since manzanita always seems to occur at higher elevations, I would suspect it is at least partially elevation dependent?

That has to be the strangest thing I've ever heard.

Marylou, a quick search showed me that some manzanitas are hardy to zone 8. You may want to research different species and pick one that best suits your growing conditions.

By "elevation dependant" I meant that in my explorations of Arizona I have seen certain plants like manzanita only growing above , say 3000 ft elevation. It may be a specific soil need or day temperature need that occurs naturally at the desired elevation range. That is not to say it can't be grown elswhere with like conditions

I live in Benson, AZ. Does this help? I've seen them in the Chiracahua's which is much higher elevation. Our night temps in Dec & Jan range from 15 deg - 25 deg. Thanks.

I don't think manzanitas need elevation, what they need is a certain amount of moisture (the higher you go in AZ, the more precipitation, in general, so there you go).

In California, manzanitas are common in both the coast range and the Sierra foothills. As you go north into Oregon and Washington (more moisture), they become trees rather than shrubs. In Washington, there are many in the Seattle area, which is essentially at sea level.

There are many species with varying needs. See the link attached for more information.

Here is a link that might be useful: Manzanita info