Houseplant · Gesneriaceae
Cape Primrose
Streptocarpus rexii
Give it bright indirect light and careful watering, and Cape primrose flowers for much of the year.
Bright indirect
Every 5–10 days
55–75°F · 13–24°C
USDA 10–11
Overview
Cape primrose belongs to the Gesneriad family and comes from the forests and rocky slopes of South Africa, from Cape Province up into KwaZulu-Natal. It grows from a rosette of long, strappy leaves, and out of that low mound rise slender stems carrying trumpet-shaped flowers. As a houseplant it stays small and tidy, which makes it easy to find a spot for on a windowsill or shelf.
What sets it apart is how long it keeps going. In good light and steady warmth it can bloom for much of the year, not just a single flush in spring. The flowers come in violets, blues, pinks, and whites, often with darker veining or a contrasting throat.
It earns its reputation as an easy plant. The main thing it asks is restraint with the watering can, since wet feet are the one mistake that does real harm. Give it bright light out of direct sun, let the surface dry between drinks, and it rewards you with months of flowers.
Care
The short version: bright indirect light out of harsh sun, water only once the surface has dried and never leave it standing in water, keep it in a free-draining mix at room temperature, and feed with a high-potash food through the growing season.
Light
Give Cape primrose bright but indirect light, the kind of spot near a window where the sun never strikes the leaves directly. It copes with medium light and even part shade, but harsh midday sun scorches the foliage. An east or north-facing sill suits it well.
Water
This is where most plants are lost, so go gently. Let the top of the compost dry before you water again, roughly every 5 to 10 days in the growing season, and water sparingly in winter when the mix is dry. Keep water off the leaves and never let the pot sit in a saucer.
Soil
Use a fertile, free-draining mix, such as a peat-free houseplant or multi-purpose compost. Humus-rich and moisture-holding is good, but it must drain freely. Steer clear of moisture-control composts, which stay far too wet for these roots.
Temperature
Ordinary room warmth suits it, ideally between 55°F and 75°F (13°C to 24°C). It dislikes cold draughts and sudden chills, so keep it away from a frosty window in winter.
Humidity
Average household humidity is fine, so there's no figure to chase. It appreciates a slightly more humid spot than a dry, heated room, but good airflow matters more than misting, which can invite mould on the flowers.
Feeding
Feed every two weeks from spring to early autumn with a high-potash food at half strength, or a specialist streptocarpus feed, which pushes more flowers. A balanced houseplant fertilizer given less often also works. Stop feeding through the winter rest.
Pruning
Pinch off faded flowers as they go over to keep the blooms coming and stop the plant setting seed. After the main flush, cut a mature plant back and let it rest dormant for up to about three months, easing off the water and stopping the feed.
Repotting
Repot in spring only when needed, and move up just one pot size at a time, since this plant flowers better when its roots are a little snug. Roots filling the pot, slower growth, or compost that dries out almost at once all signal it's time.
Size & spacing
Cape primrose stays compact, reaching about 8 to 18 inches (20 to 46 cm) tall and spreading roughly 12 to 18 inches (30 to 46 cm) across. That tidy size makes it an easy fit for a windowsill or a shelf with room for the leaves to fan out.
Troubleshooting
Most Cape primrose trouble traces back to water or air, and it usually shows on the leaves first. Catch the early signs and a fix is simple. Match what you see below, then act before it spreads.
Soft, rotting leaves or a crown that caves in
This is crown and root rot, and it comes from too much water rather than too little. When the compost stays soggy or the pot sits in a full saucer, the leaf bases turn mushy and the plant collapses from the middle. Cut away the affected foliage, let the mix dry out before you water again, and tip the saucer empty so the roots can breathe.
Fix:
- Remove affected foliage with a clean cut
- Allow the compost to dry before watering again
- Empty any standing water from the saucer and improve drainage
Pale, mottled leaves with bugs you can spot
Sap-sucking pests are at work here, and the usual suspects are aphids, mealybugs, thrips, or spider mites. Turn a leaf over and you'll often find them clustered on the undersides, sometimes with fine webbing or little white cottony tufts. Rinse or wipe off a light outbreak, reach for an insecticidal control if they keep coming back, and move the plant away from the others so they don't spread.
Fix:
- Wipe off or rinse away light infestations
- Treat persistent pests with an appropriate insecticidal control
- Isolate the plant to prevent spread
Grey fuzzy mould on the leaves or blooms
That fuzzy grey coating is botrytis, a mould that takes hold in cool, damp, still air. It settles first on spent flowers and tired foliage. Pull off anything affected, open up the air around the plant, and keep water off the leaves so the spores have nowhere damp to land.
Fix:
- Remove and dispose of affected plant parts
- Improve air circulation around the plant
- Avoid overhead watering and reduce humidity around foliage
Toxicity
Good news for a home with animals: Cape primrose is safe. The ASPCA lists it as non-toxic to cats, dogs, and horses, and nothing in it is known to poison other household pets. A stray nibble won't do harm, though it isn't a plant grown to be eaten.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
The ASPCA lists Cape primrose as non-toxic to cats, so a curious nibble shouldn't cause harm.
Dogs None
Dogs can share a room with this plant safely, since the ASPCA places it on its non-toxic list.
Horses None
It's rated non-toxic to horses, one of the three animals the ASPCA checked directly.
Rabbits Safe
No toxic compounds are known in this plant, so a stray mouthful poses no real risk to a rabbit.
Livestock Safe
Grown indoors as a houseplant, it rarely meets farm animals, and nothing in it is known to poison them.
Birds Safe
Pet birds can perch near it without trouble, as the plant carries no recognized toxins.
People Safe
It's harmless to handle, though it isn't grown to be eaten and is best kept off the plate.
Varieties
Most of the Cape primrose you'll meet are hybrids, but two species sit behind them and are worth knowing by name.
Streptocarpus rexii
The classic species from Cape Province to KwaZulu-Natal, with long strappy leaves and trumpet-shaped flowers, and the parent behind most modern hybrids.
Streptocarpus saxorum
A trailing, more compact species with small fleshy leaves and pale violet-blue flowers that takes well to life as an easy houseplant.
How to propagate
Cape primrose is one of the more rewarding plants to multiply, whether you slice up a single leaf or split a crowded clump.
Leaf cuttingsEasy
Spring to early summer · New plantlets develop in about four to six weeks
Streptocarpus is famous for rooting from leaf cuttings, and you can even slice a single leaf into pieces. Cut across a healthy leaf at roughly 5 cm (2 in) intervals and push the sections upright into a free-draining mix of compost and grit. Take them in spring to early summer and new plantlets push up in about four to six weeks.
DivisionEasy
After flowering · A few weeks to establish
Once a clump has grown crowded, you can split it into several plants. Do this after flowering has finished, ease the roots apart into rooted sections, and each piece settles in over a few weeks.
Myths
Cape primrose is just another name for the African violet.
The two are cousins in the Gesneriad family and like much the same care, which is where the mix-up starts. But Cape primrose is the strappy-leaved Streptocarpus with trumpet flowers, while the African violet is a separate plant, Streptocarpus ionanthus, with rounded velvety leaves.