Ruppius ex L.
Tradescantia // is a genus of 75 species of herbaceous perennial 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 name spiderwort. They were introduced into Europe as ornamental plants in the 17th century and are now grown as such in many parts of the world. Subsequently, 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 30–60 cm tall (0.98–1.97 ft), 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 Tradescantia genus. 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.
Tradescantia are herbaceous perennials and include both climbing and trailing species, reaching 30–60 centimetres (0.98–1.97 ft) in height. The leaves are long, thin and blade-like to lanceolate, from 3–45 cm long (1.2–17.7 in). The flowers can be white, pink, or purple, but are most commonly bright blue, with three petals and six yellow anthers (or rarely, four petals and eight yellow anthers). The sap is mucilaginous and clear.
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. (2011).
Enlarging the sections from eight to twelve added six further species for a total of 68. Within section Tradescantia, he distinguished the American species (series Virginianae) from the three Mexican series (Tuberosae, Sillamontanae, and Orchidophyllae). "Type" as listed here indicates species typica. Numbering of sections refers to Hunt's original (1980) system as a cross check to his index. The renumbered sections from 1986 are given in italics, e.g. (1)(5).[a][b]
(Brazil, Uruguay, N Argentina)
(Guatemala, El Salvador, S Mexico)
(S Mexico, Guatemala, Nicaragua and Costa Rica)
(Mexico to Bolivia and Brazil)
(Mexico: Chihuahua to Oaxaca)
(Mexico (Yucatán), Belize)
(U.S.A.: Texas; Mexico: Chihuahua to Veracruz)
(Mexico to Venezuela)
- Tradescantia × andersoniana W.Ludw. & Rohweder  Phylogenetically T. x andersoniana is situated within series Virginianae, as follows ( T. ohiensis × ( T. subaspera Ker Gawl. × T. virginiana L.)).
Formerly placed here
- Callisia navicularis (Ortgies) D.R.Hunt (as T. navicularis Ortgies)
- Callisia warszewicziana (Kunth & C.D.Bouché) D.R.Hunt (as T. warszewicziana Kunth & C.D.Bouché)
- Gibasis geniculata (Jacq.) Rohweder (as T. geniculata Jacq.)
- Gibasis karwinskyana (Schult. & Schult.f.) Rohweder (as T. karwinskyana Schult. & Schult.f.)
- Gibasis pellucida (M.Martens & Galeotti) D.R.Hunt (as T. pellucida M.Martens & Galeotti)
- Siderasis fuscata (Lodd. et al.) H.E.Moore (as T. fuscata Lodd. et al.)
- Tinantia anomala (Torr.) C.B.Clarke (as T. anomala Torr.)
- Tripogandra diuretica (Mart.) Handlos (as T. diuretica Mart.)
The name of the genus by Carl Linnaeus honours the English naturalists and explorers John Tradescant the Elder (c. 1570s – 1638) and John Tradescant the Younger (1608–1662), who introduced many new plants to English gardens. Tradescant the Younger mounted three expeditions to the New World colony 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, 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 (Saint Lucy's flower), 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.
The western spiderwort T. occidentalis is listed as an endangered species in Canada, where the northernmost populations of the species are found at a few sites in southern Saskatchewan, Manitoba and Alberta; it is more common further south in the United States to Texas and Arizona.
Though sometimes considered a weed, spiderwort is a popular ornamental plant cultivated for borders and also used in containers. Where it appears as a volunteer, it is often welcomed and allowed to stay. Temperate species are grown as garden plants while tropical species such as T. zebrina and T. spathacea are used as house plants.
A common cultivar responsible for most commercially available plants is derived from the naturally occurring interspecific hybrid (nothospecies) Tradescantia × 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' ('Carmine Glow'). Tradescantia × andersoniana var. caerulea plena is a double-flowered variety with dark blue flowers.
Some members of the genus Tradescantia may cause allergic reactions in pets (especially cats and dogs) characterised by red, itchy skin. Notable culprits include T. albiflora (Scurvy Weed), T. spathacea (Moses In The Cradle), and T. pallida (Purple Heart).
American Indians used T. virginiana to treat a number of conditions, including stomachache and cancer. 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.
Front view of leaves of Tradescantia pallida cv. "Purple Heart".
Back view of leaves of Tradescantia pallida cv. "Purple Heart".
Front view of leaves of Tradescantia zebrina cv. "Tricolor".
Back view of leaves of Tradescantia zebrina cv. "Tricolor".
- The place of T. schippii is uncertain. Hunt indicates it is included in section Zebrina, but Burns considers the section monotypic.
- T. blossfeldiana as used by Hunt and Burns is now considered a synonym for T. cerinthoides. Hunt originally listed these as separate species. Hunt also listed T. potosina and T. nuevoleonensis as separate species, but the latter is now the accepted name, while T. subramosa and T. subtilis are now considered synonyms for T. maysillesii rather than separate species.
- Linnaeus Sp. Pl.: 288 (1753).
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- Burns, Jean H.; Faden, Robert B.; Steppan, Scott J. (2011). "Phylogenetic Studies in the Commelinaceae Subfamily Commelinoideae Inferred from Nuclear Ribosomal and Chloroplast DNA Sequences". Systematic Botany. 36 (2): 268–276. doi:10.1600/036364411X569471.
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- Edgar, Anderson; Karl, Sax (March 1936). "A Cytological Monograph of the American Species of Tradescantia". Botanical Gazette. 97 (3): 433–476. JSTOR 2471708. doi:10.1086/334582.
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