Streptocarpus is a genus of herbaceous flowering plants in the family Gesneriaceae, closely related to the genus Saintpaulia. One common name is Cape Primrose, referring to the nativity of several species to South Africa and their superficial resemblance to the genus Primula. The genus is native to parts of Africa and Madagascar (with a few odd species in Asia that probably do not belong in the genus). The plants often grow on shaded rocky hillsides or cliffs. About 155 species of Streptocarpus are currently recognized, the first described being S. rexii. They are found growing on the ground, rock crevices, and almost anywhere the seed can germinate and grow. Some species such as S. dunnii are unifoliate with the plant producing no true leaves, only a single cotyledon that continues to grow throughout the life of the plant. The unifoliate species are monocarpic and die after producing seeds. Other species are perennial and come into flower during different parts of the year. Members of subgenus Streptocarpella are more typical caulescent herbs and are sometimes grown as bedding or hanging plants. The genus is defined by having a spirally twisted fruit (hence the name "streptocarpus"), although this character is also found in some other Old World genera of Gesneriaceae. Recent phylogenetic studies strongly suggest that although it does not have a twisted fruit the genus Saintpaulia has evolved from within subgenus Streptocarpella.
The leaves of some perennial (and particularly unifoliate) Streptocarpus are unusual because as winter approaches they slowly die back to an abscission line midway down the leaf. The tip of the leaf will gradually die back to this line. In most flowering plants an absiscion line forms at the base of the leaf.
A complete list of the species and their synonyms can be found at the Smithsonian Institution's World Checklist of Gesneriaceae.
The name Streptocarpus means twisted fruit.
- Selected species
A large number of hybrids and cultivars have been produced; S. rexii entered into many of the early hybrids but more recent cultivars often involve many different species. Recent cultivars have been bred to remain in bloom throughout the year. Over the past few years work has been done through hybridizing to bring other traits such as red flowers into modern hybrids. There are thousands of cultivars that are now grown as both houseplants and in the garden. The colors of the flowers range anywhere from red, white, yellow, blue, and everything in between including nearly black, except for a deep orange. Many flowers have markings in the "throat". More recently, breeders have been working to introduce floral fragrance to new hybrids from the relatively few species that have this trait.
Streptocarpus require bright indirect light and can be grown near a window or under fluorescent lighting. Streptocarpus are propagated by seeds, divisions, and leaf cuttings. The tiny seeds are dust-like and should be sown on the surface of the growing medium; they require light to germinate. The leaves can be cut into sections or down the middle to remove the central vein and then planted horizontally in light potting soil containing vermiculite and perlite. Members of subgenus Streptocarpella are easily propagated from stem cuttings.
Streptocarpus flowers are born on short and long peduncles (flower stems) that attach to the leaf stem. Several peduncles may be produced per leaf. New flowers come with new leaf growth.
Rosulate Streptocarpus form small clumps. As the plant grows it produces creeping stems that produce roots and will eventually separate to form other colonies. These creeping stems are called rhizomes.
There are several societies and organizations that exchange plant material for propagation in the form of leaf cuttings, plants and seeds as well as sharing their knowledge to help other growers. These societies are both large and small, and many of them are internet based groups. The Streptocarpus is a fairly new introduction as a houseplant and because there is not a wide information base on these plants new terminology is being introduced to describe them. For example, much of the communication between society and club members refer to Streptocarpus simply as "streps". In addition, some old terms associated with roses are now being adapted to Streptocarpus, namely "grandiflora" and "multiflora". Grandiflora refers to a cultivar that has relatively large flowers. Multiflora refers to a cultivar that has many flowers on a single peduncle, each flower usually being significantly smaller than those of the grandifloras.
The innovative efforts of modern hybridizers resulted in many exciting successes. One of these is the development of scented hybrids from crosses with S. vandeleurii. Another is the red flowers that are now found on many easy to raise cultivars, achieved by crossing a red unifoliate with modern hybrids.