Shepherdia canadensis
 
An extremely drought-tolerant and cold-hardy shrub, the fruits have a nice lemony, sweet/tart taste and have recently earned the label of a "superfruit."
 
The berries are exceptionally rich in vitamin C, with 100 grams providing about three times the daily requirement. They also contain iron, potassium, and phosphorus.
 
Nitrogen-Fixing Bonus!
This non-leguminous, nitrogen-fixing shrub is hardy down to Zone 2.