Thanks. That looks like a candidate. I just took a picture that shows the leaves more clearly (it's raining here
) and the leaves do seem like a good fit to photos I've found for G. palustre. I'm not so sure about the flowers: all photos of G. palustre appear to show the petals held distinctly separate, while on my plants the petals interleave to give more of a cup shape. Another comments I found elsewhere about G. palustre that gave me pause is that "it produces few leaves", whereas my plants produce quite dense mounds, as exemplified in the photo below. That could be variability within the species; the patterning on the petals is similar, as far as I can tell.