Janet, you did it again! I agree now that you found links so I can see the photos that it is H. littoralis. I tried & tried to get links for photos & could only find a few which didn't have nearly all of them. I don't know how you manage to get these links you do but I sure am glad!
Having the plant in my yard then I was able to look at the photos you provided links for & THEN it was easy to ID it.
Once again.... Janet Super Sleuth to the rescue!
I'll put it in the DB this evening.
Stay tuned ---- I have a complete mystery to me I will post this evening.