Saintpaulia, commonly known as African violet, is a genus of 6 species of herbaceous perennial flowering plants in the family Gesneriaceae, native to Tanzania and the adjacent southeastern Kenya in eastern tropical Africa, with a concentration of species in the Nguru mountains of Tanzania. The genus is most closely related to Streptocarpus, with recent phyllogenetic studies suggesting it has evolved directly from subgenus Streptocarpella. The common name was given due to a superficial resemblance to true violets (Viola, family Violaceae).
The genus is named after Baron Walter von Saint Paul-illaire (1860-1910), the district commissioner of Tanga province who discovered the plant in Tanganyika (now Tanzania) in Africa in 1892 and sent seeds back to his father, an amateur botanist in Germany. Two British plant enthusiasts, Sir John Kirk and Reverend W.E. Taylor, had earlier collected and submitted specimens to Royal Botanic Gardens, Kew in 1884 and 1887 respectively, but the quality of specimens was insufficient to permit scientific description at that time. The genus Saintpaulia, and original species S. ionantha, were scientifically described by J. C. Wendland in 1893.
Saintpaulias grow from 6-15 cm tall and can be anywhere from 6-30 cm wide. The leaves are rounded to oval, 2.5-8.5 cm long with a 2-10 cm petiole, finely hairy, and with a fleshy texture. The flowers are 2-3 cm diameter, with a five-lobed velvety corolla ("petals"), and grow in clusters of 3-10 or more on slender stalks (peduncles). Flower colour in the wild species can be violet, purple, pale blue, or white.
Several of the species and subspecies are endangered and many more are threatened, due to clearance of their native cloud forest habitat for agriculture.
Saintpaulias are widely cultivated as house plants. Until recently, only a few of these species have been used in breeding programs for the hybrids available in the market; most available as house plants are cultivars derived from Saintpaulia ionantha. A wider range of species is now being looked at as sources of genes to introduce into modern cultivars.
Over 2,000 cultivars have been selected for horticultural use. There are many different leaf and flower types found; cultivars are classified as Large, Standard, Trailing, Semi-mini, Mini, and Micro - with Micro being the smallest. There is a wide range in colour from white, pink, violet, dark red, yellow to even green, and the flowers may be either single (five petals) or double (more than five, with some or all of the stamens converted into extra petals). Flowers are not always a solid colour, but can also be found in the "fantasy" variety where the petals have coloured stripes. One interesting flower form found in the African Violet are known as a "wasp"; these flowers have the upper two flower petals independently fused forming a tube. There are also compound leaves on some, that are called "bustled".
Saintpaulias can be propagated by leaf cuttings (essential for propagating named cultivars) or seed (from which new cultivars are selected). African violets prefer a constant temperature between 20-25 °C (68-77 °F) with high humidity, and thrive best planted in well-drained humus or compost.
References : Wikipedia
Here is a collection of the hybrids i used to grow.