These have me stumped too. The mauve flower has a definite delphinium/monkshood look and feel to it. It was just growing in a perennial border. The white flower is a pondside herbaceous perennial. The general look of the plant suggests a knotweed (Persicaria/Bistorta/Polygonum) but the flower spikes are more like Lysimachia. Any ideas? After some more research I'm starting to think the delphinium may be Delphinium andersonii, or more likely a D. andersonii hybrid.
The third one is Saururus, probably S. cernuus though I'm uncertain as to how it differs from S. chinensis.
The first plant is definitely not Delphinium andersonii... (In this edit, I'm doing a total about-face from what I typed a moment ago saying it didn't look like a Delphinium at all... !) How about Delphinium requienii? Not entirely sure if the flower detail matches but this is a species with shiny, evergreen foliage that appears similar to the plant in question. http://www.lejardindesophie.net/jardinautes/sophie/paplantes/d/delphreq.htm
Thank you all. Saururus cernuus certainly looks to be the correct ID for my pondside plant, and it's growing in the right location, not only beside water but in a garden of American plants. I agree that the overall look of the other plant isn't too delphinium-like, but the flower does look rather like a delphinium, and the plant is clearly Ranunculaceae. It has to be Delphinium or Aconitum. The whole plant was so solid and chunky that I thought it might be a diploid or tetraploid hybrid. Anyhow, Delphinium requienii certainly looks very close to it and as that species is biennial that would explain why it's no longer there.
