If you want to keep a bird of paradise small, there are a few things you can do. First, you can keep it in a pot that is too small for it. This will stunt its growth. Second, you can prune it regularly. This will keep it from getting too big. Third, you can keep it in a cool environment. This will slow its growth. Fourth, you can fertilize it with a slow-release fertilizer. This will also slow its growth. Fifth, you can water it with distilled water. This will make it grow more slowly. Finally, you can repot it every two years. This will help to keep its roots constrained and its growth under control.