Wild Poinsettia is an erect annual, growing on a sturdy stem to 40 inches high, unbranched below the inflorescence. The stem is smooth and green.
Leaves: The long, stalked leaves are alternate, variable in shape ranging from very linear to oblong with lobes and a few teeth. A few leaves near the inflorescence may be opposite with short stalks. The upper side is a medium green, the underside paler with fine whitish hair and sparse longer hair on the veins.
The inflorescence is a small terminal cluster at the top of the stem or top of each stem if the inflorescence branches.
The flowers are of a type that is unique to the Euphorbia genus. The flower parts are grouped together in a structure called a cyathium. Inside at its base are nectar glands and these have outward flaring appendages that look like petals. The underside of all this looks like a cup, about 1/8 inch across. From this base around the nectar glands appear the male flowers which have one stamen each with a pair of yellow anthers. Arising from the center of the cyathium is the stalk of the female flower, which has a green 3-lobed ovary with 3 divided styles emerging. This eventually produces 3 oval brown seeds. Surrounding the flower cluster are leafy bracts that turn reddish at their base end, providing a splash of color for which the plant is known.
Seed: The mature flower produces 3 oval (almost round) black seeds, from which the plant self-seeds. They have neither wings nor pappus.
Toxic: See notes at bottom of page.
Habitat: Wild Poinsettia needs adequate moisture and can grow in shade to partial shade but will do best in sun. In the wild it inhabits open woods, floodplains, disturbed areas. Seeds are difficult to start. Some germinate without cold stratification, others seem to require 30 to 60 days of cold stratification. Plants will self seed but are subject to crowding out by larger more aggressive plants. An occasional plant may pop up in a different place if a seed has been transported.
Names: The genus name, Euphorbia, is said to refer to Euphorbus, the Greek physician of King Juba II of Numidia. Euphorbus found medicinal uses of certain plants of this genus. Carl Linnaeus named the genus after him. The species name, cyathophora, is from two Greek words for 'cup-bearer' and refer to the cup-shaped base of the flower containing the glands. The author name for the plant classification from 1786, ‘Murray’ refers to Johan Andreas Murray (1740-1791), Swedish physician and botanist who investigated and published on plant derived medicines. His most important work was the 6 volume Apparatus medicaminum. At some time in the past the name Poinsettia cyathophora was used but that is not accepted today.
Comparisons: There are a number of similarities of this plant to E. heterophylla which goes by many of the same common names. Some references state that E. heterophylla is the species that has the variable leaf shape; Flora of North America (Ref. #W7 Vol.12) agrees that it does but also states that E. cyathophora has this polymorphic leaf shape, but not to as great an extent. The plants that were historically present in the Garden seem to have had a variable leaf shape as the historical photos below show. The Minnesota DNR and the University do not list E. heterophylla as present in the state although Eloise Butler used that species name - see below.
Above: These two photos represent the variation in leaf shape reported for Euphorbia cyathophora and E. heterophylla. The flower structure is more clear in the 1st photo where the 3-lobed green ovary with its branched style on top rises above the cup-like cyathium and the anthers of the male stamens. 2nd photo is a historical photo from a Kodachrome by Martha Crone in the Garden, July 29, 1950.
Below: A leaf of E. cyathophora - 1st photo - the upper surface is a medium green with just the suggestion of teeth on the margin; 2nd photo - the underside is paler color due to very fine hair with sparse longer hair on the veins.
Below: The flower structure of the cyathium: Rising from the center of each cyathium is the stalked green female 3-lobed ovary with 3 divided styles emerging. Around the base of the ovary stalk are the nectar glands from which rise 3 male flowers per cyathium, each with two yellow anthers.
Below: Historical photo of Wild Poinsettia in the Garden taken on Sept. 5, 1952 from a Kodachrome by Garden Curator Martha Crone.
Notes: Wild Poinsettia is not native to Minnesota but introduced long ago. Eloise Butler planted Wild Poinsettia in the Garden on July 29, 1913 and noted blooming plants on Aug. 3, 1914. Eloise obtained the plants from the area of Ft. Snelling (Minneapolis). In 1918 more from two places around Minneapolis. She used the species name E. heterophylla although the U of M Herbarium lists no collection of that species in the State. Martha Crone rescued a few plants from a New Ulm MN building site in the late 1940s when they were about to be destroyed. Martha's husband Bill was from the New Ulm/Mankato area and they would find out such information on their visits there. This name was still in us when Martha Crone prepared her 1951 Garden census. On the 1986 census however, the name changed to E. cyathophora.
Wild Poinsettia is found in the U.S. in all the southern states northward as far as New Jersey; in the central states north to Ohio, Wisconsin, Minnesota, South Dakota; and in the far west it is found in the states bordering Mexico. It is native to Mexico and is spread to many countries, as has it's cousin, the Christmas Poinsettia, E. pulcherimma. Within Minnesota it has been found in the wild in 19 counties, mostly in southwest part of the state and along the Mississippi River from the Iowa border to the metro. Some authorities consider it to be native, but others such as the Minnesota DNR consider it as introduced. The Euphorbias are a large world-wide genus. There are 14 members of the genus with known populations in Minnesota and several others were once reported but there are no collected specimens.
Toxicity: The milky latex juice of a number of Euphorbias has toxic effects on humans and animals. Foraging on the plant has been known to be deadly to animals. There is concern that the toxin is carcinogenic to humans. There is not a great deal of information about the toxicity of this particular species other than the toxic properties of the acrid latex is probably due to a resin not to an alkaloid or a glucoside. However, Kinghorn, in his book, Toxic Plants (Ref. #15), devotes an entire chapter to the carcinogenic and irritant properties of the Euphorbiaceae.
References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applied. Distribution principally from W1, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.
Identification booklet for most of the flowering forbs and small flowering shrubs of the Eloise Butler Wildflower Garden. Details Here.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"