The pond is in its 5th year after a rehab project. Very few if any aquatic plants, happy to see this bush with yellow flowers on the bank in an area where roots probably stay wet. I have 3 bushy clusters on the south bank. Came up by themselves. They look nice and if you all agree, I'd like to try to keep them and hope they make it through the winter despite being cut down by the ice and come up no their own in the spring again.
Looking at this again I can see in the first picture that there are some dark green vertical stalks with no branches or flowers. Those are a left over underwater rush or sedge that this new plant seemed to grow out of. You can see the other stalks of the rush better in the 3rd picture. Somehow these busy plants with yellow flowers came up right in the middle of this cluster of 'rush' or reed like stems.
I'm no expert on plants but pretty sure this would fall into the "bog" plant cat, and the leaf structure that I can make out look somewhat similar to smartweed-but that's not what it is, just looks similar structure-wise.
Sorry, I forgot that photobucket is now blurring the pictures on purpose to try to force you to pay them more money.
When home I can post original pictures for clarity. However RAH, some of the pictures online of Bidens Fondosa do look very similar. That might be it. I'll read more about whether this plant named after the devil is something I want in my pond or not
I'm thinking mine might be the 'swamp beggartick' rather than the 'devil's beggartick' variety. This webpage has good pictures and I need to go home and check some of these features. But it looks like a desirable, common, wildflower/bush that dresses up the pond nicely.
Here's another possibility...what I call Oxeye. It has several variations. The big differences would be that Oxeye blooms with very yellow pedals to begin with and does not produce the stick-tights from the center of the flower...