The Cape primrose (Streptocarpus), also known as African violet because of its origin, is a genus of plants in the gesneriad family (Gesneriaceae) comprising about 135 different species.
Many hybrid varieties are used as houseplants but are not entirely uncomplicated in terms of care.
Origin and Distribution
Most of the species of the Cape primrose originate from tropical Africa. There you can mainly find them in South Africa, Tanzania, and Madagascar.
Only four species of the genus are native to Asia, such as Streptocarpus burmanicus in Myanmar, Streptocarpus orientalis in Thailand, or Streptocarpus sumatranus on Sumatra.
Due to its tropical origin, the warmth-loving Cape primrose can only be cultivated in areas with cold winters as a houseplant.
During the hot summer months or in areas without frost, you can also cultivate the plant on the balcony or terrace.
Thereby mainly different hybrid forms are used. The actual species on the other hand are very rare as houseplants.
Appearance and Growth
Cape primrose hybrids kept in indoor culture are usually perennial and evergreen plants that grow herbaceously and do not lignify.
Many popular varieties form long shoot axes that hang over the edge of the planter. These varieties are perfect for planting in hanging baskets, where they can grow their shoots downward.
Other varieties also develop fairly long shoot axes, but they remain independently upright. These varieties are usually easy to cultivate on a windowsill.
Streptocarpus usually only grows between 4 and 8 inches (10 and 20 cm) tall.
Many Cape primrose hybrids develop tall, often finely hairy, and oblong to elliptical-shaped stem leaves arranged in basal rosettes.
Some varieties like Streptocarpus wendlandii, on the other hand, develop only a single leaf, up to 36 inches (90 cm) long. This leaf continues to grow steadily or subsequently dies after forming a new leaf.
These leaves must not rest on the substrate, otherwise, they will rot. Usually, the leaves are green, but there are also varieties with variegated foliage.
Flowers and Flowering Time
The five-petaled funnel flowers, reminiscent of orchids, appear between April and September.
Cape primrose is a very persistent flowering plant. It constantly forms new flowers and therefore looks very decorative.
Depending on the variety, several or even a single flower grows on a stem. These can be monochromatic to multicolored.
The color palette is very extensive, especially for the hybrid forms, and ranges from white to red and pink to blue and purple in various shades.
Fruits and Seeds
After blooming, the plant forms cylindrical twisted fruits. The spiral capsules contain numerous, very fine seeds.
You can prolong the flowering period of the Cape primrose by removing faded stems in time to hinder fruit development. The plant will subsequently invest its energy in the formation of new flowers.
Is Cape Primrose Poisonous?
The Cape primrose is considered to be non-toxic. However, its leaf sap can cause an itchy rash in sensitive people. Therefore, it is better to wear garden gloves when caring for the plant.
Location and Temperature
As a true plant of the tropics, Cape primrose prefers a bright location with high humidity and a warm ambient temperature.
If possible, place the pot directly against an east or west-facing window, as the plant needs light. But be careful, as too much intense sunlight is harmful to the plant.
If the plant faces south, you should provide shade during midday. In addition, the location should be airy, but not draughty, and at least 59 °F (15 °C) warm all year round.
During the flowering period, the optimum temperature is 72 to 77 °F (22 to 25 °C), and the humidity should be at least 60 percent, preferably even more.
Substrate for Cape Primrose
The pretty blooms will only develop if the Cape primrose resides in soil suitable for its needs. In its natural habitats, the plant grows in the loose, humus-rich soils of rainforests, so the potting substrate should be composed accordingly.
For this purpose, mix humic, peat-free potting soil about half with loose coco soil.
Planting and Repotting Cape Primrose
The roots of the Cape primrose grow just below the surface of the substrate. And in addition, the root ball can become quite wide.
Therefore, choose a wide plant pot rather than a deep one. The right time to repot is when the planter is well-rooted.
Watering the Cape Primrose
Proper watering of the Cape primrose requires some tact because the plant wants to be kept evenly moist. But only lightly, because excessive wetness and especially waterlogging has an extremely harmful effect.
Therefore, always water when the top layer of the substrate has dried off, but the entire pot is not yet completely dry. Always check the necessity first by thumb test.
Use room-warm rainwater or stale tap water for watering and be careful not to wet the leaves or the flowers. Always water from the bottom and also refrain from spraying the Cape primrose, as the leaves tend to rot. Remove excess water from the saucer or planter promptly.
Fertilizing Cape Primrose Properly
Fertilize your Cape primrose every 14 days between March and October with a liquid flowering plant fertilizer, administered along with the watering. Never fertilize on the dry substrate, but always moisten it.
Pruning Cape Primrose Properly
Regular pruning is not necessary for the Cape primrose. You should only remove withered, dried, and diseased plant parts regularly with a sharp and disinfected pruning tool.
But do not simply tear off the relevant parts of the plant, because this would facilitate the entry of fungi, bacteria, and other pathogens.
Propagating Cape Primrose
As demanding as the Cape primrose often is in terms of its care, its propagation is uncomplicated. Especially the vegetative propagation via cuttings and leaf cuttings is easy even for laymen.
Naturally, you can only obtain leaf cuttings from the species with several leaves. The single-leaved rotary fruit species are unsuitable for this purpose.
Here’s how it works:
- Cut off a healthy leaf in the spring.
- Cut it crosswise into three to four parts.
- Stick the partial leaves about 0.5 inch (1 cm) deep into growing medium.
- Support them with matchsticks or other wooden sticks if necessary.
Place the planting pots in a bright and warm window spot and keep the substrate slightly moist at all times.
Do not stretch foil or similar over the cuttings as this will encourage rotting. Instead, use willow water for irrigation, as this encourages root formation.
Within a few weeks, small Cape primrose plants with their own roots will form along the cut edges. Separate these from the leaf cuttings and pot them separately in their own pots starting at a growth height of about 3 inches (7 cm).
Hanging Cape primrose species and hybrids such as the false African violet (Streptocarpus saxorum) are very suitable for propagation via shoot cuttings.
Here’s how to do it:
- In spring, cut head cuttings with a length of 3-4 inches (7-10 cm).
- Remove all but the top pair of leaves.
- Plant the cuttings individually in pots filled with a growing medium.
Also, place these containers in a bright and warm window spot. Keep the substrate evenly moist, but not wet.
As soon as strong roots have formed, the cutting will sprout anew. Now repot it into a larger container if necessary.
Wintering Cape Primrose
Proper overwintering is the most difficult phase in the life of the Cape primrose. If you want to be on the safe side, simply leave the plant in its proven location and reduce the temperature here to about 59 °F (15 °C).
This approach is practical, but not necessarily feasible, especially in the living room. In principle, the Cape primrose can stay there all year round at warm temperatures, but the flowering threatens to fail if there is no break in vegetation.
So it is preferable to place it in a comparable but cooler spot, such as the bedroom. Water the plant only a little, and stop fertilizing it starting in October.
Slowly acclimate the plant to warmer temperatures again starting in February/March.
Species and Varieties
There are about 135 different Cape primrose species, some of which are also cultivated as houseplants.
However, most of the varieties in indoor cultivation are specially bred hybrid varieties, of which there are several hundred different ones. To list them all here would go beyond the scope of this article.
Nevertheless, we would like to present the most beautiful varieties to you.
This hanging growing and very lush flowering species originates from Tanzania and Kenya, but you can also keep them indoors.
Most varieties produce bright blue flowers, for example, the very popular variety ‘Blue Paul’. But there are also white or pink flowering forms.
This species, which originates from South Africa and is rarely cultivated, delights with its numerous pure white calyxes.
This is one of the single-leaf varieties, which forms only a single, but very large leaf.
Streptocarpus wendlandii blooms very long and shows pretty purple flowers, but dies after flowering. The species originates from South Africa.
This species also forms only one leaf, but with a length of up to 12 inches (30 cm), it is very long.
The plant, which also comes from South Africa, can grow up to 12 inches (30 cm) high and flowers very persistently. The continuously newly formed flowers are white.
The numerous Streptocarpus hybrids are very different on the outside. Some varieties can grow very large and develop leaves up to 20 inches (50 cm) long, while others show an upright growth habit, still others a prostrate or drooping one.
However, the differences are particularly great in the flower colors. Monochromatic varieties in a wide range of shades are represented as well as bicolored or even tricolored varieties.
- ‘Harlequin’: Growing height up to 14 inches (35 cm) withtricolored flowers.
- ‘Asia’: Growth height up to 12 inches (30 cm), forming white flowers with a ruffled edge.
- ‘Iona’: Deep red flowers that bloom up to ten months a year.
- ‘Roulette Cherry’: Growth height up to 14 inches (35 cm), pink flowers with white gorge.