Streptocarpus primulifolius, Cape Primrose, Nodding Bells
The genus Streptocarpus is one of the better known of our South African plants that belong to the African Violet and Gloxinia family. They have been in cultivation for centuries in hothouses in the northern hemisphere. This blue to violet, summer-flowering species, has been the parent of many hybrids that resemble it in shape but have much larger flowers of many different colours. There are two general types of Streptocarpus in South Africa – those with a rosette of leaves that look like primrose leaves, hence the common name, and the other type whose plants grow from one leaf. These leaves can be huge giants, nearly a metre long, down to tiny little plants with leaves only a few centimeters in length.
In the wild, this species occurs naturally from about East London in the south, to just north and inland of Durban, along the forests and gorges of coastal Kwa-Zulu-Natal. Many of our local Streptocarpus are either epiphytes, growing on the trunks of forest trees in amongst the mosses, ferns and orchids, or lithophytes, growing on rocks or rock faces and even ledges, where the soil is shallow and rich in humus. All you have to do is to copy the conditions in your garden or nursery and the plants are yours to grow. So far in KZN, I have really only come across two or three growers who have succeeded in keeping these plants alive in cultivation for any length of time.
The seed dispersal method of these plants is unusual and the botanists have recognised this by using the scientific name of Streptocarpus meaning streptos = twisted and karpos = fruit. In Streps, as they are often known, the seed capsule is a longish series of strips that are twisted together to form a hollow cylinder that contains the fine seeds within. As the cylinder matures and eventually dries out, it untwists to release seeds into the atmosphere, and again, when it gets wet after drying out, it re-opens to release seeds into the film of water that is around the capsule.
I have always found it best to sow the seed fresh on a seedling mixture of one part finely sieved compost to one part of fairly coarse river sand. I do not add any fertiliser to this mixture as I do not want too many pathogens to germinate. Water the seedlings by laying the tray in a shallow bath of water that then soaks into the seedling mix from below. The leaves then do not get wet and will be less prone to pathogen attack.
Once the seeds germinate and the new proper leaves are forming, you can begin giving a little fertilizer in low concentrations, in liquid or soluble form, to get the young plants on their way. Organic fertilizers are usually the best initially; use half the dilution ratio that appears on the label of the container. Fertilizer is applied by the same method as the watering - from underneath. Once the leaves are about 25mm in length then carefully transfer the seedlings into their own individual containers.
Apply fertilizer every ten days or so in the growing season. Once the winter has started (by the end of March to mid-April) start to dry the plants off a little by reducing the amount of watering, and stop feeding all together. The young plants go into suspended animation for a few months until the next spring - in about August to September. (The further inland and higher up in altitude you are from the coast, will mean that there is a delay of 4 to 6 weeks before plants start to grow in the spring.)
These plants are really for the serious collectors or for someone that buys a pot-plant for display in the home.