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Genus of plants

Streptocarpus ("twisted fruit" from Greek στρεπτός (streptos) "twisted" and καρπός (carpos) "fruit") is an Afrotropical genus of flowering plants in the family Gesneriaceae. The genus is native to Afromontane biotopes from central, eastern and southern Africa, including Madagascar and the Comoro Islands. The flowers are five petalled, salverform tubes, almost orchid like in appearance, and hover or arch over the plant, while the pointed, elongate fruit is of a helical form similar to that of the "tusk" of a narwhal. In the wild, species can be found growing on shaded rocky hillsides or cliffs, on the ground, in rock crevices, and almost anywhere the seed can germinate and grow. For the home, there are now many hybrids of various colours and forms available. Although generally referred to simply as "Streptocarpus" or "Streps", the common name for subgenus Streptocarpus is Cape primrose, referring to the nativity of several species to South Africa and their superficial resemblance to the unrelated genus Primula. The common name for subgenus Streptocarpella is nodding violet. Streptocarpus sect. Saintpaulia ("African violet") is a separate section within Streptocarpus subgenus Streptocarpella. DNA studies have shown that, despite not having a twisted fruit, African violets evolved from within the Tanzanian Streptocarpus subgenus Streptocarpella. There are a few Asian species that have recently been removed from the genus, most notably Streptocarpus orientalis, now reclassified as Damrongia orientalis. Molecular systematics has shown conclusively that they are not true Streptocarpus.

There are two subgenera within Streptocarpus, namely subgenus Streptocarpus and subgenus Streptocarpella.

Within the Streptocarpus subgenus Streptocarpus, there are two main forms, the plurifoliates and the unifoliates. Streptocarpus with more than one leaf are called "plurifoliates", and there are two main types of these. First is the rosulate form, which is perennial. Rosulates are made up of a basal rosette of leaves. Flower stems sprout from the upper surfaces of the bases of these leaves. The most common Streptocarpus houseplant is of the rosulate type. The flowers of modern rosulate hybrids are generally three to several centimeters in diameter. The other plurifoliate type is essentially somewhere in between a rosulate and a unifoliate. In this group, two or three leaves grow in addition to the first leaf. The plurifoliates are perennial. Examples are Streptocarpus prolixus, and Streptocarpus polyanthus ssp polyanthus. The second form is the unifoliate, which only has one leaf. In the unifoliates group, one single leaf grows continuously from the base. Many unifoliates are also monocarpic, which means that they will flower once, set seed, then die. But they may take a few years to reach this stage. In other unifoliates, the original leaf may die, but one or two new leaves will sprout from it, and the plant continues to grow. and probably long tongued moths and bees. Although almost any small insect, animal, or breeze could potentially pollinate Streptocarpus. Streptocarpus flowers often have nectar guidelines that guide would be pollinators to the nectar (and anthers and stigmas). Self pollination is also common.

About 155 species of Streptocarpus are currently recognized, the first to be described being Streptocarpus rexii. A complete list of the species and their synonyms can be found at the Smithsonian's World Checklist of Gesneriaceae. The two main things to remember when growing Streptocarpus are that they do not like soil that is too wet, and they do not like it too hot. Soil: Use an ordinary commercial potting mix with 1/8 to 1/4 perlite mixed in. This makes sure the soil will retain some moisture but not get boggy. Always have adequate drainage holes at the bottom of the pot you are planting in. Temperature: They can be taken down to or less in winter for a rest. Light: Medium to bright indirect light is best. However, a bit of morning/late afternoon sun is more than okay. Even in dimmer light, they will flower but less floriferously. Water: Water only once the soil is almost dry. Some growers prefer to water only when the leaves have just started to wilt (or just before). They recover very well from dehydration, and this is one of the traits of the species. Make sure the pot has holes in the bottom to drain water, and never leave the pots sitting in a saucer of water. Feeding: Feed occasionally with a "fruit and flower" or general fertilizer. Seasons: Generally, Streptocarpus will flower from spring to autumn. In winter, they will stop flowering and may lose some leaves, which is normal. However, some varieties flower in winter. Pruning of leaves & flowers: You may slice off yellowing or browned leaves at the base these will be the older leaves naturally dying off. If there is a healthy leaf with some blemishing, you can successfully cut off only the blemished parts and trim the leaf to a normal shape. With regards to flowers, snip off individuals as they finish, then snip the whole stem off at the base once the last flower on that stem is spent. Cut flowers: Streptocarpus flowers also make excellent cut flowers, especially the long stemmed varieties. They last well. Pests and diseases: Streptocarpus are generally pest and disease free. However, the most common afflictions are aphids and mealybugs. These are easily treatable with commercial insecticides or cultural pest removal methods. Leaves and abscission: It is common for older leaves to die off occasionally, but especially in winter. They may be snipped off. New leaves will replace them. The leaves of some perennial, but usually unifoliate Streptocarpus, are unusual because, as winter approaches, they slowly die back to an abscission line midway down the leaf. The end portion of the leaf will gradually die back to this line. In most flowering plants, an abscission line forms at the base of the leaf, and the whole leaf will fall off (e. g. the leaves of deciduous trees like oak).

Hybridisation of Streptocarpus is conceptually very simple. The pollen of one plant (therefore the father) is placed onto the tip of the stigma of another plant (the mother). To prevent unwanted self pollination of the mother plant, carefully remove its anthers beforehand. To help prevent unwanted cross pollination, cover the newly fertilized stigma with a small plastic bag. If fertilization was successful, the seed pod will start to elongate within a few days. As the pod grows, it will start showing its namesake twisted form. Once the pod is mature, it will turn brown, dry off, and split open along the spiralled seams to release the seeds. Another method that is used to create hybrids is to use radiation or chemicals to alter the genes. For example, irradiation may be used (e. g. xrays, gamma rays) to induce mutations that may give rise to plants with new characteristics. Another example is the use of colchicine to induce polyploidy (multiplying number of chromosomes) in plants, also to introduce new traits. Over the years, numerous hybrids have been produced. S. rexii was used in many of the early hybrids, and its form is one that we most recognize in modern day hybrids. But more recent hybrids may contain the genes of other species or hybrids. When making a cross, hybridizers keep in mind which traits they wish to bring out or improve in the progeny. Much hybridizing work has been done to produce modern hybrids with an increased range of flower colours and forms, leaf variations, increased flowering periods, and more recently to introduce scent. Thanks to the work of hybridizers, Streptocarpus now come in a range of colours. These include reds, pinks, purples, blues, yellows, whites, and near blacks. The only colour that is so far not available is a true orange. Flowers now exist that are multicoloured, striped, spotted, veined, double, larger or smaller, and even fragrant and colour changing. There are also variegated leaf varieties, such as S. 'Canterbury Surprise'. Flower stems may be short or tall; leaves may be big or small; flowers may be full or dainty; and there may be one or many flowers per stem.