By Lois Scott, Master Gardener
Don’t worry if math isn’t your thing. Multiplying, or more correctly, propagating Streptocarpus (Cape Primrose), a beautiful flowering house plant, is not complicated at all.
If you have a streptocarpus, an efficient way to propagate to get more plants is to take a leaf cutting. The way you prepare a leaf cutting varies somewhat depending on the plant. Check this link for different propagation methods for other plants.
Many plants will root well in water but some, like Streptocarpus, will form stringy, fibrous roots that may have difficulty becoming established when planted in soil. That is why a leaf cutting is advised. It is quite an amazing process as both leaves and roots are formed and the leaf cutting does not become part of the new plant.
You should have all your equipment clean and ready. Take a healthy leaf from a well hydrated plant and either cut out the midrib of the leaf, creating two leaf pieces or cut the leaf into 5cm sections from top to bottom. Have a clean pot already prepared with moistened soilless potting mix or half and half potting mix and perlite (medium). Your moistened medium should still be crumbly, not forming clumps, as that may mean it is too wet and may cause your leaf cutting to rot. Take your leaf cuttings and place them in the soil. Placing them about 2.5cm deep is advised but my leaf cutting wasn’t that big. As you can see parts of the leaf curled up but I still managed to get results. Five plantlets so far!
After your cuttings are in the soil, place your pot in a plastic bag to keep the humidity high. Leaf cuttings have no roots to support them so they need the high humidity. Place your bagged pot in a warm, bright spot but not in direct sun. It is advised to open the bag every week to release excess humidity and to water as needed. You may find you never need to water while the pot is bagged.
In about 6-12 weeks you will hopefully have little plantlets forming. Wait until they have developed enough leaf and root tissue and then pot on to 3-4” pots and enjoy your new plants.
See also this link: https://www.rhs.org.uk/plants/streptocarpus/growing-guide