Much patience and much food, thats the key with strelitzia. And plenty of water while they are leafing.
Unfortunately I live in the UK and mine are still very young, only six years. In a cool summer they will produce only a few leaves even!
If you want to grow strelitzias then make it worth your while and go for the really good ones.
Everyone has had a go at S. reginae, the orange and blue one, get S. nicolai, the giant Strelitzia, it has almost black flower bracts and pure white petals.
Stunning