before i moved to california, i i found a ludwigia that grew a nice orange color in my tank(different tank). during the move, the plant got shredded into a thousand tiny little bits, but i managed to save a single stem. i should have moved it into the crazy tank sooner.
this is what it looks like now. as far as i can tell, it is an odd variety of Ludwigia palustris. it has the right leaf shape, and the flowers are similar, but it could very well be a hybrid.
this is what it looked like before the move
after the move, it practically vanished. all my plants got so beat up that i had to spend several days sifting though all the floating pieces leaf by leaf just to find it. same goes for some wild collected M. umbrosum. eventually i did find a piece that would grow, however. this is that plant now, as seen from above.
the odd thing about this stuff is that it loves to spread across the ground. its the only ludwigia i have ever seen that i think could be trained to work as a ground cover. even when i was in north carolina, it seemed more interested in growing out than up.(at least after it got past the vegetation beneath it)