Streptocarpus johannis

L.L.Britten
Family: Gesneriaceae
Common name: Cape primrose

Streptocarpus johannis

A rewarding pot plant, unusually stemless, with a cluster of whitish to pale violet, flat-faced flowers and soft green leaves that can be grown indoors or in a sheltered spot outdoors.

Description
A perennial herb with a horizontal rhizome and a loose rosette of lightly hairy leaves up to 300 mm long. No stems are present and the leaves grow continuously from the base. Each leaf is actually an individual plant with its own roots and flowering stems. Whitish to pale violet, flat-faced flowers sometimes have a bit of yellow colouring in the throat. Clusters of up to 12 flowers per inflorescence are held above the base of leaves on a flower stalk up to 300 mm long. Each leaf in the rosette can bear a flower stalk and so the flowering period lasts from October to December.

Flower

The asymmetrical flower typically has two lips, the upper is 2-lobed and the lower 3- lobed. The flower tube is cylindrical with a bulbous base leading to a strongly curved corolla tube with a flattened end . The fruit is a spirally twisted cylindrical capsule which feels velvety while forming; when ripe it is dry and the seedpod twists open along two slits, releasing masses of very fine dark seeds.

Pod and seeds

This plant is relatively fast growing as it takes one year to grow to flowering size.

Distribution and Habitat
Steptocarpus johannis occurs naturally in forests, growing in soil banks or on rocks and occurs from the coast to altitudes of 1 650 m.

Well suited to living in woodland, the plants grow best in conditions that resemble those found in their natural habitat, therefore they require rain in summer, very good drainage and some shade, preferably bright, dappled light, good ventilation and not too much heat and moist (not wet) soil conditions. Occurs from the Eastern Cape to KwaZulu-Natal.

Derivation of name and historical aspects
The name Streptocarpus is derived from the Greek words streptos meaning twisted and carpus meaning fruit, which is a perfect description of the plants' twisted seedpods. Commonly known as Cape primroses, which alludes to the appearance of the leaves, as they are not related to primroses at all, and they were first discovered near the Cape.

The species johannis is derived from Port St Johns where it was first collected.

Streptocarpus belongs to the large family Gesneriaceae, mostly tropical and subtropical herbs, with ± 130 genera, and ± 2900 species world-wide. There are eight genera in Africa, and the one genus, Streptocarpus in South Africa has ± 51 species. Other noteworthy members of this family that are economically important in horticulture are Gloxinia and the African violet. The family is named after Konrad Gesner who was a Swiss scholar, and in 1963, 30 years after his death, his name was given to this family.

Conservation Status
Many of the Streptocarpus species are very specific in their distribution and occur only in small populations, making them vulnerable to disturbance. Streptocarpus johannis does not have a rare, endangered or threatened status at the moment but S. kentaniensis and S. formosus are threatened.

Ecology
Gesneriaceae are often epiphytic (growing on trees) or lithophytic (growing on rocks), The very small seed is wind distributed.

Uses and cultural aspects
In mainly Europe and America, Streptocarpus hybrids are very popular indoor potplants. Only a few species were used as mother stock to develop the hybrids and, with great variation within species which easily hybridize, there is still much scope in developing new hybrids. There is much interest and a growing demand for Streptocarpus in South Africa.

Leaves and flowers

Growing Streptocarpus johannis

Many of the Streptocarpus species make beautiful potplants and garden plants for the shade. Indoors, ensure a warm spot with good light but no direct sunlight as the plants burn easily. Many Streptocarpus species are displayed in the Conservatory, Camphor Avenue, the Dell and in pots in the Visitors Centre at Kirstenbosch, where they thrive.

It is very important that the plants should not be over-watered to prevent rotting and fungal problems. Allow them to get quite dry between watering periods; they can be allowed to wilt slightly as they have the ability to recover very well, but be aware that severe wilting can be a sign of root rot caused by over-watering, so check the medium to see that this is not the case.

Remove all dead flowers and yellowing leaves as these encourage fungal growth, and to keep the plants looking attractive. If fungus is found on any part of the plant, pinch out the affected parts and treat with a suitable fungicide.

Regular feeding is recommended once the plant's roots appear at the bottom of the pot.

Streptocarpus can easily be grown from seed but only species will come true from seed. For hybrids, cuttings or division will need to be used to keep all the new plants identical to the parent plant.

All propagation is best done in spring which is the start of the growing season, most of the plants rest during winter. This resting will cause them to need very little watering and often abscission layers will be seen (picture provided). This is where the tip of the leaf turns yellow then brown and then dies. It is a bit unsightly but causes no permanent damage to the leaf which continues to grow from the base. It is a natural reaction of the plant to unfavourable environmental conditions such as cold or drought. The dry leaf ends can be pulled or cut off.

For seed sowing, mix a pinch of the dust-like seed with a small amount of sand to assist with spreading the seed evenly when sowing. Use a well-drained medium that is not too coarse. Cover with a very thin covering of sand, keep out of direct sun but warm and moist (not wet), till the young seedlings appear. Germination usually takes 3 to 4 weeks, do not allow the seedlings to dry out.

Cuttings

Streptocarpus belongs to a small group of plants that can be propagated from a single leaf; the best method is leaf cuttings ideally taken in spring and early summer. A variety of mediums can be used as long as they are well drained. Sand, bark, palm fibre and polystyrene or vermiculite in different ratios are all suitable. At Kirstenbosch we use 40% bark, 40% polystyrene and 20% sand. Water the medium well and treat with a suitable fungicide before using. Select healthy, youngish leaves from the centre of the plant and cut off using a sharp knife or blade. Remember that the most active region of the leaf is near the base where the growing region (meristem) is present. If it is a small leaf, insert the cut end of the leaf into a rooting hormone and then into the medium. Larger leaves can be cut into 30 mm strips. Always take note of which way is the leaf cutting should be orientated before dipping into a rooting hormone and place into the medium but not too deep, as this will encourage rot. Alternatively, cut along either side of the midrib and treat in the same manner. Depending on the species, plantlets will form along the base of the cut in one to three months. When the plantlets are well established (30-50 mm), the old leaf can be teased out from the medium and the plantlets potted up, usually between 6-12 months.

The potting medium we use at Kirstenbosch consists of the following: 1 part good compost (2 wheelbarrows), 1 part coarse sand (2 wheelbarrows, 1 part palm fibre (10 blocks = 2 wheelbarrows). Add a small amount of organic fertilizer.

Mature plants often lose their vigour after three to five years and should be replaced with younger plants.

Worms are the most troublesome pests of Streptocarpus, they can either be hand collected or sprayed with a suitable poison.

References and further reading

  • Burtt, B.L. & Hilliard, O.M.. 1971. Streptocarpus, an African plant study. University of Natal Press, Pietermaritzburg.
  • Dibley, R. & Dibley, G. 1995. Streptocarpus. Cassell, London.
  • Leistner, O.A. (ed.). 2000. Seeds plants of southern Africa : families and genera. Strelitzia 10. National Botanical Institute, Pretoria.

 

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Author
Cherise Viljoen
Kirstenbosch Garden
October 2006

 

 

 

 

 

 

 


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