

The genus Euphorbia is an enormous one, with about 1000 species, almost worldwide in distribution, but occuring mostly in the tropics and in arid regions of the Old World.  All of them have the highly reduced flowers described above; many have colored or white petal-like appendages, but many do not.  All of them also have white milky sap that is more or less poisonous, acrid, and irritating.  I was told once of parks in the Caribbean where signs warn people not to sit under the trees, which are members of Euphorbia and produce sap so acrid and irritating that sitting under them can produce blisters from the tiny drops of sap that fall from them.

Flowering spurge is also called devil's milk, presumably on account of the poisonous sap.  It has been used medicinally to induce vomiting and bowel movements, and the common name "spurge" comes from the Old English word to "purge."  The sap of this plant has also been spread on the skin to remove warts. However, these uses have fallen out of favor with herbalists as the plant can cause violent poisoning if the dose is too large.

A familiar Euphorbia is the poinsettia, a Mexican species which has brilliant red leaves around the cluster of flowers, and is very popular at Christmastime.  In cultivation, forms with pink and white leaves have been developed.  Snow-on-the-mountain has beautifully white-marked leaves; it is a midwestern species sometimes grown for ornament.  Cypress spurge is an ornamental with yellow petal-like appendages popular as a cemetery planting.  Crown of thorns is a thorny woody species which has flowers similar to flowering spurge, except that the petal-like appendages are deep red (or bright yellow in a cultivated form).  Many desert species, especially from Africa, are thick, spiny and succulent, sometimes producing no leaves, and thus greatly resemble cacti.  This is considered a classic example of convergent evolution, where widely different, unrelated species in similar habitats evolve to look much alike because they have to solve the same problems to survive.  There are no native cacti in the Old World, and no native cactus-like spurges in the New World.  The many odd species of succulent spurges are popular with specialist plant collectors.  The Radford University greenhouses have a small but excellent collection.