Cyrtanthus is a large genus of the Amaryllidaceae family native to South Africa. A good reference is Graham Duncan's The Amaryllidaceae of Southern Africa written in 2016. Species are found growing in a wide range of habitats including damp bushy stream edges, as epiphytes on other plants, and in near desert conditions. Unfortunately, they are rarely seen in cultivation and are perhaps not sufficiently known, ever to become popular. A few species adapt well to general cultivation, but others require rather different treatment as to resting periods and watering depending on their areas of origin. Their requirements are sometimes so exact, that they will only ever be grown by collectors and specialist growers. My personal opinion is (don't take that as gospel truth) that Cyrtanthus like a steady, long, moderate to warmish growing season, without sudden shocks of very cold periods, which could also spell disaster. Growing Cyrtanthus species was never meant to be easy, (apart from Cyrtanthus elatus and hybrids) but if successful, will be fascinating, rewarding and very enjoyable. Bill Dijk
The requirements of the more difficult species will have to be understood to be successful. That's why I always grow them in (generous) containers (various sizes according to species), not only for convenience, but mainly to control conditions required at the different times of the season. When it comes to watering, when and how much is important as well. I usually water freely when in active growth and flowering, but soon after flowering and seed collecting, growth slows down and so does watering to the point where I keep them barely damp. Too much water combined with too much cold at this time could be detrimental for the plant. BTW: It is a well known fact that many pot plants are lost due to over-watering.
With the potting medium, the main requirement should always be good drainage. Our mix consists of 50% composted bark, 25% pumice and 25% sand, to which I add some well decayed mushroom compost, plus a measure of (9-12 months) slow release, well balanced NPK ( + trace elements), low nitrogen fertiliser. Don't think your results will be magically solved with this (our) medium. I think the climate, the method of cultivation and potting mix together will determine success. It's best to treat each species separately.
Cyrtanthus species seem especially prone to Narcissus bulb fly, at least when grown in California. The larva can attack the bigger bulbs and you may not notice anything wrong until the leaves die back and exploration shows the bulb is soft and being eaten from the inside. Some growers regularly treat their pots with insecticide if they cannot protect the plants.
Cyrtanthus seeds are short-lived and should be treated like fleshy amaryllids. They can be stored in the fridge for up to 6 months. Seeds are often sown on the surface of a well-drained medium and only slightly covered with sand or grit to keep the seeds in place. However, some of our members have better success in floating the seeds until they sprout and then carefully planting them just underneath the medium surface. This is particularly true if your medium is very well-drained and dry out too quickly for the non-floating method. But regardless of what method you choose, the germinating seeds need to be kept moist.
Veld & Flora magazine ran a very detailed series of articles on Cyrtanthus in 1990. They have been reproduced online by the South African National Biodiversity Institute (SANBI). Click on the next page to get all three pages of each article. The articles include cultivation advice and information on the various species and hybrids:
General notes and cultivation
There is also a helpful overview from SANBI.
For photos and information about the species select the appropriate wiki page:
or click on the name in the table below: