I know nothing about this, but it looks like it. It's not native here, but it does show up; it's listed as an exotic at E-Flora BC Atlas Page (ubc.ca). The distribution map there brings up records for Lactuca muralis, as does Lactuca muralis - Wikipedia, which shows Mycelis muralis as a synonym. On the E-Flora BC site, a query on Lactuca includes the page for Mycelis muralis.
Bingo. I found this while taking fotos of my Chinese Ground Orchids (Bletilla striat). Trying to get better shots, I removed any weed in the vicinity, then I notice this dinky flowers, which happen to be almost leafless. I shot it and tried to find out the ID. Kept waiting for the forum to reopen and posted it right away. Thanks very much for enlightening me.
