Hi there,
look for the post I responded to about Sea Buckthorn I think that is fairly drought tolerant after it gets established.

Also in terms of medicinal adaptogens rhodiola is a great tonic, especially for the adrenal glands. lots for great uses endurance, stress, fatigue.
I read that it was originally discovered in Siberia? or somewhere in northern Europe, so that a definite yes for cold hardy. My mom has it growing here in BC in zone 5.

Not to sure on where to get seeds, but make sure you are getting quatlity and double check the latin names!
want more plant links? I have lots!

Find out more about rhodiola and where it came form:
rhodiolarosea.org/

And details on cultivation and medicinal uses:
www.pfaf.org/database/plants.php

In my opinion the best first step to take is to get the "Medicinal Plants" field guide for your region of the country and go for a walk. I found dozens and dozens of unique and useful herbs that are perfectly suited to our area.