Tradescantia is a genus of 75 species of herbaceousperennial wildflowers in the family Commelinaceae, native to the New World from southern Canada to northern Argentina, including the West Indies. Members of the genus are known by the common namesspiderwort or Indian paint. They were introduced into Europe as ornamental plants in the 17th century and are now grown in many parts of the world. Some species have become naturalized in various regions of Europe, Asia, Africa, and Australia, as well as on some oceanic islands. Tradescantia are weakly-upright to scrambling plants, growing, and are commonly found individually or in clumps in wooded areas and open fields. A number of species have flowers that unfold in the morning and close when the sun shines on the flowers in the afternoon but can remain open on cloudy days until evening. Three species known colloquially as "Wandering Jew", one native to eastern Mexico, also belong to the genus Tradescantia. Other names used for various species include spider-lily, cradle-lily, oyster-plant and flowering inch plant. The genus is of interest to cytogenetics because of evolutionary changes in the structure and number of their chromosomes. In addition to their use as ornamentals, Tradescantia is of economic importance because a number of species have become pests to cultivated crops. They have also been used as bioindicators for the detection of environmental mutagens.
Description
Tradescantia are herbaceous perennials and include both climbing and trailing species, reaching in height. The leaves are long, thin and blade-like to lanceolate, from. The flowers can be white, pink, or purple, but are most commonly bright blue, with three petals and six yellow anthers. The sap is mucilaginous and clear.
Taxonomy
Subdivisions
Phylogenetic studies suggest that Tradescantia can be subdivided into as many as twenty distinct sections, as given here and further circumscribed by Burns et al.. Enlarging the sections from eight to twelve added six further species for a total of 68. Within section Tradescantia, he distinguished the American species from the three Mexican series. "Type" as listed here indicates species typica. Numbering of sections refers to Hunt's original system as a cross check to his index. The renumbered sections from 1986 are given in italics, e.g. .
Tradescantia × andersoniana W.Ludw. & Rohweder Phylogenetically T. x andersoniana is situated within series Virginianae, as follows.
Formerly placed here
Callisia navicularis D.R.Hunt
Callisia warszewicziana D.R.Hunt
Gibasis geniculata Rohweder
Gibasis karwinskyana Rohweder
Gibasis pellucida D.R.Hunt
Siderasis fuscata H.E.Moore
Tinantia anomala C.B.Clarke
Tripogandra diuretica Handlos
Species
By 1998, Fadden listed 70 species, while currently The Plant List accepts 75.
Etymology
The name of the genus by Carl Linnaeus honours the English naturalists and explorers John Tradescant the Elder and John Tradescant the Younger, who introduced many new plants to English gardens. Tradescant the Younger mounted three expeditions to the New Worldcolony of Virginia. From there the type species, Tradescantia virginiana, was brought to England in 1629. The genus Tradescantia has received many common names, varying by region and country. Some of these names refer to the plants' great dispersal ability or invasiveness, such as "Wandering Jew"; the latter, an anti-Semitic name which Tradescantia species share with plants of several other genera, refers to a Christian myth of the Wandering Jew, condemned to wander the earth for taunting Jesus on the way to his crucifixion. In Spanish, it is sometimes referred to as flor de Santa Lucía, in reference to the Saint's reputation as the patron saint of sight, and the use of the juice of the plant as eye drops to relieve congestion.
Distribution and habitat
The first species described, the Virginia spiderwort, T. virginiana, is native to the eastern United States from Maine to Alabama, and Canada in southern Ontario. Virginia spiderwort was introduced to Europe in 1629, where it is cultivated as a garden flower. The natural range of the genus as a whole spans nearly the entire length and width of mainland North America, from Canada through Mexico and Central America, and thrives in a great diversity of temperate and tropical habitats. It is frequently found in thinly wooded deciduous forests, plains, prairies, and healthy fields, often alongside other native wildflowers.
Spiderworts are popular in Europe and North America as ornamental plants. Temperate species are grown as garden plants while tropical species, such as T. zebrina and T. spathacea, are used as house plants. Ease and popularity of cultivation has led to the spread of some species as serious weeds. A common cultivar responsible for most commercially available plants is derived from the naturally occurring interspecific hybridTradescantia × andersoniana, an invalid name more correctly referred to as 'Andersoniana Group' since it includes several cultivars, the origins of which are complex. The group was derived from naturally occurring cross-pollination between Tradescantia virginiana, T. ohiensis, and T. subaspera in overlapping ranges within continental North America. They share a number of characteristics, although they differ in flower colour. The cultivars in this group include 'Blue Stone', 'Isis', 'Innocence', 'Snowcap', 'Osprey', 'Iris Pritchard', 'Pauline', 'Red Cloud' and 'Karminglut'. Tradescantia × andersoniana var. caerulea plena is a double-flowered variety with dark blue flowers.
Weeds
Due to its ready propagation from stem fragments and its domination of the ground layer in many forest environments, T. fluminensis has become a major environmental weed in Australia, New Zealand and the southern United States. Other species considered invasive weeds in certain places include T. pallida, T. spathacea, and T. zebrina.
Toxicity
Some members of the genus Tradescantia may cause allergic reactions in pets characterised by red, itchy skin. Notable culprits include T. albiflora, T. spathacea, and T. pallida.
Uses
s used T. virginiana to treat a number of conditions, including stomachache. It was also used as a food source. The cells of the stamen hairs of some Tradescantia are colored blue, but when exposed to sources of ionizing radiation such as gamma rays, the cells mutate and change color to pink; they are one of the few tissues known to serve as an effective bioassay for ambient radiation levels.
