Viola is one of 22 genera of plants in the violet family Violaceae. There are about 500 different species throughout the world. Many are found in the Northern Hemisphere where the climate is temperate; however, there are some found in other areas such as Australasia, the Andes in South America and in Hawaii.
Most of the flowering species in this family are known as violets, pansies or violas. The species Viola have heart-shaped, scalloped leaves, although there are some that have palmate or various other shaped leaves. The flowers have five sepals and five petals. One of the petals is lower than the others and has a scoop shape. The anthers of the stamens are gathered around the base of the pistil. The pistil is solitary and the style and the stigma are shaped like a club.
Many of Viola are herbaceous and many lack any obvious stem. On this group the flowers and the leaves appear to grow directly from the ground. Others in the species have short stems. The leaves and the flowers grow from the axis of the leaves. The leaves are simple leaves which are arranged alternately.
These flowers usually bloom in the spring. Most are self-pollinated in the summer and autumn but in the spring the blooms are arranged in such a way that they are easily pollinated by insects. In some, such as the Viola papilionacea, the flowers are infertile.
Fruit is produced after flowering. These capsules break open at three valves. When they are dried they may send the seeds with such force that they can travel up to ten feet. The seeds are like nuts and have straight embryos, soft flesh endosperm and flat cotyledons. Some species have seeds that are spread by ants.
The colors of these flowers can range from purple to blue, yellow, white and cream. Some of them can be bi-colored. They can also be hybridized to bloom in a greater variety of colors.
Viola flowers may appear to have no aroma, however this is due to a ketone compound called ionone. This will desensitize receptors in the nose so any other scent cannot be smelled until recovery of the nerves.
This genus includes many plants that may be known by their common names: field pansy (Viola arvensis); yellow wood violet, or twoflower violet (Viola biflora); heath dog violet (Viola canina) Corsican pansy (Viola Corsica); hairy violet (Viola Hirta) along with many others. The African violet and the dogtooth violet are not part the Viola.
There are many viola and violettas which are perennials. Most of these have to be propagated from cuttings. Violettas do not have ray markings on their petals, unlike violas which do.
