The Cape crusaders
They may look dainty, but these South African toughies can keep on flowering right through winter
SOME 16 years ago a small cardboard box was delivered to my door, containing a new variety of Cape primrose cushioned between a wad of shredded paper. I didn’t hold out much hope for the young houseplant with two or three puny leaves, but duly potted it up and placed it on a light, east-facing kitchen windowsill.
Over the next few weeks my new charge burst into life, throwing out a succession of much longer, narrow leaves. Eventually there was a gorgeous rosette of foliage that made the perfect foil for an endless supply of 12in stems carrying masses of white flowers with intricate blue markings.
Like most Cape primroses, this newcomer bloomed from about mid-spring until late autumn, but when others in my care were taking a breather, it showed no signs of giving up. In fact, the plant flowered for almost 12 months solid, only letting up when I had to deal with an attack by sap-sucking insects.
This revolutionary variety was Streptocarpus ‘Crystal Ice’, the world’s first all-year-flowering – sometimes called winter-flowering – Cape primrose. Bred by Dibley’s Nurseries of Ruthin, North Wales, it made the inside pages of many newspapers and magazines following its public debut at the RHS Westminster Show in January 2000. ‘Crystal Ice’ has now been joined by a host of other Cape primroses with a similar long period of interest. Their show-stopping displays are always welcome, whatever the season, but they really earn their keep during the colder months.
Cape primroses originate from South Africa, where they can be found growing on the ground, on rocky cliffs and in wooded ravines. Despite their common name, they are not related to primroses but belong to a family that includes African violets, achimenes and gloxinia, all of which are grown as houseplants in our climate.
We’ve been growing them undercover in Britain since the early 19th Century, but the first classic variety is largely considered to be ‘Constant Nymph’, a blue streptocarpus named after a 1924 novel by Margaret Kennedy. Unveiled in 1946 by the John Innes Horticultural Institution, it stood out from all its predecessors due to its increased vigour and greater flower power.
Today there are hundreds of varieties with flowers in many shades of white, yellow, blue, pink, red and purple. Apart from vibrant single colours, there are Cape primroses with petals that are adorned with contrasting stripes, veins or irregular markings, or heavily splashed with two or more colours.
For my money, the ones with the most striking flowers are the Harlequin series of Cape primroses. Crowned Chelsea Flower Show plant of the year in 2010, ‘Harlequin Blue’ has yellow lower petals and baby-blue upper ones, while ‘Harlequin Sapphire’ has purple and white blooms. ‘Harlequin Rose’ has white lower petals overlaid with deep pink veins.
Most streptocarpus will light up a room for between eight and ten months of the year. If you want to be guaranteed blooms in the depths of winter, there’s only one choice – the ‘Crystal’ series. Among them are ‘Crystal Wonder’ with deep purple flowers with a white throat; pale pink and violet ‘Crystal Dawn’; and pure white ‘Crystal Snow’.
These houseplants prefer a cool room and a light, bright position out of direct sunlight – if it’s too sunny, the leaves will burn and the flowers fade prematurely. An east or westfacing windowsill is ideal. They can be moved outdoors to dappled shade in summer.
Water regularly, allowing the compost to dry completely before giving them any more. Feed with a half-strength, potash liquid fertiliser every month while they are in bloom. Most plants will need a rest over winter, but continue to feed and water ‘Crystal’ varieties.
Keep plants in good shape by snipping off tatty leaves and pinching off individual flowers as they start to fade.
For a range of streptocarpus, try Dibleys Nurseries (dibleys.com).