Viola (Template:IPAc-en and Template:IPAc-en)<ref>The pronunciation Template:IPAc-en (Template:Respell) is the most common one in US English, but US dictionaries also record (less common) use of Template:IPAc-en (Template:Respell) and Template:IPAc-en (Template:Respell): American Heritage Dictionary Template:Webarchive, Merriam-Webster Online Dictionary Template:Webarchive. The only pronunciation recorded by the Compact Oxford English Dictionary is Template:IPAc-en (Template:Respell) but the only pronunciation recorded by the Oxford Dictionaries Online is Template:IPAc-en (Template:Respell).</ref> is a genus of flowering plants in the violet family Violaceae. It is the largest genus in the family, containing between 525 and 600 species.<ref name=ning>Template:Cite journal</ref><ref name=zhou>Template:Cite journal</ref> Most species are found in the temperate Northern Hemisphere; however, some are also found in widely divergent areas such as Hawaii, Australasia, and the Andes.
Some Viola species are perennial plants, some are annual plants, and a few are small shrubs. A large number of species, varieties and cultivars are grown in gardens for their ornamental flowers. In horticulture the term "pansy" is normally used for those multi-coloured, large-flowered cultivars which are raised annually or biennially from seed and used extensively in bedding. The terms "viola" and "violet" are normally reserved for small-flowered annuals or perennials, including the species.<ref name="americanvioletsociety.org">Template:Cite web (Accessed 14 Oct 2008)</ref><ref>Template:Cite web (Accessed 14 Oct 2008)</ref>
- 1 Description
- 2 Selected species
- 3 Horticultural uses
- 4 Ecology
- 5 Weed control
- 6 Other uses
- 7 See also
- 8 References
Viola typically have heart-shaped, scalloped leaves, though a number have palmate leaves or other shapes. The vast majority of Viola species are herbaceous, and a substantial number are acaulescent in habit - meaning they lack any noticeable stems and the foliage and flowers appear to rise from the ground; the remaining species have short stems with foliage and flowers produced in the axils of the leaves. The simple leaves of plants with either habit are arranged alternately; the acaulescent species produce basal rosettes. Plants always have leaves with stipules that are often leaf-like.flowers of the vast majority of the species are zygomorphic with bilateral symmetry. The flowers are formed from five petals; four are upswept or fan-shaped petals with two per side, and there is one broad, lobed lower petal pointing downward. The shape of the petals and placement defines many species, for example, some species have a "spur" on the end of each petal while most have a spur on the lower petal.
Solitary flowers end long stalks with a pair of bracteoles. The flowers have 5 sepals that persist after blooming, and in some species the sepals enlarge after blooming. The flowers have five free stamens with short filaments that are oppressed against the ovary, only the lower two stamens have nectary spurs that are inserted on the lowest petal into the spur or a pouch. The flower styles are thickened near the top and the stigmas are head-like, narrowed or often beaked. The flowers have a superior ovary with one cell, which has three placentae, containing many ovules.
Viola are most often spring blooming with chasmogamous flowers with well-developed petals pollinated by insects. Many species also produce self-pollinated cleistogamous flowers in summer and autumn that do not open and lack petals.<ref>Walters, Dirk R., and David J. Keil. 1996. Vascular plant taxonomy. Dubuque, Iowa: Kendall/Hunt Pub. Co. Page 332.</ref> In some species the showy chasmogamous flowers are infertile (e.g.,Viola papilionacea).<ref>Violet, Common Blue - (‘’Viola papilionacea’’) Template:Webarchive</ref>
After flowering, fruit capsules are produced that split open by way of three valves.<ref>Cullen, J. 2001. Handbook of North European garden plants with keys to families and genera. Cambridge: Cambridge University Press. Page 345.</ref> On drying, the capsules may eject seeds with considerable force to distances of several meters.<ref>Rendle, Alfred B. 1967. The classification of plants. Vol. II: Dicotyledons. Cambridge at the University Press. (See page 208).</ref> The nutlike seeds have straight embryos, flat cotyledons, and soft fleshy endosperm that is oily.<ref>Cronquist, Arthur. 1981. An integrated system of classification of flowering plants. New York: Columbia University Press. Page 404.</ref> The seeds of some species have elaiosomes and are dispersed by ants.<ref>Sanders, Jack. 2003. The secrets of wildflowers. Guilford, CT: The Globe Pequot Press. (See page 49).</ref>
Flower colours vary in the genus, ranging from violet, through various shades of blue, yellow, white, and cream, whilst some types are bicolored, often blue and yellow. Flowering is often profuse, and may last for much of the spring and summer.
One quirk of some Viola is the elusive scent of their flowers; along with terpenes, a major component of the scent is a ketone compound called ionone, which temporarily desensitises the receptors of the nose, thus preventing any further scent being detected from the flower until the nerves recover.Template:Citation needed
See List of Viola species for a more complete list.
The genus includes dog violets, a group of scentless species which are the most common Viola in many areas, sweet violet (Viola odorata) (named from its sweet scent), and many other species whose common name includes the word "violet". Several species are known as pansies, including the yellow pansy (Viola pedunculata) of the Pacific coast.
Species and cultivars
Cultivars of Viola cornuta, Viola cucullata, and Viola odorata, are commonly grown from seed. Other species often grown include Viola labradorica, Viola pedata, and Viola rotundifolia.<ref name="Armitage1989">Template:Citation</ref>
In 2005 in the United States, Viola cultivars (including pansies) were one of the top three bedding plant crops and 111 million dollars worth of flats of Viola were produced for the bedding flower market.<ref>Template:Cite web</ref> Pansies and violas used for bedding are generally raised from seed, and F1 hybrid seed strains have been developed which produce compact plants of reasonably consistent flower colouring and appearance. Bedding plants are usually discarded after one growing season.
There are hundreds of perennial viola and violetta cultivars; many of these do not breed true from seed and therefore have to be propagated from cuttings. Violettas can be distinguished from violas by the lack of ray markings on their petals.<ref name="americanvioletsociety.org"/> The following cultivars have gained the Royal Horticultural Society's Award of Garden Merit:-
- 'Aspasia'<ref>Template:Cite web</ref>
- 'Clementina'<ref>Template:Cite web</ref>
- 'Huntercombe Purple'<ref>Template:Cite web</ref>
- 'Moonlight'<ref>Template:Cite web</ref>
- 'Nellie Britton'<ref>Template:Cite web</ref>
Other popular examples include:<ref>RHS Plant Finder 2008-2009, Dorling Kindersley (2008) Template:ISBN pp787–791</ref>
Viola species are used as food plants by the larvae of some Lepidoptera species, including the giant leopard moth, large yellow underwing, lesser broad-bordered yellow underwing, high brown fritillary, small pearl-bordered fritillary, pearl-bordered fritillary, cardinal, and Setaceous Hebrew character.
Not all Viola are desired, and wild violets are considered weeds in North American lawns by some people.Template:Citation needed Others tolerate or welcome the presence of violets in lawns. Wild violets are regarded as a problem in shady fescue lawns in North America. Violets thrive in the part/full shade and are not susceptible to most herbicides used to kill common lawn weeds. Triclopyr, a weedkiller, has been found to be an effective method of controlling wild violets in fescue lawns.
When newly opened, Viola flowers may be used to decorate salads or in stuffings for poultry or fish. Soufflés, cream, and similar desserts can be flavoured with essence of Viola flowers. The young leaves are edible raw or cooked as a somewhat bland leaf vegetable. The flowers and leaves of the cultivar 'Rebecca', one of the Violetta violets, have a distinct vanilla flavor with hints of wintergreen. The pungent perfume of some varieties of V. odorata adds inimitable sweetness to desserts, fruit salads, and teas while the mild pea flavor of V. tricolor combines equally well with sweet or savory foods, like grilled meats and steamed vegetables. The heart-shaped leaves of V. odorata provide a free source of greens throughout a long growing season.<ref>Template:Cite web</ref>
A candied violet or crystallized violet is a flower, usually of Viola odorata, preserved by a coating of egg white and crystallised sugar. Alternatively, hot syrup is poured over the fresh flower (or the flower is immersed in the syrup) and stirred until the sugar recrystallizes and has dried. This method is still used for rose petals and was applied to orange flowers in the past (when almonds or orange peel are treated this way they are called pralines). Candied violets are still made commercially in Toulouse, France, where they are known as violettes de Toulouse. They are used as decorating or included in aromatic desserts.
In the United States, the violet is state flower of Illinois<ref>Template:Cite web</ref> and Rhode Island.<ref>Template:Cite web</ref> Viola sororia was declared the state flower of New Jersey <ref>Template:Cite web</ref> and Wisconsin.<ref>Template:Cite web</ref><ref>Template:Cite web</ref> In Canada, the Viola cucullata is the provincial flower of New Brunswick adopted in 1936<ref>Template:Cite web</ref> In the United Kingdom, Viola riviniana is the county flower of Lincolnshire.<ref>Template:Cite web</ref>
Violets became symbolically associated with lesbian love.<ref>Template:Cite book</ref><ref>Template:Cite book</ref> This connection originates from fragments of a poem by Sappho about a lost love, in which she describes her as "Close by my side you put around yourself [many wreaths] of violets and roses."<ref>Template:Cite book</ref> In another poem, Sappho describes her lost love as wearing "violet tiaras, braided rosebuds, dill and crocus twined around" her neck.<ref>Template:Cite book (LCCN 58-6520)</ref> In 1926, one of the first plays to involve a lesbian relationship, La Prisonnière by Édouard Bourdet, used a bouquet of violets to signify lesbian love.<ref>Template:Cite web</ref><ref>Template:Cite book</ref>
Violets, and badges depicting them,<ref>NMA Collections Search Template:Webarchive National Museum of Australia (2003-2010) - Violet Day 1917 fundraising badge</ref><ref name="Gracie2012">Template:Citation</ref> were sold in fund-raising efforts in Australia and New Zealand on and around Violet Day<ref>Family History South Australia Template:Webarchive Leadbeater, B (2006). World War 1 Violet Day South Australia.</ref> in commemoration of the lost soldiers of World War I.<ref>Template:Cite web</ref>
Many Viola species contain antioxidants called anthocyanins. Fourteen anthocyanins from V. yedoensis and V. prionantha have been identified. Some anthocyanins show strong antioxidant activities.<ref>Template:Cite journal</ref> Most violas tested and many other plants of the family Violaceae contain cyclotides,<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref><ref>Template:Cite journal</ref> which have a diverse range of in vitro biological activities when isolated from the plant, including uterotonic, anti-HIV, antimicrobial, and insecticidal activities.<ref>Template:Cite journal</ref> Viola canescens, a species from India, exhibited in vitro activity against Trypanosoma cruzi.<ref>Template:Cite journal</ref>
Viola has been evaluated in different clinical indications in human studies. A double blind clinical trial showed that the adjuvant use of Viola odorata syrup with short-acting β-agonists can improve the cough suppression in children with asthma.<ref>Template:Cite journal</ref><ref name="PDR for Herbal Medicines">Template:Cite book</ref><ref>Template:Cite journal</ref><ref>Template:Cite journal</ref> In another study intranasal administration of Viola odorata extract oil showed to be effective in patients with insomnia.<ref name="PDR for Herbal Medicines"/><ref>Template:Cite journal</ref> Topical use of an herbal formulation containing Viola tricolor extract also showed promising effects in patients with mild-to-moderate atopic dermatitis.<ref>Template:Cite journal</ref>
Viola odorata is used as a source for scents in the perfume industry. Violet is known to have a 'flirty' scent as its fragrance comes and goes. Ionone is present in the flowers, which turns off the ability for humans to smell the fragrant compound for moments at a time.<ref>Ackerman, Diane. A natural history of the senses. New York: Vintage Books, 1991. Print.</ref>
- ITIS (Accessed December 2, 2002)
- The Oxford Companion to Food, by Alan Davidson, Oxford University Press. Template:ISBN
- Larousse Gastronomique, by Prosper Montagné (Ed.), Clarkson Potter, 2001. Template:ISBN
- Violaceae in Topwalks
- Viola charlestonensis type sheet from Louis-Marie herbarium (Laval University; Isotype, holotype is at University of California).
- Images of Japanese Viola Flavon's art gallery
- The American Violet Society
- Violacae images at botanische-spaziergaenge.at
- Template:Cite EB1911
- Template:Cite NSRW