Horticulture Magazine

Streptocarpus ‘Cape Primrose’ Plant Care & Growing Tips

a single purple flower of Streptocarpus Saxorum

Streptocarpus Overview

Official Plant NameStreptocarpus
Common Name(s)Cape Primrose
Plant TypeHouseplant
Native AreaAfrica
Hardiness RatingH1C
ToxicityNone
FoliageEvergreen
FlowersMany colours – often white/violet
When To Sow (Indoors)Year-round
Flowering MonthsMarch, April, May, June, July, August, September, October
Sunlight

Preferred
Partial Shade

Exposure
Indoors

Size

Height
0.1 – 0.5M

Spread
0.1 – 0.5M

Bloom Time
March – October

Soil

Preferred
Chalk, clay, sand

Moisture
Moist but well-drained

pH
Slightly Acidic / Neutral

Streptocarpuses or ‘Cape Primroses’ are the anthophile’s dream houseplants.

Compact and easy care, these tender evergreens are made to order for climatic conditions found in homes in European regions.

Their foliage comprises attractive rosettes of rich green leaves. And they produce masses of small flowers for from six months to a year!

Not only are their colours wonderfully varied, many are effectively bi-coloured.

Cape Primrose is a tender – make that ‘very tender’ – evergreen. This puts the gardener in an unusual quandary: how do you grow a ‘very tender’ evergreen?

The obvious answer is, “Why, in a greenhouse, of course”. That’s true but for Cape Primrose the answer can be extended.

Though this plant is intolerant of cold and also succumbs to its fair share of pests, it has a singular strength: this delightful wildflower is a regular homebody!

Cape Primroses are nature-made houseplants for European and American climates, and what’s more, they are flowering houseplants that produce eye-popping little blooms for from six months to nearly the whole year.

Impressed? You’ll be even more impressed when you get to know how varied their flowers are – soft and soothing, and also dazzling and intense. 

The Streptocarpus genus falls in the Gesneriad family comprising numerous genera that are relatively little-known but include many types of plants, the vast majority of which bear unusual and attractive flowers.

Streptocarpus includes upwards of 150 species that are native (only) to the African continent from Guinea and Sierra Leone on the western coast across to Sudan down to South Africa, plus Madagascar.

The names Streptocarpus and Cape Primrose are often used synonymously, though not by botanists. 

Cape Primroses are, as expressed earlier, nature-made houseplants for European and American climates (excluding the northern regions of the countries) because the climatic conditions in the average home are quite similar to those of their native habitats.

With only some effort conditions inside the house can even be made to mimic those native-region climates. Another positive attribute is that they are compact plants that are ideal for sunny windowsills.

Streptocarpus houseplants can transform any room, bringing a little bit of garden into the home.

Streptocarpus 'Harlequin Delft'
A Very Pretty Cape Primrose Variety (‘Harlequin Delft’) in Complementary Purple and White Colours

Background & Origins

James Bowie from Kew collected the first Streptocarpus species, Streptocarpus Lindl, from the Western Cape. That and other Streptocarpus species were first sent to Great Britain from South Africa in the 1820s and 1850s.

Thereafter other species from other regions in Africa were also sent to England.

Hybridisation got underway in the 1880s at Kew Gardens with the 1890s seeing a sharp rise in the plant’s horticulture which in time resulted in the popular cultivars of our day.

The parent species for these are S. rexii, S. parviflorus, and S. dunnii. All three of them are native to South Africa, therefore ‘Cape Primrose’ is quite an accurate name for all the many cultivars.

As it happens, among botanists ‘Cape Primrose’ is also the name of a clade in Streptocarpus, ITS clade VII whose members are native to the Western Cape northeast to Limpopo (in South Africa). And this clade includes, among other species, aforementioned S. rexii and S. parviflorus which are two of the three original parents of Cape Primrose cultivars. Accurate name, eh?

The Cape Primrose clade and the species of interest to us are among the youngest ones in Genus Streptocarpus, having evolved from ancestors in central tropical Africa. It dates back to only about 1.11 to 3.5 million years ago.

Streptocarpus "Lola" with purple and snow white flowers
Snow White and Deep Violet Makes for Great Visual Impact on This Lovely Cultivar (‘Lola’)

Genus Streptocarpus

For botanists, Genus Streptocarpus is a study in diversity while for gardeners the genus’s Cape Primrose cultivars make for a set of fairly (though not overly) uniform varieties.

These mainly differ to a considerable extent in the colourations of the flowers, a small extent in their forms, and to some extent in the length of the blooming period.

Most varieties bloom from spring through autumn while climatic conditions, watering and feeding strongly influence the length of the blooming season.

Streptocarpus, colloquially ’Streps’, are evergreen plants with clump-forming bushy habits. They grow to heights of 25 to 30 centimetres, and the spread of a particular variety or particular plant is usually a shade more, sometimes a shade less, than its height.

Their foliage is in the form of a basal rosette with the leaves varying mainly from oblong to strap-shaped. They have pronounced ribbing and are often textured or wrinkled, and have a soft hairy fuzz.

The flower stalks emerge as if from the medial end of leaves, thus very artistically rising from the middle of the rosette.

Flowers are usually from 2.5 to 4 centimetres in width with a few varieties producing larger flowers. They have five petals and are salverform or flared trumpet-shaped.

They occur in bright and even saturated tones, and also in soft, soothing pastel shades.

Many are in hues of pinks and purples but a few bear flowers in other colours including white and true red.

Finally, flowers usually have accents, blotches, veining, or patterning on the lower petals making such blooms effectively bi-coloured.

cape primrose ‘Texas Hot Chili’ with pink and white flowers
Some Streptocarpus Varieties Have Sparkling Bright Green Foliage

Common Varieties

Apart from Cape Primrose’s many merits related above, this happy little wildflower possesses a remarkable talent in collecting RHS Awards of Garden Merit – it has garnered 27 of them. All but three of our Top Twelve choices are AGM winners.

The exceptions are ’Watermelon Wine’ selected for being one of the only true reds and a self at that, ‘Anne’ for its double form but even more for the intense violet, and ‘Zoe’ for its unusually lovely colouration and patterning.

‘Harlequin Blue’ has to lead our rundown because it was the Chelsea Plant of the Year for 2010. One might say that its flowers are precisely bi-coloured to perfection. The entirety of the upper two petals is a soft purplish-blue while the entirety of the lower three is a pale creamy yellow. A dark violet streak running from the throat out to the edge divides the two sets of petals and the two colours! This variety blooms from spring through autumn.

‘White Butterfly’ possesses two rare attributes. Though its flowers in size are at the lower limit at 2.5 centimetres this variety is possibly the only one to produce pure white ‘self’ flowers. And, second, it is floriferous, and it is one of those wonders that blooms all 12 months of the year!

’Tina’ is not particularly distinguished in the unremarkable pink tone of its flowers with darker splotches on the lower petals but it is distinguished in the size of its flowers which, at up to 6 centimetres, are massive for Cape Primrose. The leaves are of quite a dark shade and are oblong. It flowers from spring through autumn.

‘Charlotte’ has bright green foliage from which arise exquisitely hued blooms. They are a pale pastel lilac with the lower petals displaying blotches of an equally pale, pastel complementary yellow with a similarly coloured throat. It blooms from spring through autumn.

‘Crystal Ice’ has snowy white flowers with delicate, veined accents of purple to violet on the lower petals. The leaves are a rich, dark shade. And it is remarkable for being one of those relatively few year-round flowering wonders.

Streptocarpus plants in a black container
The Soft and Gentle Appeal of Year-Round Bloomer ‘Crystal Ice’

‘Sioned’ has medium-green strap-like leaves and bears particularly delightful flowers. They are off-white with the lower petals accented with a variegated and veined blotch of magenta-pink that starts in the throat and bleeds away near the outer edges. It blooms from spring through autumn.

‘Burgundy Ice’ produces flowers that are as unusual as they are eye-pulling. Their ground colour is a rich maroon of a burgundy-blackcurrant tone with subtly darker veining and gradation. These saturated tones are accented with a white throat, central white speckles, and fine white edging. It blooms from spring through autumn.

‘Stella’ has strap-shaped leaves of a very rich shade. The flowers are of an even richer tone of purple with subtle streaking, veining and gradation in a slightly darker violet so as to produce a shifting colour effect. The rich, deep hues and the gradation produce the effect of the petals appearing to be glossy. This variety blooms from spring through autumn.

‘Watermelon Wine’ has foliage of a very pleasing bright mid-green shade. The spectacular flowers are of a single colour, a solid lipstick red with slightly darker shadings on the lower petals which only enhances the intensity of the hue. It blooms from spring through autumn.

‘Anne’ has spanking bright green leaves that are particularly wrinkled and textured. It is one of the few varieties to produce double flowers with the inner petals being ruffled or half-closed. The flowers are ‘selfs’ in a tone of intense violet all through. It does not bloom as long as most other varieties, producing flowers from mid-spring to early autumn.

‘Zoe’ has attractive foliage of nearly an emerald green tone. It produces flowers with extraordinary colourations. Each flower is in a gradated shade of purple from pale lilac to deep, rich purple with veining in darker shades over lighter shades all over. Streaks of deep purple run out from the throat on the three lower petals which are further embellished with creamy yellow in the throat and the medial sides, just as the upper petals are similarly accented with white. It blooms from spring through autumn.

‘Polka-Dot Purple’ has leaves of a particularly light, bright green. It produces trumpet-shaped flowers that are quite startling. They are of a deep, rich purple hue with white streaks radiating from the centre, broad white edging, and very many white speckles or ‘polka dots.’ The overall effect is one of purple and white marbling of a kind. This fantastic variety blooms year-round.

‘Polka-Dot Purple’ Cape Primrose with purple and white hues
The Dazzling Charms of Year-Round Bloomer ‘Polka-Dot Purple’

Habitat & Growing Conditions

In their native habitats, Streptocarpus species often grow at the edge of and in forests, and also under the forest canopy where they thrive in shade in humid conditions.

Other species also grow amidst rocks and on rocky overhangs and outcrops, but even on such ground they are usually found in the shelter and shade of trees and woods.

Cape Primrose varieties will flourish when they get warm days and cool nights yet these plants are very sensitive to temperature extremes and cannot tolerate temperatures either around even 5°C or nearing 26°C.

At a hardiness rating of H1C they are frost tender yet cannot be kept outdoors in even part sun in the summer as they are also ‘sun tender’!

Normal conditions in most homes in a spot where they can get indirect light or only early morning direct sunlight suits these plants just about perfectly. They are more amenable to a somewhat humid environment than to a dry one.

Where to Plant Cape Primrose

It is very difficult to plant Streps outdoors because in the small band of land along the south-western and southern coast of England where the winter temperatures won’t kill these plants, the summer sun and heat will.

If you are located in these very mild regions and you want to try to grow these plants outdoors, what you can do is to site them in near-full shade, especially in summer when they should get no more than dappled or filtered morning sun.

Even out of summer they should not get full sun.

In general, if you would like to have Cape Primrose sitting outdoors then simply grow them in containers that you can put outdoors according to your region’s climate and the season, and bring them indoors as and when necessary. 

The best plan is to grow these pretty little flowering varieties as houseplants following the guidance in the following section. That said, they are ideally suited to windowsills except south-facing ones that get direct sun in the warmer months.

purple and white streptocarpus in terracotta pots
Cape Primrose – Perfect for Windowsills or French Windows

Feeding, Care & Growing Tips

Soil Requirements

To grow Cape Primrose varieties as houseplants use a soil consisting of potting mix and garden compost with gravel or perlite or both mixed in to facilitate drainage. These plants require excellent drainage so also make sure that the container or pot has drainage holes.

Soil pH from Moderately Acidic to Slightly Alkaline will do though optimally it should be from Slightly Acidic to Neutral – pH 6.1 to 7.3.

Temperature & Aspect

These temperature-sensitive plants will do best at daytime temperatures hovering around 21°C and nighttime ones of around 15°C.

Plants should get several hours of indirect daylight. They may get direct early morning sun out of summer.

A north- or east-facing windowsill would be a very good location. They can be put on a south-facing windowsill during winter.

You can filter sunlight by shielding Streps with a thin or gauzy curtain.

Growing From Seed

Cape Primroses can be grown from seed or propagated from leaf cuttings. They are easy to find as potted plants or bare-root plugs.

Seeds are very small. Sow them in spring or summer by simply scattering them on top of the soil, either in a seed tray or pot. They need light to germinate so do not cover them with soil.

Instead, consider covering the tray or pot with clear plastic cling film. This will lock in moisture that is helpful for germination and early growth. Water well.

The tray or pot should be kept in indirect but bright daylight and in a temperature range of 19 to 23°C.

Continue to water such that the soil stays moist. Seeds should germinate within a fortnight.

Slow-growing initially, plants grown from seed will start to flower inside five months.

After seedlings have two true leaves they can be potted into individual pots, which should be of a small size. At this time reduce the amount of watering.

violet and white crinkled flowers of streptocarpus
A Few Varieties Produce Double Form Flowers with Ruffled Central Petals

Propagation

Propagating Streps from leaves is, well, fun and easy. Actually this particular ‘feature’ offers an interesting and enjoyable way to introduce children to gardening.

Cut off a young and healthy leaf that has attained its full size just at the petiole. Then cut it crosswise into four sections or lengthwise on each side of the midrib into two.

Insert the cuttings with the cut side down to about 2 centimetres into the type of soil described above. Water well, and – as for seeds – cover the tray or pot with clear plastic film.

The cuttings should be kept in the same temperature range as stated above as you continue watering such that the soil stays moist.

In four to five weeks small new plants or plantlets will form from the cut ends of the cuttings. There will be several to many such plantlets. After they develop two sets of leaves they will need to be divided and potted on. 

Watering

Water regularly but in moderation to avoid root rot. You may water just when the soil dries out. This precaution is especially necessary during the winter months.

As temperature-sensitive as these plants are, one needs to be careful about the water temperature as well.

During winter do not water plants directly after filling a watering can from the tap as the water will be quite cold – fill water in the can or in some container a day in advance so that the plants can be watered with water at room temperature.

This precaution is critical if you live in one of the colder regions of the country. Similarly, if you are experiencing hot weather, be sure that the water you collect from the tap is not even lukewarm.

Feeding

Although Cape Primroses greatly benefit from regular feeding, do not feed a young plant as it does not have a well-developed root system. Wait until plants are six months or more before you feed for the first time.

In spring and summer you may feed the plants about every three weeks with a 10-10-10, 5-10-10 liquid fertiliser, or a houseplant liquid fertiliser.

It should be diluted to double the specified strength (that is, at a greater dilution). You may continue feeding at a greater dilution and reduced frequency through autumn and winter.

Finally, as Cape Primroses mature, they grow horizontally forming new clumps. Any time during spring you can divide an overgrown plant by simply separating clumps (vertically), and re-potting them.  

streptocarpus variety 'Hope' with red blooms
Not too Many Varieties of Cape Primrose have Red Flowers (Var. ‘Hope’)

Common Diseases & Problems

Streps are sensitive plants and may suffer from foliage problems, in particular leaf rot and leaf scorch.

Leaves may start to rot from the lower ends because of excessive watering, wrong type of soil, poor drainage, or any combination of these factors.

If you encounter leaf rot, remove rotting leaves from the petiole and correct whatever is wrong.

Leaves may get scorched and browned from too much direct sunlight, in which case simply change the position of the plant.

Though some varieties are a little more robust than others, all varieties can succumb to thrips, mealybugs, vine weevil, glasshouse leafhoppers, and tarsonemid mite.

All these pests can be controlled but the best course of action is to regularly carefully inspect each plant, particularly during spring and summer, so that any infestation can be spotted early and dealt with before it spreads and becomes hard to control.

Where to Buy Streptocarpus

Cape Primroses, already popular to begin with, are rising in the popularity sweepstakes.

purple panda cape primrose flowers with half-and-half violet and white colours
‘Purple Panda’ – a Very Appealing and Popular Cultivar

As a consequence they are so widely available that you should be able to find several varieties at your local garden centre or nursery.

Almost every online plant and shrub merchant carries a good assortment of Streptocarpus varieties as potted plants or bare-root plugs. And if a friend or neighbour has a plant, just ‘borrow’ a leaf!

© 2021 TKO DIGITAL LTD | Registered in England and Wales No. 10866260 | This website uses cookies.