The Darwinian definition of a species i.e. that it will only give rise to infertile offspring if crossed with another species falls flat on its back in the case of the genus Streptocarpus. Within subgenus Streptocarpusthere are very little barriers with regard to hybridization. As a result the subgenus Streptocarpus is a hybridizer’s paradise and many crosses have been made since Streptocarpus rexii was first introduced. These are well documented in Hilliard and Burtt (1). A number of notable events with regard to hybridization should be mentioned. The introduction of Streptocarpus dunni in 1882 resulted in the production of red-flowered hybrids which still are the center of attention if one is to gauge by the images shown on this website. The development of a tetraploid called Merton’s Giant resulted in large hybrids. By crossing Merton’s Giant with Streptocarpus johannis, the hybrid “Constant Nymph” was developed in 1947. This hybrid formed the base for many modern hybrids.
Another notable event was the development of the deep purple flowered Streptocarpus hybrids by the John Innes Institute. These were the result of mutations induced by radiation. In recent times the development of double flowered Streptocarpus hybrids have caused quite a stir and are now readily available. Certain species have again been crossed into the modern hybrids in an attempt to inprove certain characters. Streptocarpus kentaniensis which flowers in winter has been used to extend the flowering period of hybrids. Streptocarpus johannis has also again been used to develop the very floriforous hybrids such as “Gloria” and “Seven Stars”. In my opinion, although I am not a hybridizer, some of the S. johannis variants hold considerable potential for hybridizers. Attempts have also been made to breed smallStreptocarpus similar in size to African Violets and in this regard the potential of species such as S. pusillus, S. rimicola and S. occultus have hardly been exploited.