Saintpaulia or African violets is one of the smaller genera in the Old World
Gesneriaceae. The twenty or so species of the genus are spread over an area of 70,000
square kilometers in Tanzania and Kenya (see map) and
individual species usually occur in very limited geographical areas. The plants grow as
rosettes or trailers and are often found on rocky hillsides, cliffs or rock outcrops
shaded by large trees. Most of the Saintpaulia species have been in cultivation for
many years, however, recent collections have suggested the possibility that new species,
varieties or hybrids may still be found in the wild. Only a limited number of the species
have been used in the hybridization programs that have produced the thousands of brightly
colored cultivars available today.
Taxonomy and Nomenclature
The genus Saintpaulia has generally stood as a distinct taxonomic unit after its description by Wendland from plants collected by Baron von St. Paul in 1892, and has had little confusion with other genera. Early workers, however, did sometimes place Saintpaulia near other genera based on morphological similarities. For example, Rodigas once synonymized the genus under Petrocosmea. The two genera are now separated by Petrocosmea lacking a well-defined floral disk and having more elongated anthers with two distinct chambers. The anthers of Saintpaulia have only one chamber and the flowers have a distinct disk. The fruit in Saintpaulia is a cylindric or subglobose capsule. The capsules may be short and stout or long and slender, but they are never twisted as in Boea or Streptocarpus (to get to the Streptocarpus genus page, click here, which this will take you out of this article -- to return, click your browser's back button).
Karl Fritsch monographed the Gesneriaceae in 1893 and classified Saintpaulia under the subfamily Cyrtandroideae in the tribe Ramondeae. Some other members of the tribe are Ramonda, Haberlea and Jancea. Another closely related genus is Platystemma which differs from Saintpaulia by having four fertile stamens instead of two. Recent DNA analysis suggests that Saintpaulia is not closely related to any of the genera that are similar to it in morphology, but is instead a close relative to subgenus Streptocarpella, of the genus Streptocarpus. Further DNA analysis should better place genus Saintpaulia with other genera in the Gesneriaceae.
Members of the genus Saintpaulia are characterized by peduncles that arise from the crown or from the leaf-axils along the stem. The peduncles bear 2-10 or more flowers in a cyme. The sepals, pedicels, and peduncles are usually covered with glandular hairs. The flowers of the Saintpaulia species are blue, blue-violet, bicolored or nearly white. The flowers are zygomorphic and 2-lipped with 5 rounded lobes. The upper lip is 2-lobed and smaller than the 3-lobed lower lip. The anthers are united at their tips and face each other. The pollen is not shed spontaneously. Sterile stamens or staminodes are represented by 2-3 papillae on the corolla-tube.
A ringlike orange or yellow disk surrounds the base of the superior ovary. The style and the stigma usually have the same color as the petals. The ovary is exserted slightly to the left or right of the center of the corolla. The stigma is small, terminal, papillose and often has a central depression.
African violets have two chief habits of growth, and are classified as either rosettes or trailers. Fritsch divided the three known species at that time into two sections based on this difference in growth forms. The rosulate species were known as the section Eusaintpaulia, while the trailing species were in the section Archisaintpaulia. This division into sections was later dropped by B.L. Burtt when more species become known because he thought dividing the plants into sections was artificial and did not represent true taxonomic relationships.
The reason behind the limited distribution for genus Saintpaulia is unclear, but may reflect some unusual feature in the ecology, seed dispersal mechanism, or evolutionary history of the genus. When the species are listed by their geographical locations, it can be seen that most of the species are found in the Usambara Mountains, particularly the East Usambaras which are home to 13 of the species and varieties. The remaining plants are found to the north (Kenya) or to the south (Nguru and Uluguru Mountains). See map.
The Saintpaulia species
The monographs of B.L. Burtt in 1958 and 1964 have been instrumental in the recognition of species and varieties in genus Saintpaulia. There are, however, several taxa that have not yet been described as species and a re-examination of the genus is currently being considered by some authorities. The species listed here follow Burtt's classification.
1. S. brevipilosa. This species was collected by W. R. Punter in 1959 in the Nguru Mountains at an elevation of 1000-1100 m and was described as a new species by B.L. Burtt in 1964. The leaves appear to be hairy only at the margins. Close examination with a lens will show that the upper surface has a very thick covering of short erect hairs. The flowers are small, usually 4-8 per stalk, and light purple with dark purple centers. The leaves are thin, round and light green with pale undersides. The plant normally grows in a rosette, but the petioles often twist so the leaves do not lay flat.
2. S. confusa. This species was described by B.L. Burtt in 1956 and is known from several locations and elevations in the East Usambaras Mountains. Populations of S. confusa have also been reported in the West Usambaras and Nguru Mountains.
The species name confusa comes from the "confusion'' about the taxonomic history of the species. S. confusa materials have been identified as S. ionantha, S. kewensis and S. diplotricha. S. confusa appears to be the taxon collected in the East Usambaras Mountains in 1891 by Baron von St. Paul and was undoubtedly used in the development of today's cultivars.
There are at least two distinct clones of S. confusa available in cultivation. One clone has smooth shiny light green triangular shaped leaves. The other clone grows larger and has more hairs on the leaves which are more ovate in shape. The flowers of S. confusa are medium size, two to six per stalk and blue-violet or deep purple in color. The plant frequently forms multiple crowns by suckering, but it is not a true trailer.
3. S. difficilis. This species was first collected by W.R. Punter in 1939 in the East Usambaras Mountains and was described as a species by B.L. Burtt in 1958. It has been collected several times from the head waters of the Sigi River at elevations of 900-1050 m.
The flowers of S. difficilis are medium sized, 5-7 per stalk and dark blue. The leaves are longer than wide, thin, pointed and have impressed veins on the upper surface. The young leaves are sharply serrated, but become almost smooth as the leaf ages. The leaves are frequently chartreuse green in color with pale undersides. This plant usually grows with a single crown.
Variation between populations is known for this species. Several clones are known in cultivation, but most have not been widely distributed.
4. S. diplotricha. This species was first collected in the East Usambara Mountains in Tanzania in 1895 at an elevation of 1000 m, but was described by Burtt in 1947 from a cultivated plant that had been known as S. kewensis.
S. diplotricha is characterized by having two types of leaf hairs, one that is long and spreading and the second that is very short and erect. The leaves are lightly serrated, thick, and dark green with a reddish purple reverse. The plants are upright rosettes with 5-7 pale lilac blossoms per stalk. There are several clones of S. diplotricha, which are described below in the "Other Saintpaulia taxa".
5. S. goetzeana. This species was collected by W. Goetze in 1898 from the Uluguru Mountains in Tanzania and was described as a species by Engler in 1900. Although this species is one of the oldest Saintpaulia species known it is very difficult to grow and rarely flowers in collections. This species was collected at elevations of 1300-2000 m as a creeping herb on mossy rock surfaces in deep shade in upland rainforests. These are not conditions that can be reproduced easily in cultivation.
The flowers are reported to be small, 1-2 per stalk and have lilac upper lobes and white lower lobes. The leaves are small, round and dark green with smooth edges. The growth habit is a creeping trailer with two clear leaves per node.
6. S. grandifolia. This species was collected by W.R. Punter in the West Usambara Mountains was described by B.L. Burtt in 1958. Some collections may incorrectly give the name for this plant as S. grandiflora.
S. grandifolia has small dark blue flowers with up to 20 or more flowers per stalk. Frequently two bloom stalks per leaf axil are formed. The leaves are large and can measure 8 cm long by 10 cm wide. The leaf blades are very thin, and light green with long pliable petioles. The leaves are serrated, are somewhat quilted in texture, and have a pale green reverse. The growth form is a single crown and specimens can easily reach 30-40 cm in diameter.
7. S. grotei. This species was collected by H. Grote in the East Usambaras Mountains near Amani at an elevation of 1080 m and was described by Engler in 1921. This species is a fine example of the trailing growth form in African violet and several clones are known in cultivation. This species has 1-2 blue to light blue flowers per stalk. The photo has two flowers, one larger and darker than the other. In this case, the smaller and lighter flower is atypical for this particular clone, but within the range of the species.
The petioles range from wiry and green to dark brown in color. They terminate in flat, rounded serrated leaves which vary in size from 2-6 cm in width. The leaves are thin and may be deeply toothed. The leaves range from pale green to dark green. The underside of the leaves is usually pale green, but the veins may show the brownish coloration of the petioles. Some clones have a red reverse on the leaves. The plants are large trailers and may form roots at the leaf nodes.
S. grotei was the species that was first used in developing the trailer African violet cultivars available today. The growth form has been improved and selective breeding has increased the number of flowers and the range of flower colors.
8. S. inconspicua. This species was first recorded in 1934 from the Uluguru Mountains in Tanzania by E.M. Bruce. It was found at an elevation of 1370 m on moist soil in the forest. It was described by B.L. Burtt in 1958 from herbarium material. Originally, the herbarium specimens were marked as Didymocarpus, but the plant is now considered by be a true Saintpaulia.
This species is a miniature and grows to a size of no more than 15 cm. It is reported to have small blue-spotted white blossoms and a very loose upright trailer growth habit. The leaves are 2-3 cm wide and 4-5 cm long. The leaves are nearly hairless, except on the leaf margins. This species is not currently in cultivation (if it ever was). Its status in the wild is uncertain and it may be extinct.
9. S. intermedia. This species was collected by W.R. Punter in the East Usambara Mountains, Kigongoi, Tanzania and was described by B.L. Burtt in 1958. The flowers are medium blue and clustered 5-6 to a stalk. The leaves are almost round, toothed, and covered with dense short hairs. The leaves are dark green on top with red reverses and green veins. The plants are intermediate between rosette and trailing, becoming more trailing with maturity.
10. S. ionantha. This species is the one that the world has generally come to know as "The African violet'' and its descendants are the basis of the African violet commercial sales. The plant was described as a new species by H. Wendland in 1893. Plants that have been synonymized with this species include Petrocosmea ionantha and Saintpaulia kewensis. The species has been collected in several places in Tanzania, but it is usually found near sea level or at other lowland sites.
The flowers of S. ionantha are medium blue and number 4-8 per stalk. The leaves are serrated and are dark green with red reverse. The plants are usually grown as a single rosette, but do show some tendency to sucker. This species can be a large grower and may be up to 45 cm in diameter. A nearly white clone is reported (see "Other Saintpaulia Taxa" below).
11. S. magungensis. B.L. Burtt recognized three varieties for S. magungensis. The original species is S. magungensis var. magungensis. This plant was described by E. Roberts in 1950. The plant was collected in the East Usambaras Mountains near Magunga, Tanzania. A different population of the species, originally named as S. amaniensis by Roberts, was synonymized into S. magungensis by B.L. Burtt in 1958.
S. magungensis var. magungensis has flowers that are blue-violet with darker centers and are usually 2-4 flowers per stalk. The leaves are serrated, round in shape and are approximately 3-7 cm in diameter. The leaves are medium green with near white reverse and are often cupped downwards. This plant has a trailer growth form, but the internode distances are relatively short. A variety of the species, S. magungensis var. minima, was described by B.L. Burtt in 1964. This plant was collected by W.R. Punter from the East Usambaras Mountains. This variety appears to be a small version of the S. magungensis species. It has very tiny light purple flowers that are borne 1-2 per flower stalk. The leaves are smaller and thinner than the parent species, are lightly serrated, and have a pale green reverse. This plant has a trailer growth form and seems to require a higher humidity than some of the other species. This variety was an important source of genetic material for developing semi-miniature and miniature trailers.
The variety S. magungensis var. occidentalis was collected by W.R. Punter in 1959 in the West Usambaras Mountains, near Bagai, Tanzania, and was described as a variety by B.L. Burtt in 1964. This variety is a reluctant bloomer and has 2-5 violet-blue flowers per stalk. The leaves are medium green to dark green, shiny, ovate and have a red reverse. The leaves may tend to spoon or fold in some clones. This variety is a more upright or semibush style trailer than the other varieties.
12. S. nitida. This species was collected in 1953 by Drummond and Hemsley at an elevation of 1000 m in the Nguru Mountains near Turianai, Tanzania, and was described as a species by B.L. Burtt in 1958.The flowers of this species are small, dark purple and 5-7 per stalk. The leaves are nearly round and about 4-5 cm in diameter. The chief character for recognition for this species is its shiny and smooth leaves. The leaf hairs are very inconspicuous and the leaves appear to be coated in wax. The leaves are medium green on top and reddish underneath. The plants can be grown as single crowns or as multiple crown trailers.
13. S. orbicularis. B.L. Burtt recognized two varieties for this species. They are very similar to each other and differ only in the depth of flower color.
S. orbicularis var. orbicularis is the original species and was described by B.L. Burtt in 1947. It was discovered by A. Peter in 1916 in the West Usambara Mountains at an elevation of 1200 m. The flowers are small, 5-8 per stalk, and are pale blue to lilac with darker centers. The plants tend to produce two flower stalks per leaf axis, giving a good show of the tiny flowers. The leaves are round, thin, shiny and medium green with pale undersides. The leaf blade is usually held at a sharp angle to the petiole allowing the leaves to be raised above the growing point like an umbrella. The plant may be grown as a single or multiple crown specimen.
The second variety, S. orbicularis var. purpurea was described by B.L. Burtt in 1964. The plant was collected by W.R. Punter in 1958 in the West Usambaras Mountains. This variety is very similar to the parent species except that the flowers are dark purple in color. The leaves and petioles of this variety also tend to show more red or purple coloration.
14. S. pendula. B.L. Burtt recognized two varieties for this species. The original species is known as S. pendula var. pendula. It was collected by W.R. Punter from the East Usambara Mountains, Mt. Mtai, Tanzania, and was described by B.L. Burtt in 1958. Several clones of this species are known in cultivation. The flowers of this species are usually produced only 1 per stalk, which is a unique feature for the genus Saintpaulia. The flowers are somewhat cupped and do not extend much above the foliage. Flower color is light to medium blue, but the flowers often show a paler blue centers especially on the lower three petals. The leaves are yellowish green, slightly toothed, and are longer than wide. The leaves are very thick and extremely hairy. This plant has a modest creeping trailer growth habit depending on the clone, with relatively short internodes
S. pendula var. kizarae was collected by W.R. Punter in 1958 from the East Usambaras Mountains near Kizara, Tanzania, and was given varietal status by B.L. Burtt in 1964. The flowers of this variety are medium blue-violet and are found 2-4 per stalk. The flowers are larger than in the parent species and are held above the foliage better. The leaves are longer than wide and thinner than the parent species. The leaves are hairy, medium green and slightly toothed. The growth habit is trailing, but the plants stay upright and compact forming multiple crown specimens.
15. S. pusilla. This species is one of the oldest known species, having been collected by W. Goetze in 1898, but is not currently known in modern collections. It has been reported at a number of locations from the Uluguru Mountains in Tanzania, and was described as a new species by Engler in 1900. This species is a high mountain species, growing at elevations of 1200-1800 m.
This plant is a true miniature. It is described as having tiny flowers with mauve top petals and white lower petals. The leaves are tiny, triangular in shape, and have purple red reverses. The plant grows as a single crown.
16. S. rupicola. This species was collected by W.R. Punter in 1958 and was described by B.L. Burtt in 1964. This species is one of the few that is found in Kenya and several clones are known in cultivation.
The flowers are medium sized and medium to light blue. They are usually 4-6 per stalk and are held well above the foliage. The leaves are an elongated heart in shape, shiny, and medium to light green. They have light green undersides and brownish or green petioles. The leaf margins are shallowly serrated and may appear smooth at maturity. The plants may have a single crown that grows slanted rather than upright, but they frequently produce suckers, resulting in multiple crown specimens.
17. S. shumensis. This species was collected by P.J. Greenway in 1947 from the West Usambaras Mountains near Shume, Tanzania, and was described as a species by B.L. Burtt in 1955. This species is from high elevations, growing from 1900-1950 m. A population of this species has also been reported on Nilo Peak in the East Usambara Mountains and in the Nguru Mountains. If the reports are accurate, this species would then be one of the few to occur in several different mountain locations. Several clones are known in cultivation.
The flowers of S. shumensis are usually small and pale blue to almost white. The center of flower may have a darker dot of blue. They are usually found 1-3 per stalk and are very short lived. The flowers frequently self-pollinate and produce narrow elongated capsules. The leaves are small, round and bright green and have a "strawberry pebbling'' on the surface where a single long hair originates. The plants are miniature, growing 6-8 cm in diameter.
18. S. teitensis. This species was first collected in the Teita Hills, Kenya in 1938 and was described from herbarium material by B.L. Burtt in 1958. The flowers of this species are medium sized, dark blue and are produced 4-8 per stalk. The leaves are thick and leathery in texture. The leaves are dark green, shiny and may have a red reverse. The veins are often raised rather than depressed and the leaf margins are almost smooth. The plants are upright rosette growers.
19. S. tongwensis. This species was collected by P.J. Greenway in 1940 from the Tongwe Mountain in the East Usambaras Mountains at an elevation of 600 m. It was described as a species by B.L. Burtt in 1947 and several clones are known in cultivation. The flowers of S. tongwensis are medium size and light blue in color. The flowers can be produced in large quantities with 8-14 flowers per bloom stalk. The leaves are very heavy, hairy, longer than wide, and pointed. The leaves usually have a red reverse and may have a paler yellow-green midrib. In some growing conditions the veins show an almost variegated leaf appearance because of their pale yellow coloring. The plants grow as a single crown and rarely sucker. The plants may reach a size of 25-30 cm in diameter.
20. S. velutina. This beautiful, but temperamental species was collected by A. Peter in 1916 in the West Usambara Mountains, near Balangai, Tanzania, at an elevation of 900 m. It was described as a species by B.L. Burtt in 1958. The flowers are small, medium violet and 6-12 per flower stalk and may develop white edges. The leaves are heart-shaped, deeply scalloped, and have a velvety texture due to the long hairs that protrude from the surface. The leaves are dark green on top and normally have a rich red reverse. The older leaves tend to cup downward around the stem. The plant usually grows as a single crown.
Other Saintpaulia Taxa
In addition to the plants described by B.L. Burtt, there are a number of other taxa that are known for genus Saintpaulia. Some of these are forms of a species and have been recognized by the African Violet Society of America (AVSA) through their inclusion on the Master Variety List. Others are potential new species or varieties that have yet to be recognized.
The AVSA recognizes three forms of S. diplotricha. Form Punter #0 is an upright rosette plant with pale lilac blossoms with bright yellow stamens. The flowers are relatively large and have rounded petal lobes. There are 5-7 blooms per stalk. The leaves are lightly serrated, thick, and dark green with a reddish purple reverse. The plants rarely sucker and may grow from 15-30 cm (6-12 in) in diameter.
S. diplotricha form Punter #6 also has 5-7 pale lilac blossoms per stalk. This form also grows as a upright rosette and is somewhat smaller in size than Punter #0. The leaves are smaller, rounder in shape and have more of a tendency to spoon. The leaf margins are almost entire. Punter #6 is very similar to Punter #0 with the main differences being in the smaller plant size and in the rounder leaf shape.
S. diplotricha form Punter #7 has blue-gray blossoms which are smaller and have more pointed lobes than the other forms. The leaves are pointed, heart-shaped, with a pale red reverse. The leaves are more coarsely serrated than in the other forms and show a tendency to cup downward. The leaves are also more quilted or tailored in texture.
The AVSA recognizes two forms of S. grandifolia. Form #237 is the original species as described by B.L. Burtt. Form #299 has slightly larger blooms that are a darker shade of purple than in form #237. The leaves are more deeply crinkled and quilted.
Two forms of S. grotei are available commercially, but are not recognized in the Master Variety List of the AVSA. The first is called S. grotei 'Amazon' and is a tetraploid version of the species. This plant is larger than the species and often forms 3-5 flowers per stalk. The leaves are also more scalloped and the veining is more pronounced. The second form, S. grotei 'sport', differs from the parent species in that it is a chimera that has white flowers with a blue center stripe. This plant is also reported to have shorter internodes and the flowers are frequently male sterile with no pollen.
There have been a number of different color forms reported for S. ionantha. R.H. Beddome (1908) distinguished a pale lilac, a very dark blue, white violet-tinted, and a reddish flowered plant with longer leaves. Much of the history of origin of these variants has been lost and the accuracy of the reports is somewhat questionable.
A more recent case in the color variation in S. ionantha is illustrated by the plant called "Saintpaulia ionantha (white)". This plant has not been described as a new species nor has it yet been recognized as a new form by the AVSA. This plant has white flowers with only the palest trace of blue color. The leaves are medium green with pale green undersides.
A tetraploid version of S. ionantha, S. ionantha 'Amazon' has been reported. This plant varied from the diploid by having larger leaves and flowers. This plant has not been seen for some years, but may still be available.
Two additional forms are known for S. velutina. The first is a tetraploid known as S. velutina 'Amazon'. This plant is larger than the diploid version and has dark violet flowers. The hairs on the leaves are even larger than on the diploid plant, making this plant look like it has fur. The blooms are also larger and last longer.
The second form is a mutant and is sometimes found on plant lists as S. velutina 'Light'. It was discovered as a sport of a leaf cutting of S. velutina by Diane Richardson of Baltimore, Maryland in 1991. This plant is a miniature version of the species and has very pale lilac or almost white flowers. The leaves are less scalloped, more rounded, and the size of the hairs has been reduced.
The plant known as 'House of Amani' is not currently recognized as a separate species although it is listed with the AVSA Master Variety List. The origin of the plant is unclear, but it may have been first offered by the Amani Plant House in Tanzania and the name developed from this origin.
This plant has blue-violet flowers that are produced 3-5 per stalk. The flowers are held up above the foliage, but are not especially long lived. The leaves are dark green, slightly toothed, and pointed. When grown in strong light, the leaves may develop a slight red reverse, but the plant usually shows a green reverse. The veins often develop dark coloration, especially when the plant is grown under high light. The plants grow as a single crown rosette and mature specimens can reach 25 cm in diameter. 'House of Amani' is very similar to the species S. ionantha and it is likely that 'House of Amani' is a variety of that species.
The plant known as 'Saintpaulia Robertson' is the newest taxa to become available in the United States. This plant was collected by Ann Robertson and Quentin Luke in 1988 at an elevation of 100 m in the Kilifi area of Kenya. The flowers of 'Saintpaulia Robertson' are medium blue and large compared to many of the other species. The flowers are slightly cupped and are found 4-6 per stalk. The leaves are thick, much longer than wide, and pointed. The leaves are medium green with a pale green reverse. The petioles of mature leaves are often strongly arched, bending the leaf blades downward and giving the plant an interesting "fountain" appearance.
The plant known as 'Sigi Falls' has not been recognized as a separate species, but it is listed on the AVSA Master Variety List. The plant was collected from the sides of a waterfall on the Sigi River in the coastal area of Tanzania. The plant has medium blue flowers that are produced 2-4 per stalk. The leaves are large, and almost succulent in thickness. The leaves are hairy, elongated and pointed. The leaves have a red reverse and often have a yellow-green midrib area. The plants have relatively short internodes, making them grow as a weak trailer and forming multiple crowns.
In 1985, the Usambara Rain Forest Research Project visited an isolated mountain block south of the West Usambaras called Mafi Hill. At 1200 m, a plant was collected and provisionally given the name S. mafiensis. Although supposedly confirmed by B.L. Burtt, nothing further has been reported and the plant has not been published as a new species. A specimen labeled as S. mafiensis was deposited at the herbarium of the Uppsala Botanical Gardens of Uppsala, Sweden.
The Mather and Uppsala Collections
The Mather collection is named after the person who gathered the plants, the late Mrs. Silva Mather of Nairobi, Kenya. The Saintpaulia plants in the Mather collection were either gathered personally by Mrs. Mather or were obtained from other collectors and growers in Africa.
The Uppsala Botanical Garden collection is from Uppsala University, Sweden, and contains Saintpaulia material collected during 1986-87 during the Usambara Rain Forest Research Project. The Uppsala collection also contains material collected in 1983-84 and a few more recent specimens were added in the early 1990's.
The Mather collection has already produced two plants of interest, 'Saintpaulia Robertson' and 'Saintpaulia white ionantha'. While neither has been recognized as a new species, there has been considerable interest in both plants since their commercial introduction in 1993. Other plants under study from the Mather collection include an unknown trailing species with leathery leaves with red backing (clone of S. magungensis var. magungensis?); a plant collected by Brother Paddy MacNamara that resembles S. shumensis, but grows three times larger; a trailing plant labeled as S. grandifolia #7; and a new clone of S. magungensis var. occidentalis. Interesting plants from the Uppsala collection includes a plant labeled as S. magungensis var. minima which appears to be a new clone of S. pendula var. pendula. Another Uppsala plant, S. grotei Protzen, is a new clone of this species with large light green leaves and pale blue flowers.
Genetic Studies of the Saintpaulia species
Many of the species of genus Saintpaulia have been examined and studied for chromosome number. In all species and varieties examined to date, the chromosome number has been N=15. A number of hybridization attempts have been made between many of species. The results indicate that there are little if any genetic barriers between the species as most species can be freely crossed with any other and produce fertile offspring.
There are two species which do not seem to cross freely with the others, S. nitida and S. shumensis. While these two species are interfertile with each other, difficulty has been reported in obtaining hybrids between them and other species.
All attempts to hybridize Saintpaulia species with other genera have failed.
Ecology of Saintpaulia
All of the Saintpaulia species, except perhaps S. rupicola, require moist and deeply shaded conditions in their natural habitats. They often grow on steep rocks or in gullies, along the north side of shaded streams, or as an undergrowth in dense submontane or montane rain forests. In most cases, the plants grow in the shallow soils covering rocks or in pockets of humus caught in rock outcrops. The genus can be said to be lithophytic, that is, they grow preferably on rocks, particularly on steep surfaces. The growth habit resembles in many respects that of rain forest epiphytes, which often share the rock substrate with the Saintpaulia species. The majority of the species grow on acidic, metamorphic gneiss or granitic rocks with pH down to 4.8. A few species grow on limestone rocks where the humus has been measured to a pH of 7.3.
The elevation of a species' habitat should be considered when growing them in cultivation. Species such as S. diplotricha, S. intermedia, S. ionantha, and S. rupicola are from low elevations. These species require warm growing conditions and do well in warmer growing areas such as the top shelves of plant stands. Other species such as S. goetzeana and S. velutina are from high elevations and grow best under cooler growing conditions such as sills of north windows or the lower shelves of plant stands. The blooming of S. goetzeana, S. teitensis, and S. magungensis var. occidentalis requires very cool night temperatures, a condition that reflects their mountain origins.
Conservation of genus Saintpaulia
The species of genus Saintpaulia are in trouble.
Especially in the Teita Hills, the Usambara and Uluguru Mountains, there is a high
pressure on the remaining rain forest patches. When the forest is cleared for logging,
cash crops or local cultivation, the habitats dry out and the Saintpaulia
populations slowly dry out as well. These plants need the trees for shade protection from
the hot tropical sun. The increased light on the forest floor after the trees have been
removed may also permit the growth of other plant species which compete with the Saintpaulia
species for water and space.