Suggestions needed for a large,tropical looking shade tree

20 minutes ago, Than said:

Michael do you think Castanospermum australe will also compete with other plants below it? I have read its root system is extensive. Do you have any experience with it?

I don't know, as I've never cultivated it, though I've certainly seen specimens...but it's been a while...and I was usually concentrating on those beautiful and unusual Technicolor flowers in the crown, rather than its growth-habits. Others here will no doubt have much better info to give. As I remember, even though the crown is dense, the leaves are pinnate and so as litter they will probably break up and then disintegrate fairly well, and you might want to research if the species has been investigated for nitrogen-fixing. If it is a nitrogen-fixer, and if you have the appropriate rhizobia in the soil and the tree will nodulate, then any leaf-drop will be rich in nitrogen and fertilize your soil. As far as competition goes, I have no idea, but perhaps very similar to what you would find with any non-allelopathic tree. I just don't really have any info to give you on it, but the resources are probably out there for you to find through google searches of existing studies...and hopefully someone else with experience growing Castanospermum (we have several Australian members here) can answer these questions.