Poinsettia

The poinsettia was described as a new species in 1834 by German scientist Johann Friedrich Klotzsch.[5] Klotzsch credited Carl Ludwig Willdenow with the species name "pulcherrima", and the authority is given as Willd. ex Klotzsch. The holotype had been collected in Mexico during an 1803–1804 expedition by Alexander von Humboldt and Aimé Bonpland.[6]

It was known by the common name "poinsettia" as early as 1836,[7] derived from Joel Roberts Poinsett, a botanist and the first US Minister to Mexico.[8] Possibly as early as 1826, Poinsett began sending poinsettias from Mexico back to his greenhouses in South Carolina.[9] Prior to poinsettia, it was known as "Mexican flame flower" or "painted leaf".[7]

Scientific illustration of E. pulcherrima, ca. 1880

Euphorbia pulcherrima is a shrub or small tree, typically reaching a height of 0.6–4 metres (2–13 ft). The plant bears dark green dentate leaves that measure 7–16 centimetres (2.8–6.3 in) in length. The colored bracts—which are normally flaming red, with cultivars being orange, pale green, cream, pink, white, or marbled—are often mistaken for flower petals because of their groupings and colors, but are actually leaves.[10][11] The colors of the bracts are created through photoperiodism, meaning that they require darkness (at least fourteen hours at a time for 6–8 weeks in a row) to change color. The plants also require abundant light during the day for the brightest color.[12]

The flowers of the poinsettia are unassuming and do not attract pollinators. They are grouped within the cyathia (small yellow structures found in the center of each leaf bunch, or false flowers).[10] Nothing is known about pollination in wild poinsettias, though wasps are noted to occasionally visit the cyathia.[13] All flowers in the Euphorbiaceae are unisexual (either male or female only), and they are often very small in size. In Euphorbia, the flowers are reduced even more and then aggregated into an inflorescence or cluster of flowers.[14]

Newspaper headline from the Honolulu Star-Bulletin (1913) wrongly alleging that poinsettia is deadly

Poinsettias are popularly, though incorrectly, said to be toxic to humans and other animals.[4] This misconception was spread by a 1919 urban legend of a two-year-old child dying after consuming a poinsettia leaf.[15] In 1944, the plant was included in H. R. Arnold's book Poisonous Plants of Hawaii on this premise. Though Arnold later admitted that the story was hearsay and that poinsettias were not proven to be poisonous, the plant was thus thought deadly. In 1970 the US Food and Drug Administration published a newsletter stating erroneously that "one poinsettia leaf can kill a child", and in 1980 they were prohibited from nursing homes in a county in North Carolina due to this supposed toxicity.[4]

An attempt to determine a poisonous dose of poinsettia to rats failed, even after reaching experimental doses equivalent to consuming 500 leaves, or nearly 1 kg (2.2 lb) of sap.[16] Contact with any part of the plant by children or pets often has no effect, though it may cause nausea, diarrhea, or vomiting if swallowed. External exposure to the plant may result in a skin rash for some.[3] A survey of more than 20,000 calls to the American Association of Poison Control Centers from 1985–1992 related to poinsettia exposure showed no fatalities. In 92.4% of calls, there was no effect from exposure, and in 3.4% of calls there were minor effects, defined as "minimally bothersome".[4] Similarly, a cat or dog's exposure to poinsettias rarely necessitates medical treatment. If ingested, mild drooling or vomiting can occur, or rarely, diarrhea. In rare cases, exposure to the eye may result in eye irritation. Skin exposure to the sap may cause itchiness, redness, or swelling.[17]

The poinsettia occurs in Central America, occurring from Mexico to southern Guatemala. Its range is about 2,000 km (1,200 mi) long, encompassing mid-elevation tropical dry forests. Most wild populations are on Pacific-facing slopes in steep canyons. Populations were once found in rolling hill areas, though many have gone extinct. It has been hypothesized that the inaccessibility of the canyons may protect the wild populations from human disturbance. There is a somewhat anomalous population of wild poinsettias in the northern part of the Mexican state of Guerrero and Oaxaca, which is much further inland in the hot and seasonally dry forests than the rest of the species' range. Genetic analyses showed that the wild populations in northern Guerrero are the likely ancestors of most cultivated poinsettias.[13]

The tropical dry forests where wild poinsettias grow experience largely unregulated deforestation, resulting in habitat loss. Its natural habitat is thus highly fragmented, particularly near metropolitan areas such as Taxco. Population sizes are frequently very small, with as few as a dozen individuals. Populations can be up to several hundred individuals, but this is not typical. A conservation risk typical for species with wild and cultivated populations is the contamination of the wild gene pool by hybridization with cultivated individuals. This has not been documented in wild poinsettias though, as cultivars seldom flower and do not produce fruits. As of 2012, wild poinsettias are not protected by Mexican law.[13]

Poinsettias in a church in the Philippines

Aztec people use the plant to produce red dye and as an antipyretic medication.[10] In Nahuatl, the language of the Aztecs, the plant is called Cuetlaxochitl, meaning "flower that grows in residues or soil"[10] Today it is known in Mexico and Guatemala as flor de Nochebuena, meaning Christmas Eve flower.[10] In Spain it is known as Flor de Pascua or Pascua, meaning Easter flower.[10] In Chile and Peru, the plant became known as Crown of the Andes.[10]

The plant's association with Christmas began in 16th-century Mexico, where legend tells of a girl, commonly called Pepita or María, who was too poor to provide a gift for the celebration of Jesus' birthday and was inspired by an angel to gather weeds from the roadside and place them in front of the church altar.[18] Crimson blossoms sprouted from the weeds and became poinsettias.[19] From the 17th century, Franciscan friars in Mexico included the plants in their Christmas celebrations.[20] The star-shaped leaf pattern is said to symbolize the Star of Bethlehem, and the red color represents the blood sacrifice of Jesus's crucifixion. 'Kingfisher Books' ' 1992's 'The Christmas Collection' notes that an alternative name for the plant is "Fire flowers of the Holy Night".[21]

Poinsettias are popular Christmas decorations[22] in homes, churches, offices, and elsewhere across North America, as a result of an extensive marketing campaign by the Ecke family that began by shipping free poinsettias to television stations for use on-air.[23] In the US, December 12 is National Poinsettia Day, marking the anniversary of Joel Roberts Poinsett's death.[24][25]

Cultivated poinsettia

Poinsettia varieties on sale in England

The Aztecs were the first to cultivate poinsettias.[8] Cultivation in the US began when diplomat Joel Roberts Poinsett sent some of the plants back to his greenhouses in South Carolina in the 1820s. Specific details about its spread from there are largely unverifiable, but it was exhibited at the Pennsylvania Horticultural Society in 1829 by Colonel Robert Carr.[7]

The poinsettia is the world's most economically important potted plant.[13] Each year in the US, approximately 70 million poinsettias are sold in a period of six weeks, at a value of US$250 million.[26] In Puerto Rico, where poinsettias are grown extensively in greenhouses, the industry is valued at $5 million annually.[27] There are over 100 cultivated varieties of poinsettia that have been patented in the US.[28][10][11]

To produce extra axillary buds that are necessary for plants containing multiple flowers, a phytoplasma infection—whose symptoms include the proliferation of axillary buds—is used.[29] The discovery of the role phytoplasmas play in the growth of axillary buds is credited to Ing-Ming Lee of the USDA Agricultural Research Service.[30]

• Christmas in Mexico
• Christmas plants

• Paul Ecke III; James E. Faust; Jack A. Williams; Andy Higgins (Author) (2004). The Ecke Poinsettia Manual. Chicago Review Press. ISBN 978-1883052416.

Wikisource has the text of the 1911 Encyclopædia Britannica article Poinsettia.

• Euphorbia pulcherrima at Wikibooks
• Media related to Euphorbia pulcherrima at Wikimedia Commons