Mark, without pictures, the most prevalent Ludwigia in our area is Ludwigia palustris. If I had to guess, that’d be it. It’s well-worth trying, is it’s a lovely aquarium plant, and yes, it’s everywhere!

I’ve also got an update for you on the Ludwigia sp. growing in a creek in my neighborhood: it is now the dominant aquatic plant in the creek, growing from one shore to another – it emerses in the middle of the creek, where the water is deeper, but stays submerged in shallower water closer to shore … I’m guessing this may be an adaptation for optimizing photosynthesis – maybe it doesn’t need to emerse in shallower water because sun light penetrates better there? The only problem with this theory of mine is that the shore is also shaded by emersed bog plants such as pickerel and iris, as well as shore-hugging trees such as box elder and willow.
The emersed (Ludwigia) plants have become a deep burgundy hue, which usually extends for at least a couple of inches below the water surface, fading to rusty green; the fully-submerged plants are bright green, sometimes with a slight golden hue. I’m wondering if any of this info effects your guess on the exact species?

Cheers,
Mark