I always know that Autumn is approaching when I see my Streptocarpus start to flower.
They are sometimes called Cape Primrose referring to their nativity to South Africa and semblance to a Primula.
The following is an adapted excerpt from the 1906 text “Hortus Veitchii”:
- The first Streptocarpus to reach British gardens was Streptocarpus Rexii. This species was sent to Kew in 1824 by Mr Bowie, who was His Majesty’s collector in South Africa. The plant was found on the estate of Mr George Rex, after whom it was named. Following Streptocarpus rexii came Streptocarous polyantha from Natal. It was accidentally introduced to Kew in 1853 in material surrounding trunks of tree ferns sent from Natal by Captain Garden. Streptocarpus gardeni, also introduced in 1853 from the same country was named for Captain Garden, who sent seeds to Kew. In 1860, Mr Wilson Saunders sent a specimen to Kew, and it was eventually named Streptocarpus saundersii. In 1882, the caulescent species, Streptocarpus kirkii, was sent to Kew by Sir John Kirk. Streptocarpus caulescens, another caulescent species, followed in 1886. In 1887, “Streptocarpus parviflora” (probably Streptocarpus parviflorus, and referred to hereafter as such) was raised from seed brought in from Grahamstown by Mr Watson of Kew. A similar plant raised from seed by Mr Lynch of the Cambridge Botanic Gardens, was eventually named Streptocarpus lutea. The next plant to be introduced, Streptocarpus dunnii, played an important role in the production of “beautiful hybrids” of the day. In 1884, seed was collected in the mountains of the Transvaal gold fields, and sent to Kew by Mr E. G. Dunn of Claremont, Cape Town. It was a unifoliate species with “rose or salmon red colour”. It first flowered at Kew in 1886. In 1890, Streptocarpus galpini was introduced to Kew by Mr E Galpin, who found it on the “Bearded Man” peak that forms one of the boundaries of Swaziland. Streptocarpus wendlandii was sent in 1887 from Transvaal to Naples to “Messrs Damman” (i.e. two or more men with the last name ‘Damman’ – possibly nurserymen). It first appeared in England at Kew in seed contained in soil attached to tree ferns from South Africa. It flowered at Kew in 1895. A hybrid named “Streptocarpus x Dyeri” was raised at Kew by crossing Streptocarpus wendlandii with Streptocarpus dunii. “Streptocarpus faninii” (not currently listed, could this perhaps be referring to Streptocarpus fanniniae?), is apparently noteworthy because of its contribution to many of the “more beautiful hybrids”. Hortus Veitchii states that the first hybrid Streptocarpus recorded was “Streptocarpus x Greenii”, which was the progeny of S. saundersii and S. rexii. It was raised by Mr Charles Green, who was at the time the gardener to Sir George Mackay of Pendell Court. This specimen was apparently never widely grown and did not contribute to the “present garden race”.
- The initial step towards the “beautiful forms” in cultivation at the time was taken by the Curator of Kew. He raised the hybrid “Streptocarpus x Kewensis” by crossing S. rexii and S. dunii. However, he had previously also raised S. parviflorus x S. rexii. A coloured plate of the progeny was published in 1886. In 1887, another Kew-raised hybrid flowered. It was a hybrid of S. parviflorus and S. dunnii, and received the name of S. x Watsoni, after Mr Watson who raised the seed. In 1887, two hybrids (S. x Kewensis and S. x Watsoni) were crossed with each other and their parents in all combinations. A host of progeny resulted with marked differences in colour, size, form and flower, and many were “decidedly attractive”. A selection of these were obtained by Heal, who crossed them with each other and with the red-flowered S. dunii. Many of these are now known as “Veitch’s Original Hybrids”. Breeding continued using these hybrids.
Streptocarpus seed pod, showing spiralling form
Young rosulate Streptocarpus, whole plant
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: 18°C-25°C (64.4°F-77°F). They can be taken down to 10°C (50°F) 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 OK. Even in dimmer light, they will flower – but less floriferously.
Water: Water only once the soil is almost dry. Some grower prefer to water only when the leaves have just started to wilt (or just before). They recover very well from dehydration, and 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 fertiliser.
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 are 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 mealy bug. 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 (see picture gallery below) 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).
Streptocarpus seedling showing normally rudimentary second cotyledon
Propagation is usually either by seed or leaf cuttings. Some species produce plantlets from the roots, which can be used to propagate the plant. Mature clumps of plants can also be divided up and repotted.
Streptocarpus species seed that has been self pollinated will grow true to type.
Self pollinated hybrid seed will not grow true to type. The only way to propagate hybrid plants and retain the characteristics of the hybrid, is by leaf propagation (or other types of vegetative cloning)
For Streptocarpus subgenus Streptocarpus:
By seed: Streptocarpus seed is generally very fine (see image gallery below). To germinate, the seed must be scattered thinly on top of potting mix, as they require light to germinate. The pot they are sown in must be covered in clear plastic “cling film” to keep up the humidity. Keep the sown seed where it will get bright, indirect light, and remain about 18-20 degrees Celsius. Keep them out of direct sunlight.
By leaf: A Streptocarpus leaf can be severed at the base (but above where flowers arise), and potted, base-down, in a few centimetres of potting mix. Place a clear plastic bag over the pot and secure with a rubber band to keep up the humidity. Streptocarpus leaves have a high concentration of cytokinin (a type of rooting hormone), so the use of artificial rooting hormones is unnecessary.
Leaf segments, cut either horizontally across the leaf, or vertically along the leaf (removing the midrib), can be used as cuttings in much the same way.
For unifoliates, this method is apparently less successful, but not impossible. However, it must be done before the plant flowers.
By root plantlet: Un-pot a plant that you know is susceptible to producing root plantlets (e.g. Streptocarpus johannis, and Streptocarpus ‘Falling Stars’. You will see, once the roots are exposed, whether any plantlets are formed.
Sometimes, these plantlets will be evident growing out of the holes at the bottom of the pot. You can then snip these plantlets off (preferably with their attached roots), and plant up as for leaf propagation above).
By clump division: You can divide a multi-crown clump into pieces (each with a root system), and plant up as for leaf propagation above.
For Streptocarpus subgenus Streptocarpella:
By seed: Streptocarpus seed is generally very fine. To germinate, the seed must be scattered thinly on top of potting mix, as they require light to germinate. The pot they are sown in must be covered in clear plastic “cling film” to keep up the humidity. Keep the sown seed where it will get bright, indirect light, and remain about 18-20 degrees Celsius. Keep them out of direct sunlight.
By stem cuttings: Cuttings of about 5–10 cm can be taken beneath a leaf node. When the cutting is placed in clean water, it will sprout roots. Keep the cuttings in bright, indirect light at about 18-20 degrees Celsius. Once the roots are about 5 cm long, you can pot up the cutting into the soil mixture mentioned above.