Sunset "Western Garden Book" gives only a Hawaiian climate zone for it. Also says, however, "Extremely drought tolerant". Maybe you can keep it going by coddling it, but I suspect it may be vulnerable to the high temperatures, low humidity or alkaline water you may have.

I don't have any personal experience with this plant, but a lot of Hawaiian natives are pretty hard to grow outside their natural habitat. "Trailside Plants of Hawaii's National Parks" says this species is confined to dry lowlands such as the Kalapana region of the Big Island. The soil over there is practically pure cinder, which tends to be slightly acid to neutral; temp. probably not more than 90 deg. F, or less than maybe 55-60 at night, if that. I don't know what it's outer tolerances would be, I guess you'll just have to try it and see. Good luck!

Wiliwili get to be very large trees. True, they are extremely xeric, but also do not do well in cooler climates. The habitat of wiliwili is very dry, coastal leeward locations on the islands.
Aloha

Thank you so much for the info - I appreciate it. Sounds like I'll have to try it as a container plant (maybe that will limit the size?) that can overwinter inside.... hmmm... wish me luck!

Thanks again, and please come visit the AZ forum if there's anything we can help you out with - we seem to have a good number of Hawaiian expats, here, too.