Wild Violet

Viola (plant)

Viola
Viola odorata (type species)
Scientific classification
Kingdom: Plantae
(unranked): Angiosperms
(unranked): Eudicots
(unranked): Rosids
Order: Malpighiales
Family: Violaceae
Genus: Viola
Species
List of Viola species

Viola is a genus of flowering plants in the violet family Violaceae, with around 400–500 species distributed around the world. Most species are found in the temperate Northern Hemisphere; however, viola species (commonly called violets, pansies or heartsease) are also found in widely divergent areas such as Hawaii, Australasia, and the Andes in South America.

Most Viola species are perennial plants, some are annual plants, and a few are small shrubs. A number of species are grown for their ornamental flowers in borders and rock gardens; the garden pansy in particular is an extensively used spring and autumn/winter bedding and pot plant. Viola and violetta are terms used by gardeners and generally in horticulture for neat, small-flowered hybrid plants intermediate in size between pansies and violets.

Description

Viola species 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.

Opened seed capsule, showing the seeds

A viola cultivar showing the large round flowers and the novel coloration that has been achieved through breeding.

The 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 Viola 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 flowers 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.[4] In some species the showy chasmogamous flowers are infertile (e.g.,Viola papilionacea).

After flowering, fruit capsules are produced that split open by way of three valves.On drying, the capsules may eject seeds with considerable force to distances of several meters.The nutlike seeds have straight embryos, flat cotyledons, and soft fleshy endosperm that is oily.  The seeds of some species have elaiosomes and are dispersed by ants.

Flower colours vary in the genus, ranging from violet, as their common name suggests, through various shades of blue, yellow, white, and cream, whilst some types are bicolored, often blue and yellow. Many cultivars and hybrids have been bred in a greater spectrum of colours. 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.

Selected species

White-and-purple form of Viola sororia

Bedding plants

The plants known to gardeners as “violas” are common bedding and pot plants world wide. In 2005 in the United States, violas (including pansies) were one of the top three bedding plant crops and 111 million dollars worth of flats of violas were produced for the bedding flower market.  Pansies and violas used for bedding are generally raised from seed, and 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.

Perennial cultivars

Weed control

Not all violets are desired, and wild violets are considered weeds in North American lawns by some people. 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.

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