Poinsettia (plant)

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Christmas star
Poinsettia (Euphorbia pulcherrima)

Poinsettia ( Euphorbia pulcherrima )

Systematics
Rosids
Eurosiden I
Order : Malpighiales (Malpighiales)
Family : Spurge Family (Euphorbiaceae)
Genre : Spurge ( Euphorbia )
Type : Christmas star
Scientific name
Euphorbia pulcherrima
Willd. ex Klotzsch

The poinsettia ( Euphorbia pulcherrima ), also Adventsstern , Christstern or Poinsettie called, is a species of the genus spurge ( Euphorbia ) in the family of Euphorbiaceae (Euphorbiaceae). The specific epithet pulcherrima is derived from Latin and means "the most beautiful". Poinsettias are due to abnormal, intensely colored bracts (bracts), which are arranged in a star shape, popular house plants. The bracts are often mistaken for bracts.

description

illustration
Detail of the inflorescence of a poinsettia, with red bracts and yellow-green cyathia
Cyathium with many male flowers and lip-shaped nectar glands
Cyathium with many male flowers, lip-shaped nectar glands and the single, large female flower with ovary and stigma

Euphorbia pulcherrima is a rare wild plant with occurrences along the Pacific coast of Central America. The cultivated ornamental plants are cultivars and differ in many characteristics from the wild form. These ornamental plants are rewilded almost worldwide in regions with a climate comparable to the region of origin; these neophytic occurrences do not fully correspond in terms of their characteristics to the real wild occurrences.

Appearance and foliage leaf

Euphorbia pulcherrima is an evergreen or partially deciduous shrub or small tree with a woody trunk and twigs and sparse branches that can grow up to 4 m, exceptionally 5 m. Plants cultivated in horticulture, on the other hand, are usually much smaller and more or less strongly branched. The real wild form has an elongated, often completely unbranched trunk with scattered leaves with long internodes .

As typical and eponymous for the genus, the plants contain white milky sap . Young plants have thickened, juicy roots and are generally weakly succulent . The cylindrical branches are smooth. The slightly hairy leaves are alternate, often opposite or heaped in whorls below the inflorescences. The petiole is 2.5 to 5, rarely up to 8 cm long. The simple leaf blade is variable, with a length of 6 to 25 cm and a width of 4 to 10 (-12) cm (even larger if it is dark), elliptical to obovate with a wedge-shaped base and blunt to long pointed tip, often Violin-shaped (with two pointed, lateral lobes, which are separated by a semicircular constriction in the middle), in cultivated forms the leaf margin is often slightly serrated. The top of the leaves is dark green while the underside is lighter.

Inflorescence and flower

The poinsettia blooms as a wild plant in the winter dry season, when it has often shed most of the leaves. The main flowering period is from November to January or February. Depending on the location, cultivated older branched poinsettias also bloom almost all year round. They are so-called short - day plants that only set flowers when they have not received more than 12 hours of light. This is the case all year round at locations not far from the equator . In Central Europe , the dark phase is artificially extended to at least 12 hours with dark foils in nurseries from around October, so that the plants develop colored bracts in time for Advent . By manipulating the light / dark phases in the greenhouse, poinsettias can also be made to bloom at other times. These are then offered in stores with different names such as autumn star and winter star, depending on the flower formation.

The actual flowers are green-yellowish, small and inconspicuous and not to be confused with the large, bright red bracts ( bracts , cyathophylls) in the middle of which they are located. In wild forms, the bracts are narrowly elliptical, in cultivated poinsettias broadly lanceolate; even in wild ones, they are bright to dirty red, sometimes pink to white. What, like all milkweed species, including the poinsettia as a single flower looks is an inflorescence , the cyathium (plural cyathia) is called. Each individual flower in the Cyathium is unisexual, either only female or only male, there are no cladding sheets . The single flowers are reduced to the bare essentials. In the compound inflorescence there is always only one cyathium with a female flower in the center, which consists only of a stalked triple ovary and the three pistils. The male flowers are arranged in groups around the female flower. These each consist of a single stalked stamen . The nectar glands on the outer edge of the cyathium can be recognized, which occur individually or in pairs in the poinsettia and are lip-shaped. The cyathia sit in dense, richly branched inflorescences of a higher order, which are mostly terminal.

The bracts are used to attract pollinators. Which animal species actually pollinate poinsettias in the natural area has remained unknown to this day. Breeding has resulted in a wide variety of colors. In addition to red tones, there are also salmon-colored, variegated or white (creamy white - not pure white). Other colors such as blue, on the other hand, are artificial and are created by spraying with plant-friendly varnish, or sprinkling a little glitter over them.

Chromosome number

The number of chromosomes is 2n = 26, 28, 42 or 44.

distribution

The natural range of the poinsettia is in western Central America, from Sinaloa in northwestern Mexico to southern Guatemala . It extends in several small island-shaped distribution areas in the coastal mountains at medium altitudes along the Pacific coast with an offshore spur to the east in Guerrero in central Mexico. From this region near the city of Taxco come the plants that Poinsett exported to North America and to which today's cultivars ultimately go back. Since the plant was cultivated as an ornamental plant even before the arrival of the Europeans, the status of some occurrences is unclear. Wild occurrences in central Mexico and Guatemala exist up to heights of about 1000 meters. It grows as a wild plant in the shelter of subtropical dry forests on steep rocky slopes, often on the edge of small ravines. The individual occurrences are scattered and often poor in individuals.

Introduced into other tropical and subtropical regions as an ornamental plant , it has often been overgrown. Larger populations are known in Africa (for example in Kenya , Tanzania and Uganda ), in Asia (for example in Burma , Malaysia and the Philippines ), Australia , and rarely also in the Mediterranean region .

Botanical history

The first reports about the plant reached Europe through Francisco Hernandez de Toledo , natural scientist and doctor in the service of the Spanish King Philip II. In his work Rerum medicarum Novae Hispaniae thesaurus from 1561 there is a description as well as illustrations, simple woodcuts. According to its tradition in Francisci Hernandi Opera cum edita, tum inedita, ad autographi fidem et integritatem expressa of 1790, the poinsettia in Nahuatl (among the Aztecs ) was called Cuetlaxochitl (actually cuetlax-xōchitl , leather flower). More precise descriptions come from a Spanish botanical research trip up to 1803 by Martín Sessé y Lacasta and José Mariano Mociño . Among the extensive material that they sent to Europe, there are some herbarium specimens of a species called Euphorbia fastuosa that have survived to this day and which, according to later knowledge, was the poinsettia. A detailed illustration was forgotten and only found and published centuries later. In 1803, Alexander von Humboldt and Aimé Bonpland reached Mexico on their trip to South America. Although there is no mention of the species in their works, two documents have been preserved in the Berlin herbarium that go back to this expedition.

The name poinsettia, which is still occasionally used by gardeners, comes from the earlier botanical genus name poinsettia . This name Poinsettia goes back to the American ambassador to Mexico , Joel Roberts Poinsett , who discovered this plant species as an ornamental plant at the beginning of the 19th century during a trip with members of a scholarly society from Philadelphia in 1825 in the area of ​​Taxco (Guerrero) and introduced to the United States in 1828 or 1829 . It is reported by some authors that Poinsett, who had some botanical knowledge, first cultivated the plants in his South Carolina greenhouses. They got either from there or, far more likely, directly from Mexico to the Bartram Botanical Garden of John Bartram in Philadelphia, from where the plant dealer Robert Buist introduced them to Europe in 1834. According to American plants in the Bartrams' garden, the species was first described in 1833 by Constantine S. Rafinesque-Schmaltz as Pleuradenia coccinea (alternatively, if placed in the genus Euphorbia , also Euphorbia coccinea or Euphorbia poinsettii ), this name was later, possibly erroneously, as not suppressed according to the rules described. In 1833 the Hungarian-German botanist Wilhelm Friedrich von Karwinsky von Karwin sent from a trip to Mexico from 1827 to 1832 both herbarium specimens and living plants to Munich, which came to the Berlin Botanical Garden in 1833 . Here they were first described as valid Euphorbia pulcherrima by Johann Friedrich Klotzsch , doctor, pharmacist and curator at the Botanical Museum, in 1834 according to a document from the "Willdenow" herbarium in the Allgemeine Gartenzeitung . Klotzsch ascribed the name to the botanist Carl Ludwig Willdenow , who is said to have coined it in an unpublished manuscript. In 1836 the Scottish botanist Robert Graham put the species into its own genus Poinsettia , based on material he had received from Philadelphia, and named it Poinsettia pulcherrima . Today the name is only used for a section (some botanists: a subgenus) of the genus Euphorbia .

Phylogeny and Systematics

The poinsettia belongs within the genus Euphorbia to the subgenus Chamaesyce . This includes around 600 species with a distribution center in the New World. It forms with a number (about 25) related species the section Poinsettia (Graham) Baill., Which is characterized morphologically by the loss of the appendages of their cup-shaped nectar glands and by the colored bract around the crowded inflorescences. Euphorbia pulcherrima is their type . The togetherness of the species (and thus the monophyly of the taxon) was supported by genetic studies.

Breeding and cultivation

At the beginning of the 20th century, the German emigrant family Ecke established the poinsettia as a "Christmas flower" in California. The widely used manual The Poinsettia Manual goes back to their descendants . Initially, the star was offered as a cut flower. Breeding programs from Pennsylvania State University, the USDA Research Center in Beltsville, Maryland, and the University of Maryland, along with the efforts of Eckes and other private breeders, improved the properties; the original plants usually only retained their spectacular red bracts for about 10 days and lost most of their leaves before flowering. Around 1980, an American breeder discovered that the desired dense plants could be produced by grafting newly grown, weakly branched plants with the desired properties onto heavily branched bases, which revolutionized breeding; later it was found that the effect is due to the transfer of phytoplasms . In addition to American breeders, the former Hillscheid-based floriculture company Fischer also achieved great success in establishing new varieties.

The poinsettia is particularly popular as a houseplant , in Central Europe since around 1950. The cuttings often come from Africa by plane and are only cultivated to the end at their destination. The poinsettia comes in various growth forms such as single, multiple shoots or as a high stem for Advent when it has set flowers that are surrounded by the colored bracts. The poinsettia thrives best under bright but indirect lighting, and strong direct sunlight on the leaves should be avoided. The plant is not hardy and suffers even from short-term exposure to cool temperatures; this often leads to failure after cold transport. Blooming poinsettias should be watered well without the risk of stagnant moisture. Fertilization during flowering is unnecessary.

Most poinsettias are discarded after they have faded, although they can still be reused. To do this, the upper section of the shoot with the flowers should be cut back after blooming, so that three or four leaves remain. Later on, long shoots can be pruned back about every six weeks for an appealing shape, the last time around the end of August. The plant should be placed in a bright location with the most uniform possible temperature above 17 ° C. From around the first of October, the exposure must be reduced in order to stimulate the short-day plant to bloom; a minimum of 12, better 14 hours of uninterrupted darkness are required, if possible without any stray light or interference.

The “autumn star ” is the cultivar Euphorbia 'Princettia', bred from a hybrid Euphorbia pulcherrima x Euphorbia cornastra (a very rare endemic of the Mexican Sierra Madre del Sur with pure white bracts that was discovered in the wild in 1975 Hybrid salmon pink hues).

Toxicology and Toxicity

As is typical for the genus Euphorbia , the poinsettia contains poisonous milky sap. In the past, however, the poisonous effects of the species were in some cases far overestimated. By evaluating a data series running over eight years at the American Association of Poison Control Centers, it was possible to show that of over 22,000 evaluated reported cases of poisoning, over 93 percent affected children, about 77 percent of them under two years of age. Around 95 percent involved ingestion of parts of plants. No symptoms were registered in 92.4% of the cases. 96.1% of the patients could be sent home without medical treatment. There were no serious cases of poisoning, let alone death. Mild irritation after skin contact was most frequently observed. Contact dermatitis and vomiting, diarrhea, or nausea are the most severe symptoms to expect. As first aid it is recommended: Drink plenty. If large amounts of coal are consumed, give a doctor if necessary.

Individual evidence

  1. ↑ a b c Laura Trejo, Teresa Patricia Feria Arroyo, Kenneth M. Olsen, Luis E. Eguiarte, Baruch Arroyo, Jennifer A. Gruhn, Mark E. Olson (2012): Poinsettia's wild ancestor in the Mexican dry tropics: Historical, genetic , and environmental evidence. American Journal of Botany 99 (7): 1146-1157. doi: 10.3732 / ajb.1200072
  2. ↑ Ma Jinshuang (马 金 双), Michael G. Gilbert: Euphorbia. Flora of China 11 (2008): 288-313. online at www.efloras.org .
  3. ^ A. Radcliffe-Smith: Euphorbia. Flora of Pakistan. online at www.efloras.org .
  4. ↑ Euphorbia pulcherrima, Poinsettia. HortFlora Horticultural Flora of South-eastern Australia .
  5. ^ A b Paul Carpenter Standley, Julian Alfred Steyermark: Flora of Guatemala. Fieldiana Botany Series 24 (6). published by Chicago Natural History Museum, 1949. Full text at www.biodiversitylibrary.org .
  6. ^ William Burger, Michael Huft: Euphorbiaceae. Flora costaricensis. Fieldiana Botany, New Series 36. published by Field Museum of Natural History, 1995.
  7. ↑ Euphorbia pulcherrima at Tropicos.org. In: IPCN Chromosome Reports . Missouri Botanical Garden, St. Louis
  8. ^ A b H. Walter Lack (2011): The discovery, naming and typification of Euphorbia pulcherrima (Euphorbiaceae). Willdenowia, 41 (2): 301-309. doi: 10.3372 / wi.41.41212
  9. ^ A b Judith M. Taylor, Roberto G. Lopez, Christopher J. Currey, Jules Janick (2011): The Poinsettia: History and Transformation. Chronica Horticulturae 51 (3): 23-28.
  10. ↑ D. Michael Benson, Janet L. Hall, Gary W. Moorman, Margery L. Daughtrey, Ann R. Chase, Kurt H. Lamour (2002): The History and Diseases of Poinsettia, the Christmas Flower. Plant Health Progress 3 (1) PDF
  11. ↑ Ya Yang, Ricarda Riina, Jeffery J. Morawetz, Thomas Haevermans, Xavier Aubriot, Paul E. Berry (2012): Molecular phylogenetics and classification of Euphorbia subgenus Chamaesyce (Euphorbiaceae). Taxon 61 (4): 764-789. doi: 10.1002 / tax.614005
  12. ↑ Isabel Strassheim: Migros Christmas stars “from the region” come from Africa. In: bazonline.ch . December 9, 2019, accessed December 10, 2019 .
  13. ^ SE Newman and BE Edmunds: Poinsettias. Fact Sheet No. 7,412, Gardening Series. Colorado State University Extension 10/98.
  14. ↑ Annette Höggemeier (2014): Euphorbia pulcherrima - Poinsettia (Euphorbiaceae). Yearbook of the Bochum Botanical Association 5: 189–190.
  15. ↑ Euphorbia Princettia in the Plants Database, National Gardening Association, accessed on 14 December of 2019.
  16. ↑ Amber Yang: The Dark Myth of the Poinsettia . Scitable January 1, 2015.
  17. ↑ Edward P. Krenzelok, TD Jacobsen, John M. Aronis (1996): Poinsettia exposures have good outcomes ... just as we thought. American Journal of Emergency Medicine 14 (7): 671-674. doi: 10.1016 / S0735-6757 (96) 90086-8
  18. ^ Judith A. Alsop, John F. Karlik (2016): Poisonous Plants. University of California, Agriculture and Natural Resources, ANR Publication 8560. doi: 10.3733 / ucanr.8560 online
  19. ↑ Poinsettia (Euphorbia pulcherrima). Center for paediatrics, information center against poisoning . University Hospital Bonn. accessed on August 27, 2019.

Web links

Commons : Poinsettia ( Euphorbia pulcherrima )  - album with pictures, videos and audio files