Streptocarpus Propagation by Seed

Cape primrose (Streptocarpus spp.) grows well as an interior potted plant or as an outdoor plant in U.S. Department of Agriculture plant hardiness zones 10 and 11. The plants produce tubular purple, blue, pink or white flowers on lush foliage particularly well-suited to hanging baskets. Cape primroses germinate readily from seed if sown properly and provided with correct care.

Container Preparation

The small seeds of cape primroses are best started in a wide, shallow seedling flat. This allows you to start multiple seeds in a larger space for later individual potting. Flats must contain bottom drainage holes or slits so excess moisture drains freely from the potting medium. A tray set beneath the flat collects the drainage. A peat-based potting medium formulated for seed starting works best because it is sterile and fine-textured, which helps the seedlings root well. Fill the flat to the rim with the medium, and water it thoroughly until it feels evenly moist throughout.


Cape Primrose seed packets contain about 35,000 seeds per gram, which makes it impossible to sow the seeds individually. Instead, sprinkle seeds thinly on the soil surface and try to plant no more than three seeds per inch. Sprinkling the seeds down the length of the flat in rows set about 2 inches apart makes later thinning easier. Cape primroses require light to germinate, so don't cover the seeds after sowing. Press on the seeds lightly to ensure they are in full contact with the potting medium.


The seeds usually require seven to 10 days to germinate if the medium is kept moist. Misting the soil surface with water and covering it with a sheet of clear plastic retains moisture so the seeds don't require watering until after they germinate. The seeds won't germinate without light, but avoid placing them in direct sun, which can overheat them. Temperatures between 65 and 70 degrees Fahrenheit result in the best germination. Once the seeds sprout, remove the plastic so they are exposed to sufficient air circulation.

Early Care

Once sprouted, cape primroses need lower temperatures -- between 60 and 65 degrees Fahrenheit -- to ensure compact and healthy growth. Provide the seedlings with enough water so the soil remains moist. They need irrigation when the soil surface feels dry. Empty the drip tray after each watering so the soil doesn't reabsorb the moisture and become saturated. The seedlings grow best with six or more hours of bright but indirect sunlight daily. Once the seedlings grow in their second set of leaves, transplant them into individual pots. Lift the seedlings out of the flat by their topmost leaves and pot them at the same depth they were growing in the flat.

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