Grow in moist but well-drained, deep, humus-rich, fertile soil. Intolerant of waterlogging and may need some protection from frosts in colder areas. Keep neck of the bulb just proud of the soil.
Propagate by seed sown in containers with bottom heat when ripe or by offsets in spring. https://www.rhs.org.uk/plants/90456/crinum-powellii/details
Crinums, also known as swamp lilies, are bulbous perennials and come from sub-tropical areas including South America and South Africa. As their common name suggests, in the wild they’re found growing in boggy, marshy or swampy areas. That said, they don’t like to sit in wet soil all the time. A sunny border with deep, rich, free-draining soil is perfect for them. They love warm moist soil, and a typical UK summer provides just the right amount of both warm and wet conditions for them to thrive. Despite their more exotic origins, they’re quite hardy – they tolerate frost and can cope with a mild winter in sheltered gardens. To be on the safe side, they can easily be lifted and stored in a frost-free place over winter. https://www.farmergracy.co.uk/blogs/farmer-gracys-blog/all-about-crinums