Saintpaulia


Streptocarpus sect. Saintpaulia is a section within Streptocarpus subgenus Streptocarpella consisting of about ten species of herbaceous perennial flowering plants in the family Gesneriaceae, native to Tanzania and adjacent southeastern Kenya in eastern tropical Africa. The section was previously treated as a separate genus, but molecular phylogenetic studies showed that it was nested within the genus Streptocarpus.
Species and cultivars are commonly called African violets or saintpaulias. They are commonly used as indoor houseplants, but can also be kept as outdoor plants in certain climates.
Several of the species and subspecies of the section are endangered, and many more are threatened, as their native cloud forest habitats are cleared for agriculture. The conservation status of Streptocarpus ionanthus has been classed as near-threatened.

Description

Saintpaulias, which grow from 6–15 cm tall, 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 have a fleshy texture. The flowers are 2–3 cm in diameter, with a five-lobed velvety corolla, and grow in clusters of 3–10 or more on slender stalks called peduncles. Wild species can have violet, purple, pale blue, or white flowers.
The plants get their common name "African violet" from their superficial resemblance to true violets.

Taxonomy

The section was initially regarded as a separate genus. Baron Walter von Saint Paul-Illaire was the district commissioner of Tanga province when he discovered the plant in Tanganyika in Africa in 1892 and sent seeds back to his father, an amateur botanist in Germany. The genus was named for Saint Paul-Illaire and his father. Two British plant enthusiasts, Sir John Kirk and the Reverend W.E. Taylor, had earlier collected and submitted specimens to the 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 H. Wendland in 1893.
Revisions of the genus by B.L. Burtt expanded the genus to approximately 20 species. Following studies which showed most of the species to be very poorly differentiated, both genetically and morphologically, the number of species was reduced to six in a 2006 treatment, with the majority of former species reduced to subspecies under S. ionantha. In 2009, 9 species, 8 subspecies, and 2 varieties were recognized.
A molecular phylogenetic study in 2015 confirmed previous studies showing that species placed in Saintpaulia were deeply embedded within the genus Streptocarpus, supporting the transfer of all Saintpaulia species to Streptocarpus in 2012. Former Saintpaulia species did form a monophyletic group, and were placed in section Saintpaulia of Streptocarpus subgenus Streptocarpella.

Species

All the species previously placed in the genus Saintpaulia are now placed in Streptocarpus in section Saintpaulia. Ten species are recognized, as of 2020.
Formerly recognized Saintpaulia species and infraspecies are listed below with their accepted name in Streptocarpus.
Saintpaulias are native to eastern tropical Africa. There is a concentration of species in the Nguru mountains of Tanzania.

Cultivation

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 Streptocarpus ionanthus. A wider range of species is now being looked at as sources of genes to introduce into modern cultivars.
The African Violet Society of America is the International Cultivar Registration Authority for the section and its cultivars.

Sizes

Plants can be classified as one of several sizes based on its above-ground diameter. Although the size per category is not set in stone, these are a general guideline.
Saintpaulias are highly sensitive to temperature changes, especially rapid leaf cooling. Spilling cold water on African violet leaves causes discoloration. This is thought to be because rapid leaf cooling causes cell vacuole collapse in the palisade mesophyll cells.

Propagation

African violets are commonly propagated asexually. Plants can be divided into smaller daughter plants or even grown from leaf cuttings.
Growing African violets from seed is rare and most commercially available plants are produced from cuttings and tissue culture.

Flowering

The African violet is a day-neutral plant regarding flower development.

In culture

African violets have long been associated with mothers and motherhood. For this reason they have been a traditional gift to mothers in many cultures around the world. African violets are also associated with Easter and Valentine's Day.