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Mistletoe is the common name for obligate hemi-parasitic plants in several families in the order Santalales. These plants grow attached to and penetrating within the branches of a tree or shrub by a structure called the haustorium, through which they absorb nutrients from the host plant.
The name was originally applied to Viscum album (European Mistletoe, Santalaceae), the only species native in Great Britain and much of Europe. European mistletoe, Viscum album is readily recognized by its smooth-edged oval evergreen leaves borne in pairs along the woody stem, and waxy white berries in dense clusters of 2 to 6. In America the genus Viscum does not grow wild but the Eastern Mistletoe (in the genus Phoradendron) is similar, but has shorter, broader leaves and longer clusters of 10 or more berries.
Viscum album is a poisonous plant that causes acute gastrointestinal problems including stomach pain, and diarrhea along with low pulse. However, both European Mistletoe and the North American species, Phoradendron serotinum, are commercially harvested for Christmas decorations.
The largest family of Mistletoes, Loranthaceae, has 73 genera and over 900 species. Subtropical and tropical climates have markedly more Mistletoe species; Australia has 85, of which 71 are in Loranthaceae, and 14 in Santalaceae. Parasitism has evolved only nine times in the plant kingdom; of those, the parasitic mistletoe habit has evolved independently five times: Misodendraceae, Loranthaceae, and Santalaceae, including the former separate families Eremolepidaceae and Viscaceae. Although Viscaceae and Eremolepidaceae were placed in a broadly defined Santalaceae by Angiosperm Phylogeny Group II, DNA data indicates that they evolved independently.
Mistletoe plants grow on a wide range of host trees, and commonly reduce their growth and can kill them with heavy infestation. Viscum album can parasitise more than 200 tree and shrub species. All mistletoes are hemi-parasites, bearing evergreen leaves that do some photosynthesis, and using the host mainly for water and mineral nutrients. Mistletoe first sprouts from bird feces on the trunk of the tree and in its early stages of life it takes nutrients from this source. Species more or less completely parasitic include the leafless quintral, Tristerix aphyllus, which lives deep inside the sugar-transporting tissue of a spiny cactus, appearing only to show its tubular red flowers, and the genus Arceuthobium (dwarf mistletoe; Santalaceae) which has reduced photosynthesis; as an adult, it manufactures only a small proportion of the sugars it needs from its own photosythesis but as a seedling it actively photosynthesizes until a connection to the host is established.
Most mistletoe seeds are spread by birds, such as the Mistle Thrush in Europe, the Phainopepla in southwestern North America, and Dicaeum of Asia and Australia. However, distinguishing between these species and ones of other ecological biomes is not difficult. They derive sustenance and agility through eating the fruits and nuts (drupes). The seeds are excreted in their droppings and stick to twigs, or more commonly the bird grips the fruit in its bill, squeezes the sticky coated seed out to the side, and then wipes its bill clean on a suitable branch. The seeds are coated with a sticky material called viscin (containing both cellulosic strands and mucopolysaccharides), which hardens and attaches the seed firmly to its future host.
Once a mistletoe plant has established itself on a branch, the usual treatment is to prune away the branch if it is a small one. However, it usually is possible to save a valuable branch by judicious removal of the wood invaded by the haustorium, if the infection is caught early enough. Some species of mistletoe can regenerate if the pruning leaves any of the haustorium alive in the wood.
Mistletoe was often considered a pest that kills trees and devalues natural habitats, but was recently recognized as an ecological keystone species, an organism that has a disproportionately pervasive influence over its community. A broad array of animals depend on mistletoe for food, consuming the leaves and young shoots, transferring pollen between plants, and dispersing the sticky seeds. In western North America their juicy berries are eaten and spread by birds (notably Phainopepla, or silky-flycatcher). When eaten, some seeds pass unharmed through their digestive systems; if the birds’ droppings happen to land on a suitable branch, the seeds may stick long enough to germinate. This way of propagation is shown in the name: Mistel is the Anglo-Saxon word for dung, and tan is the word for twig; put together this becomes dung-on-a-twig. As the plants mature, they grow into masses of branching stems which suggest the popular name "witches’ brooms". The dense evergreen witches' brooms formed by the dwarf mistletoes (Arceuthobium species) of western North America also make excellent locations for roosting and nesting of the northern spotted owl and the marbled murrelet. The Navajo name for mistletoe is "basket on high." In Australia the diamond firetail and painted honeyeater are recorded as nesting in different mistletoes. This behavior is probably far more widespread than currently recognized; more than 240 species of birds that nest in foliage in Australia have been recorded nesting in mistletoe, representing more than 75% of the resident birds.
A study of mistletoe in junipers concluded that more juniper berries sprout in stands where mistletoe is present, as the mistletoe attracts berry-eating birds which also eat juniper berries. Such interactions lead to dramatic influences on diversity, as areas with greater mistletoe densities support higher diversities of animals. Thus, rather than being a pest, mistletoe can have a positive effect on biodiversity, providing high quality food and habitat for a broad range of animals in forests and woodlands worldwide.
The word 'mistletoe' (Old English mistiltan) is of uncertain etymology; it may be related to German Mist, for dung and Tang for branch, since mistletoe can be spread in the droppings of birds moving from tree to tree. However, Old English mistel was also used for basil.
Because of the scheming of Loki, according to the 13th century Prose Edda, the god Baldr is killed by his brother, the blind god Höðr, by way of a mistletoe projectile, despite the attempts of Baldr's mother, the goddess Frigg, to have all living things and inanimate objects swear an oath not to hurt Baldr after Baldr had troubling dreams of his death. Frigg was unable to get an oath from mistletoe, because "it seemed too young" to demand an oath from. In the Gesta Danorum version of the story, Baldr and Höðr are rival suitors, and Höðr kills Baldr with a sword named Mistilteinn (Old Norse "mistletoe"). In addition, a sword by the same name appears in various other Norse legends.
In cultures across pre-Christian Europe, mistletoe was seen as a representation of divine male essence (and thus romance, fertility and vitality).
When Christianity became widespread in Europe after the 3rd century AD, the religious or mystical respect for the mistletoe plant was integrated to an extent into the new religion. In some way that is not presently understood, this may have led to the widespread custom of kissing under the mistletoe plant during the Christmas season. The earliest documented case of kissing under the mistletoe dates from 16th century England, a custom that was apparently very popular at that time.
Mistletoe is commonly used as a Christmas decoration, though such use was rarely alluded to until the 18th century. Viscum album is used in Europe whereas Phoradendron serotinum is used in North America. According to custom, the mistletoe must not touch the ground between its cutting and its removal as the last of Christmas greens at Candlemas; it may remain hanging through the year, often to preserve the house from lightning or fire, until it is replaced the following Christmas Eve. The tradition has spread throughout the English-speaking world but is largely unknown in the rest of Europe.
The type of Mistletoe used during Christmas celebrations is of the same type as that believed to be sacred by ancient druids, but, outside northern Europe, the plant used is not the same species. The mistletoe that is commonly used as a Christmas decoration in North America (Phoradendron flavescens) grows as a parasite on trees in the west as also in those growing in a line down the east from New Jersey to Florida. In Europe, where the custom originates, the 'original' mistletoe, Viscum album, is still used. The European mistletoe is a green shrub with small, yellow flowers and white, sticky berries which are considered poisonous. Ancient druids considered the Viscum album plant holy, but had no knowledge of the Phoradendron flavescens. Modern druids focus on the parasitic habitat on oak (where it is very rarely found) as being the definer of a sacred mistletoe, and use Phoradendron flavescens as well as other mistletoe species.
According to ancient Christmas custom, a man and a woman who meet under a hanging of mistletoe were obliged to kiss. The custom may be of Scandinavian origin. It was described in 1820 by American author Washington Irving in his "The Sketch Book of Geoffrey Crayon":
See also The Holly and the Ivy.
Mistletoe (Phoradendron serotinum) is the state floral emblem for the state of Oklahoma. The state did not have an official flower, leaving mistletoe as the assumed state flower until the Oklahoma Rose was designated as such in 2004.
Available clinical evidence does not support claims of anti-cancer effect, quality of life, or other outcomes from the use of mistletoe extract. Research has likewise shown little or no improvement in rigorous trials. Public interest in the United States was spurred in 2001 following actress Suzanne Somers' decision to use Iscador in lieu of chemotherapy following her treatment for breast cancer using surgery and radiotherapy.
Mistletoe leaves and young twigs are used by herbalists, and it is popular in Europe, especially in Germany, for treating circulatory and respiratory system problems. Use of mistletoe extract in the treatment of cancer originated with Rudolf Steiner, the founder of Anthroposophy. He compared the parasitic nature of the mistletoe plant to that of cancer, and believed that cancer represents a faltering of the body's spiritual defenses. Some anthroposophical mistletoe preparations are diluted homeopathically. Mistletoe extract is sold as Iscador, Helixor, and several other trade names.
The sticky juice of mistletoe berries was used as adhesive to trap small animals or birds. In South Africa it is called "bird lime" in English and voëlent in Afrikaans. A handful of ripe fruits are chewed until sticky, and the mass is then rubbed between the palms of the hands to form long and extremely sticky strands which are then coiled around small thin tree branches where birds perch. When a bird lands on this it gets stuck to the branch and is then easy to catch by hand.
|Wikimedia Commons has media related to: Mistletoe|
Mistletoe bush on a Eucalyptus tree
Mistletoe attached to Eucalyptus host
Mistletoe in San Bernardino Mountains
Mistletoe berries in Wye Valley
Mistletoe in abundance in Wye Valley
Mistletoe in North Central Texas
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