Some Xanthorrhoeas are desert dwellers but Xanthorrhoea johnsonii is an east coast species native to the sub tropical areas of north east of NSW right up into the tropical areas of north Queensland. It's very common on hilly/rocky ground and appears to need good drainage. I've never seen them in under rainforest canopy, they're in more open woodland or exposed rocky habitats. Humidity in the wet season is very high but even during the dry season it's still reasonably high. Seed sometimes turns up for saler on Ebay and is probably also available from other online sources. But they tend to be slow growers.

Thank you for that info. Now I need to look into whether or not X. johnsonii has potential to be invasive. Melaleucas, Australian Pines and Eucalyptus have been planted here only to become nuisances. As much as I might like the Grass Trees, I don't want to be someone who introduces a problem plant.

Thanks again.

No, I'v got a couple of them growing, have been thriving away for 8 to 10 years and NO sign of any being invasive, mind you, the odd seedling may come up close by the original plant. If you don't want it just pull it up.