Yellow wild buckwheat is a mat-forming species that grows in exposed, often rocky subalpine and alpine areas. It's roughly similar to cushion buckwheat in size and habit (spreads a little more), but it has bright yellow flowers (often with reddish accents, and fading to red), and the leaves are a silvery green (rather than silver). The flowers form a whimsical 'lollipop' shape on leafless stems, and I think they're delightful. 
 
This species has all the usual attributes of our many wild buckwheats: long-lived, low water, tons of character. However it prefers high elevations, so to thrive on the valley bottom you might consider a location that gets shade in the late late afternoon, or plan to give it a little extra moisture in the hottest part of the summer. Either way, make sure you plant it in well-drained soil. 
 
Plant with silky phacelia, another high elevation plant! But it will play nicely with any of our cushion plants or smaller clumping plants. Good rock garden candidate.
 
 
second image: Matt Lavin from Bozeman, Montana, USA, CC BY-SA 2.0 <https://creativecommons.org/licenses/by-sa/2.0>, via Wikimedia Commons