Thanks Janet! I'm only about 40 miles from the Eastern WA border, so that site is super helpful!
I'm leaning toward Perfoliata, but I'll wait until mine blooms to make sure. In the meantime, I'll study the entries on the site a little more.
http://web.ewu.edu/ewflora/Mon...
There are a couple of pictures in the database here that look more like C. sibirica to me, and that had me confused. The shape of the leaves was all wrong for mine, but now that I've seen pictures of C. sibirica, I wonder if those pictures are attached to the wrong plant? Until about 3 days ago, I had never heard of Miner's Lettuce, so I've got no idea!
Miner's Lettuce (Claytonia perfoliata)