Streptocarpus

''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''.Bellstedt, D. U., ''Streptocarpus'' Genus Overview

Description

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

Subgenus ''Streptocarpus''

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.

This subgenus (comprising plurifoliates and unifoliates) is unique in that, in winter, they can form abscission lines part way down the leaf (see photo gallery below). The leaf then dies back to this point, whilst the proximal part of the leaf stays alive and healthy. In unifoliate species, the remaining healthy portion of that leaf will start to grow again from the base.

Subgenus ''Streptocarpella''

Members of the ''Streptocarpus'' subgenus ''Streptocarpella'' are very different in form to those mentioned above.

The flowers and seed pods are similar, but the leaves and stems are caulescent (have stems). ''Streptocarpellas'' are generally clump-forming or trailing plants. Their flowers are only about 2.5-3.5 cm in diameter, and their colour range seems to be limited to mid-purples, pale pinks, and white.

''Streptocarpella'' leaves can be decussate in arrangement (each pair of leaves at a node is at 90 degrees to the ones preceding or following it), or ternate (whorls of 3 leaves at each node). Some specimens may exhibit both on the same plant. Streptocarpella are grown as houseplants, hanging plants, and sometimes as bedding plants.

These two ''Streptocarpus'' subgenera do not interbreed.

For information on ''Streptocarpus'' subgenus ''Streptocarpella'' section ''Saintpaulia'', see ''Streptocarpus'' sect. ''Saintpaulia''.

Flower anatomy

''Streptocarpus'' flowers are five-lobed, salverform, zygomorphic tubes. The diagram at the right shows a labelled drawing of a vertical cross-section along the length of a ''Streptocarpus'' flower.

It is important to note that the two anthers (each arising from one filament on each side of the flower), are loosely joined together. As the anthers mature, they open slightly and act like a pepper shaker, which means that not all the pollen is released at once.

''Streptocarpus'' flowers have evolved to be pollinated by birds, long-tongued flies, butterflies 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.

Species

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.

A list of selected species from representative locales follows:

* '' S. andohahelensis'' Humbert (Madagascar)
* '' S. candidus'' Hilliard - scented (South Africa, Natal)
* '' S. caulescens'' Vatke (Kenya, Tanzania)
* '' S. confusus'' Hilliard (South Africa)
* '' S. cooperi'' C.B.Clarke (South Africa)
* '' S. cyaneus'' S. Moore (South Africa, Transvaal)
* '' S. denticulatus'' (South Africa)
* '' S. dolomiticus'' - in the process of being described (origin unknown)
* '' S. dunnii'' Hook. f. (South Africa)
* '' S. elongatus'' Engl. (Cameroon, San Thomé Island, Sudan)
* '' S. eylsii'' S.Moore - scented (Zimbabwe, Malawi, Mozambique, Zambia)
* '' S. fanniniae'' Harv. Ex C. B. Cl. - scented (South Africa)
* '' S. fenestra-dei'' Weigend & T.J.Edwards (South Africa, Transvaal)
* '' S. formosus'' (Hilliard & B.L.Burtt) T.J.Edwards (South Africa)
* '' S. gardenii'' Hook. (South Africa, Natal)
* '' S. glandulosissimus'' Engl. (Burundi, Congo, Kenya, Rwanda, Tanzania, Uganda)
* '' S. insularis'' Hutch. & Dalziel (West Africa: Fernando Po Island)
* '' S. kentaniensis'' L.L.Britten & Story (Congo)
* '' S. liliputana'' D.U.Bellstedt & T.J.Edwards (Pondoland in Eastern Cape, South Africa)
* '' S. meyeri'' B.L. Burtt (South Africa)
* '' S. milanjianus'' Hilliard & B.L.Burtt (Malawi)
* '' S. modestus'' L.L.Britten (South Africa)
* '' S. pentherianus'' (South Africa)
* '' S. polyanthus'' Hook. (South Africa)
* '' S. pusillus'' Harv. ex C.B.Clarke (South Africa)
* '' S. revivescens'' Humbert ex B.L.Burtt (Madagascar)
* '' S. rexii'' (Bowie ex Hook.) Lindl. (South Africa)
* '' S. rhodesianus'' S.Moore (Angola, Katanga, Zambia)
* '' S. saxorum'' Engl. (Kenya, Tanzania)
* '' S. trabeculatus'' Hilliard (South Africa)
* '' S. vandeleurii'' Baker f. & S.Moore - scented (South Africa)
* '' S. variabilis'' Humbert (Madagascar, Comoro Islands, Anjouan Island)
* '' S. wilmsii'' Engl. (South Africa)
* '' S. zimmermannii'' Engl. (Tanzania)

Cultivation

Each grower will have their own preferences for cultivation. The details given below are a tested general guide, but ''Streptocarpus'' will do quite well on either side of these optimums.

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 floriferous

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